Research ArticleSynthesis Properties and Humidity Resistance Enhancement ofBiodegradable Cellulose-Containing Superabsorbent Polymer
Hongliang Guan Junbo Li Biyu Zhang and Xunmin Yu
School of Chemistry and Environmental Engineering Wuhan Institute of Technology Wuhan 430074 China
Correspondence should be addressed to Junbo Li jbliwit163com
Received 19 August 2016 Revised 12 October 2016 Accepted 14 December 2016 Published 10 January 2017
Academic Editor Dirk Kuckling
Copyright copy 2017 Hongliang Guan et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited
To improve the humidity resistance and water absorption capacity of the superabsorbent polymer (SAP) a biodegradable cellulose-containing polymer was successfully assembled through inverse suspension polymerization using cellulose acrylic acid andacrylamide as monomers Span-80 as dispersant and potassium persulfate as initiator The impact of conditions such as reactiontemperature ratio of oil to water degree of neutralization amount of cellulose and cross-linking agents on the properties of thepolymer were evaluated The results showed that the as-prepared superabsorbent polymer exhibited the best water (859 gg) andsalt water (7248 gg) absorption rate when the reaction temperature was 70∘C monomer ratio was 1 10 neutralization degreewas 75 and oil-water ratio was 3 1 Moreover the humidity resistance of the polymer could be enhanced significantly by addingdifferent cross-linking reagents such as epoxy chloropropane or diethylene glycol
1 Introduction
Superabsorbent polymerwith strong hydrophilic groups suchas carboxyl and hydroxy can absorb water hundreds of timesmore than its own weight in a short time and exhibit goodwater retention even at high temperature and pressure [1ndash4]The superabsorbent polymer is superior to other absorbingmaterials [5 6] It has been widely used in many fields suchas diapers sanitary napkins oilfield chemistry and watersoluble coatings [7ndash10]
The main synthesized methods for the superabsorbentpolymer include bulk polymerization solution polymeriza-tion inverse emulsion polymerization and inverse suspen-sion polymerization Zhang et al [11] synthesized the starchgraft superabsorbent polymer with larger water absorptioncapacity through radical polymerization in aqueous solutionChangchaivong and Khaodhiar [12] prepared a series ofresins using different kinds of monomer by inverse suspen-sion polymerization and the water absorption rate reached730 gg Mahdavinia et al [13] synthesized superabsorbentpolymer of chitosan-graft-acrylamide and the pH depen-dence and swelling property have been fully investigated
The superabsorbent polymer based on cellulose has theadvantages of high gel strength low soluble component con-tent strong water retention ability being biodegradable andhigh enzymolysis resistance [14] Essawy et al [15] obtainedthe acrylic acid and chitosan-cellulose hybrid superabsorbenthydrogels via graft polymerization Fekete et al [16] preparedsuperabsorbent hydrogels from aqueous solutions of fourcellulose derivatives the swelling properties of CMC gelswith lower water uptake showed lower sensitivity to the ionicstrength of the solvent Montesano et al [17] evaluated anovel class of cellulose-based superabsorbent hydrogels foragricultural use the soil moisture at field capacity increasedwith the highest hydrogel percentage up to 400 comparedto the nonamended soil The as-prepared cellulose-basedsuperabsorbent hydrogels showed to be suitable for potentialuse in agriculture Mohammadi-Khoo et al [18] synthesizeda cellulose-based biodegradable hydrogel which exhibitedexcellent swelling behavior in distilled water tap water and09NaCl solution it can be employed as a suitablemoisture-holding additive in the soil for agricultural purposes
However it was easy for the reported cellulose-basedsuperabsorbent polymers to absorb moisture which will
HindawiJournal of PolymersVolume 2017 Article ID 3134681 8 pageshttpsdoiorg10115520173134681
2 Journal of Polymers
seriously affect their translation storage and usage [19]Thus methods to improve the moisture-proof of resins arehighly desirable In this paper the superabsorbent polymerwith high water absorbency and gel strength was preparedunder optimum conditions The ratio of oil to water thedegree of neutralization the amount of cellulose and cross-linking agents on the absorption of water were investigatedFurthermore the moisture-proof ability of the resins aftermodification by different kinds of cross-linking agents wasalso discussed carefully
2 Experimental
21 Materials Carboxymethyl cellulose (CMC chemicallypure TianJin Fucheng Chemical Reagent Factory) cyclo-hexane (analytical grade TianJin Fucheng Chemical Rea-gent Factory) potassium persulfate (analytical grade Shang-hai Kaibo Chemical Reagent Factory) N N1015840-methylene-bisacrylamide (analytical grade Shanghai Kaibo Chemi-cal Reagent Factory) sodium hydroxide (analytical gradeShanghai KaiboChemical Reagent Factory) Span-80 (analyt-ical grade Shanghai Kaibo Chemical Reagent Factory) anhy-drous ethanol (analytical grade Shanghai Kaibo ChemicalReagent Factory) diethylene glycol (analytical grade TianJinFucheng Chemical Reagent Factory) epoxy chloropropane(analytical grade TianJin Fucheng Chemical Reagent Fac-tory) ethylene glycol (analytical grade TianJin FuchengChemical Reagent Factory) polyethylene glycol (analyti-cal grade TianJin Fucheng Chemical Reagent Factory)ethylenediamine (analytical grade TianJin Fucheng Chem-ical Reagent Factory) acrylamide (analytical grade TianJinFuchengChemical Reagent Factory) and acrylic acid (analyt-ical grade TianJin Fucheng Chemical Reagent Factory) weredistilled under reduced pressure before use
22 Synthesis of Superabsorbent Polymer Acertain amount ofcellulose cyclohexane (100 g) acrylic acid (173 g) and acry-lamide (298 g) was added to a four-neck flask equipped withgas line mechanical stirrer condenser and thermometer andstirred at 45∘C for 05 h under nitrogen After the acrylic acidsolution was neutralized by sodium hydroxide aqueous solu-tion the initiating agent potassium persulfate (KPS 008 g)and the cross-linking agent N N1015840-methylenebisacrylamide(MBA 008 g) were added to the mixture Then the systemtemperature was raised to 75∘C and a polymeric gel wasformed Finally the product was washed several times withethanol and dried in vacuumat 100∘C for 10 hThewhite pow-dered superabsorbent polymer was obtained by smashing
23 Infrared Spectrum Fourier Transform Infrared Spec-troscopy (IR) was measured with KBr direct compressionscanning for 5 times at the range of 4000ndash400 cmminus1
24 Measurement of Water and Salt Water Absorbency Thedried powdered resin (01 g) was immersed in 500mL dis-tilled water and 09 physiological saline solution respec-tively The water-swollen gel was filtered by a sieve after
4000 3500 3000 2500 2000 1500 1000 500
SAPCMC
Inte
nsity
(au
)
344189
292784
161837
145809
140674
116687
106869
344844
292330
161833
142486138441
126869
106001
Wavenumbers (cmminus1)
a
b
Figure 1 The IR spectra of CMC and the superabsorbent polymer(SAP)
soaking overnight and then weighted The water-holdingcapacity was calculated by the following equation
119876 =(1198722minus1198721)
1198721
(1)
where1198722is the weight of water-swollen gel119872
1is the weight
of dried sample and 119876 is the water absorbing capacity
25 Experiment for theMoisture Resistance Acertain amountof resin was divided into several groups at random andtiled on the surface of watch glass at 25∘C with humidityof 70 The hygroscopic rate was measured and the curvewas made at different times until the absorption reachedsaturation Moreover the results were compared with thoseof the untreated resin at the same conditions
3 Results and Discussion
31 Infrared SpectrumAnalysis Figure 1 shows the IR spectraof CMC and SAP The peak at 344844 cmminus1 is the stretchingvibration peak of ndashOH groupThe peaks at 292330 cmminus1 and161833 cmminus1 are attributed to CndashH symmetrical stretchingvibration peak and C=O stretching vibration peak respec-tively Compared with the IR spectrum of CMC (Figure 1(a))the peaks at 140674 cmminus1 and 145809 cmminus1 (Figure 1(b)) aredue to the O=C=O and ndashCH
2ndash in-plane bending vibration
which are the characteristic adsorption bands of sodiumpolyacrylate [15] The peak at 116687 cmminus1 is the =CndashOstretching vibration of =CndashOndashC and the peak at 106869 cmminus1is ndashCndashO stretching vibration of CndashOndashC which indicated thatCMC was successfully grafted in SAP
32 Effect of the Amount of Cellulose on the AbsorptionProperties of SAP Figures 2 and 3 show the effect of theamount of cellulose on water and salt water absorptionWhen the monomer ratio was less than 1 10 the water and
Figure 3 Effect of the amount of cellulose on salt water absorptionof superabsorbent polymer
salt water absorption rate significantly increased with theincreasing ratio of the monomer The maximum absorptionrate for water and salt water reached 70614 gg and 7248 ggrespectively However when the monomer ratio exceeded1 10 the absorption rate of SAP for water and salt waterdecreased with the ratio increase The results showed thatthe optimized monomer ratio for the absorption of waterand salt water was 1 10 The possible reason is that withthe monomer ratio increase the viscosity of the reactionsystem increased It weakened the probability of the activecollision between monomers and shortened polyacrylic acidacrylamide graft chains which is adverse to the formation ofpolymer network structure [20ndash24] On the other hand theamount of cellulose is important for the graft polymerizationand too little amount of cellulose has an adverse influence onthe graft polymerization
33 The Effect of Neutralization Degree on the AbsorptionProperties of SAP As shown in Figures 4 and 5 the optimumneutralization degree is 75Thepossible reason is as follows
65 70 75 80 85100
200
300
400
500
600
700
800
The w
ater a
bsor
ptio
n ra
te
The neutralization degree ()
Figure 4The effect of neutralization degree on water absorption ofsuperabsorbent polymer
65 70 75 80 85
20
30
40
50
60
70Th
e salt
wate
r abs
orpt
ion
rate
The neutralization degree ()
Figure 5 Effect of neutralization degree on salt water absorption ofsuperabsorbent polymer
the acidity of the solution increases with the decreasingof neutralization degree which can accelerate the polymer-ization With the increasing of neutralization process theionization of the carboxyl groups on the molecular chainincreased [25] Thus the repulsive force of carboxyl groupsis enhanced which makes the molecular chain become morestraight and the network structure become larger On theother hand the enhancement of affinity and osmotic pressuremake the water and salt water absorption rate increaseFurthermore the ion concentration becomes higher and thehydrogen bond between the water molecule and ion becomesstronger under the neutralization degree larger than 75which limits the freedom of the molecular diffusion andmakes the microporous polymer play insufficient role in thewater and salt water storage [20]
34 Effect of Oil-Water Ratio on the Absorption Propertiesof SAP As shown in Figures 6 and 7 with the increase ofthe oil-water proportion the water absorption rate of theresin took on the trend with increasing firstly and decreasing
4 Journal of Polymers
450
500
550
600
650
700
The w
ater a
bsor
ptio
n ra
te
The oil-water ratio2 1 25 1 3 1 35 1 4 1
Figure 6 Effect of oil-water ratio on the water absorption ofsuperabsorbent polymer
50
55
60
65
70
The s
alt w
ater a
bsor
ptio
n
The oil-water ratio2 1 25 1 3 1 35 1 4 1
Figure 7 Effect of oil-water ratio on the salt water absorption ofsuperabsorbent polymer
afterwards The optimum proportion of oil-water ratio was3 1 When the ratio was higher than 3 1 the water and saltwater absorption decreased obviously This is because theacrylic acid superabsorbent resin contains a large number ofhydrophilic groups which make the SAP fully swelling inwater Actually the ratio of oil to water has larger influenceon the elasticity of hydrophilic groups (such as carboxyland amino groups) and then it controls the swelling degreeof copolymers When the oil-water ratio is relatively highthe water in the aqueous phase can be dispersed into smalldroplets and the water content in the monomer drops islow which induces the polymer difficult to be crossedAccordingly the water absorption capacity decreased Whenthe ratio of oil to water is low the water content in themonomer drops increased the resin macromolecular chaincould be fully extended the cross-linking degree increasedand the water absorption rate decreased too [21]
35 Effect of Reaction Temperature on Absorption Propertiesof SAP Figures 8 and 9 show the effect of reaction temper-ature on the absorption of water and salt water Absolutely
60 65 70 75 80200
300
400
500
600
700
The w
ater a
bsor
ptio
n ra
te
Temperature (∘C)
Figure 8 Effect of the temperature on the water absorption ofsuperabsorbent polymer
20
30
40
50
60
70Th
e salt
wate
r abs
orpt
ion
rate
60 65 70 75 80Temperature (∘C)
Figure 9 Effect of the temperature on the salt water absorption ofsuperabsorbent polymer
the optimum reaction temperature is 70∘C Since the lowreaction temperature reduces the activity of radical slowsdown the decomposition rate of initiator agent decreasesthe concentration of radical and impedes the delivery ofpolymerization reaction chain the prepared SAP with lowreaction temperature shows relatively low molecular weightandwater absorbency As the reaction temperature increasedthe concentration of radical increased the conversion ratio ofmonomer raised and the ability for the absorption of waterand salt water increased However the heat is difficult todissipate under the higher reaction temperature explosivepolymerization easily occurred and gel disks would form
36 Effect of Different Kinds of Cross-Linking Agent on theProperties of SAP Table 1 shows the properties of SAP mod-ified by different kinds of cross-linking agents The resultsshowed that the strength and dispersity of the as-preparedSAP can be improved with the addition of cross-linkingreagent however the water absorption capacity decreased
Journal of Polymers 5
Table 1 The absorption of SAP after modification by different surface cross-linking reagents
Types of cross-linking agents Water absorption rate (gg) Moisture absorption (humidity resistance) Gel strength DispersionBlank 903 Easy Low and viscous PoorEthylene glycol 861 Easy High viscous BetterDiethylene glycol 859 Poor High relatively dry BetterEpoxy chloropropane (ECH) 832 Poor High dry GoodEthylenediamine 878 Easy High viscous BetterPolyethylene glycol 856 Easy High viscous Poor
Table 2 Effect of epoxy chloropropane dosage on the water absorption
Figure 10 The IR comparison of the SAP before and after ECHmodification (a the IR of the SAP before ECH modification b theIR of the SAP modified by ECH)
The possible reason is as follows with the addition of cross-linking reagents in the SAP a coat on the surface of SAP maybe formed through the reaction between the cross-linkingagents and hydrophilic groups on the resin Fortunately themoisture resistance property of superabsorbent polymer wasobviously enhanced when the resin was treated by epoxychloropropane and diethylene glycol
361 Effect of Epoxy Chloropropane (ECH) Dosages on theProperties of SAP Figure 10 shows the spectrum of the SAPbefore and after ECHmodificationThepeak at 610ndash630 cmminus1is the stretching vibration peak of CndashCl which indicated thatepoxy chloropropane was successfully grafted in SAP
Effect of Epoxy Chloropropane Dosages on the Water Absorp-tion Properties of SAP Table 2 shows the results of thewater absorption for the different epoxy chloropropanedosages The water absorption was tested at different massratios of ECH and C
2H5OH (ECHC
2H5OH = 5 10
15 20 25) and water absorption of the resin sig-nificantly decreased with an increasing amount of epoxychloropropane The possible reasons are as follows With
50
40
30
20
0
0
10
200 400 600
Time (min)800
0510152025
1000
The h
ygro
scop
ic ra
te (
)
0
1
Figure 11 Effect of epoxy chloropropane dosages on the moistureperformance of SAP
the increasing of epoxy chloropropane dosage the cross-linking sites strength and density of the SAP increased whilethe molecular weight between net structure site and liquidcapacity of SAP decreased
Effect of Epoxy Chloropropane Dosages on the Moisture Resis-tance of SAP Figure 11 shows the hydroscopicity of SAP withdifferent dosages of epoxy chloropropane To improve themoisture resistance of SAP the surface particles of the resinwere treated by thermal cross-linking to produce a high cross-linking degree coat The SAP was modified by the mixtureof 2mL distilled water 5mL ethanol and different amountof epoxy chloropropane The results showed that with theincreasing amount of epoxy chloropropane the moistureresistance was improved obviously But when the amountwas more than 20 the moisture resistance was no longersignificantly increased
Effect of DistilledWater Quantity on theMoisture Resistance ofSAPAbsolute ethanol was used as hydrophilic solution in theprocess of thermal cross-linking of the resin It was found thatthe effect of the absolute ethanol on the moisture resistanceof SAP was not very good when it was used as solvent The
6 Journal of Polymers
Table 3 Effect of diethylene glycol dosages on the water absorption
Figure 12 Effect of distilled water quantity on the moisture per-formance of SAP
cross-linking agent only reacted with a spot of free hydroxylgroups on the surface of the resin and remaining cross-linking agents vaporized on heating So the cross-linkingeffect was not stable and the moisture resistance was poorHowever adding a small amount of distilled water cross-linking agent would permeate into the resin in the help ofdistilled water the thickness of surface cross-linking andmoisture resistance were increased after heating treatmentDistilled water at different mass ratios (H
2OC2H5OH =
20 40 60 80) was added in the mixture of 15epoxy chloropropane and absolute ethanol and the moistureresistance was tested When the mass ratio of H
2OC2H5OH
reached 40 the SAP exhibited the best moisture resistanceIf the amount of distilled water kept increasing the resinwould swell seriously adhesion among the particles occurredand the moisture resistance reduced The high cross-linkingdensity coat which formed on the particle surface of the resinby epoxy chloropropane treatment increased the strengthand dispersity of the SAP Combined with the dry surface ofresin particles the moisture resistance of resin was improvedto certain extent In conclusion when the mass ratio ofECHC
2H5OH reached 15 and H
2OC2H5OH reached
40 the properties of the SAP were the best (Figure 12)
362 Effect of Diethylene Glycol (DEG) Dosages on the Proper-ties of SAP Figure 13 shows the spectrum of the SAP beforeand after DEG modification The peak at 1114ndash1120 cmminus1 isstretching vibration peak of the ether groups which indicatedthat diethylene glycol was successfully grafted in SAP
Effect of Diethylene Glycol Dosages on the Water AbsorptionProperties of SAP Table 3 shows the results of the waterabsorption for the different diethylene glycol dosages The
1000
a
b
4000 3500 3000 2500 2000 1500
Wavenumber (cmminus1)
Inte
nsity
Figure 13The IR comparison of the SAP before and after diethyleneglycol modification (a the IR of the SAP before DEG modificationb the IR of the SAP modified by DEG)
0
0
200 400 600
Time (min)800 1000
50
40
30
20
10
The h
ydro
scop
ic ra
te (
)
0
135710
Figure 14 The moisture absorption rate of SAP with differentdosage of diglycol modification
water absorption was tested at different mass ratios of ECHand C
2H5OH (ECHC
2H5OH = 0 1 3 7 10)
Obviously the amount of diethylene glycol dosage had a greateffect on the water absorption The results indicated that theparticles in the resin bonded together performed with poordispersivity when the mass ratio of ECHC
2H5OH exceeded
10 (Figure 14)
Effect of Diethylene Glycol Dosages on the Moisture Resistanceof SAP The resin was modified by the mixture of 2mLdistilled water 5mL anhydrous ethyl alcohol and differentamount of diethylene glycol Results showed that the mois-ture resistance improved with the increasing of the amount
Journal of Polymers 7
Table 4 The optimum reaction conditions
The cellulosemonomerratio
Neutralizationdegree
Oil-waterratio
Reactiontemperature
(∘C)
The ratio ofECHC
2H5OH
The ratio ofDEGC
2H5OH
Water absorptionrate (gg)
Salt waterabsorption rate
(gg)1 10 75 3 1 70 15 5 859 7248
0 200 400 600
Time (min)800 1000
2040
6080
0
5
40
30
35
20
25
10
15
The h
ygro
scop
ic ra
te (
)
Figure 15 The moisture absorption rate of SAP with differentdosage of distilled water
of DEG Compared with the resin treated by ECH themoisture resistance of the SAP treated by DEG exhibitedbetter performance in spite of less gel strength and poorerdryness of resin surface Once the amount of DEG was morethan 7 the adhesion would happen among the particles ofresin And it was difficult to granulate after drying
Effect of Distilled Water Quantity on the Moisture Perfor-mance of SAP When distilled water at different mass ratios(H2OC2H5OH = 20 40 60 80) was added the
moisture resistance of the resin which was processed by 5DEG was measured The addition of distilled water had littleinfluence on the treatment of DEG in respect of the factthat the DEG is a hydrophilic agent with great property ofpenetrability it can infiltrate easily without water (Figure 15)
The humidity resistance of the resin improved with theincreasing amount of DEG The water absorption efficiencyreduced and the impact was lower than the resin processedby ECH When the amount of DEG exceeded 10 theparticles among the resin adhered seriously Although themoisture resistance of the resin treated by DEG was betterthan that treated by ECH the gel strength and dispersity wereinferior to it
37 The Optimum Reaction Conditions The optimum reac-tion conditions are as shown in Table 4
4 Conclusions
In this study the superabsorbent polymer has been syn-thesized through inverse suspension polymerization The
absorption experiments for water and salt water showedthat the operating conditions such as monomer dosagesneutralization degree oil-water ratio temperature and thecross-linking agent had great effects on the water absorp-tion The optimum reaction conditions were as follows thecellulose monomer ratio 1 10 neutralization degree 75oil-water ratio 3 1 and reaction temperature 70∘C Thewater and salt water absorption rate can reach as high as859 gg and 7248 gg respectively Moreover the moistureresistance of the resin treated by ECHandDEGwas improvedsignificantly The moisture resistance showed the best whenthe addition of ECH was 15 and it increased with theincreasing amount of DEG but when the dosage of DEGexceeded 5 the particles among the resin adhered seriously
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
This work was supported by the Scientific Research ProgramofHubei Provincial Department of Education (B2015321) andthe Science Research Fund ofWuhan Institute of Technology
References
[1] H Kono and S Fujita ldquoBiodegradable superabsorbent hydro-gels derived from cellulose by esterification crosslinking with1234-butanetetracarboxylic dianhydriderdquo Carbohydrate Poly-mers vol 87 no 4 pp 2582ndash2588 2012
[2] R Ding and K Gong ldquoSuper-absorbent resin preparation uti-lizing spent mushroom substratesrdquo Journal of Applied PolymerScience vol 130 no 2 pp 1098ndash1103 2013
[3] D Wang Z-Q Song and S-B Shang ldquoCharacterizationand biodegradability of amphoteric superabsorbent polymersrdquoJournal of Applied Polymer Science vol 107 no 6 pp 4116ndash41202008
[4] L A Gugliemelli M OWeaver and C R Russell Salt-resistantthickeners comprising base-saponified starch-polyacrylonitrilegraft copolymers US Patent 3425971[P] 1969-2-4
[5] K Kabir H Mirzadeh M J Zohuriaan-Mehr and M DalirildquoChitosan-modified nanoclay-poly(AMPS) nanocompositehydrogels with improved gel strengthrdquo Polymer Internationalvol 58 no 11 pp 1252ndash1259 2009
[6] D Shen T Wang Y Chen M Wang and G Jiang ldquoEffect ofinternal curing with super absorbent polymers on the relativehumidity of early-age concreterdquo Construction and BuildingMaterials vol 99 pp 246ndash253 2015
[7] Y GHan P L Yang Y P Luo SM Ren L X Zhang and L XuldquoPorosity change model for watered super absorbent polymer-treated soilrdquo Environmental Earth Sciences vol 61 no 6 pp1197ndash1205 2010
8 Journal of Polymers
[8] L Zhou Y Wang Z Liu and Q Huang ldquoCharacteristics ofequilibrium kinetics studies for adsorption of Hg(II) Cu(II)and Ni(II) ions by thiourea-modifiedmagnetic chitosan micro-spheresrdquo Journal of Hazardous Materials vol 161 no 2-3 pp995ndash1002 2009
[9] C Chang B Duan J Cai and L Zhang ldquoSuperabsorbenthydrogels based on cellulose for smart swelling and controllabledeliveryrdquo European Polymer Journal vol 46 no 1 pp 92ndash1002010
[10] Y Bulut G Akcay D Elma and I E Serhatli ldquoSynthesis of clay-based superabsorbent composite and its sorption capabilityrdquoJournal of Hazardous Materials vol 171 no 1ndash3 pp 717ndash7232009
[11] J Zhang L Wang and A Wang ldquoPreparation and swellingbehavior of fast-swelling superabsorbent hydrogels based onstarch-g-poly(acrylic acid-co-sodium acrylate)rdquoMacromolecu-lar Materials and Engineering vol 291 no 6 pp 612ndash620 2006
[12] S Changchaivong and S Khaodhiar ldquoAdsorption of naph-thalene and phenanthrene on dodecylpyridinium-modifiedbentoniterdquoApplied Clay Science vol 43 no 3 pp 317ndash321 2009
[13] G R Mahdavinia A Pourjavadi and M J Zohuriaan-MehrldquoA convenient one-step preparation of chitosan-poly(sodiumacrylate-co-acrylamide) hydrogel hybrids with super-swellingpropertiesrdquo Journal of Applied Polymer Science vol 99 no 4pp 1615ndash1619 2006
[14] Y Zhou S Fu L Zhang and H Zhan ldquoSuperabsorbentnanocomposite hydrogels made of carboxylated cellulosenanofibrils and CMC-g-p(AA-co-AM)rdquo Carbohydrate Poly-mers vol 97 no 2 pp 429ndash435 2013
[15] H A EssawyM BM Ghazy F A El-Hai andM FMohamedldquoSuperabsorbent hydrogels via graft polymerization of acrylicacid from chitosan-cellulose hybrid and their potential incontrolled release of soil nutrientsrdquo International Journal ofBiological Macromolecules vol 89 pp 144ndash151 2016
[16] T Fekete J Borsa E Takacs and L Wojnarovits ldquoSynthesisof cellulose-based superabsorbent hydrogels by high-energyirradiation in the presence of crosslinking agentrdquo RadiationPhysics and Chemistry vol 118 pp 114ndash119 2014
[17] F F Montesano A Parente P Santamaria A Sannino and FSerio ldquoBiodegradable superabsorbent hydrogel increaseswaterretention properties of growing media and plant growthrdquoAgriculture and Agricultural Science Procedia vol 4 pp 451ndash458 2015
[18] S Mohammadi-Khoo P N Moghadam A R Fareghi andN Movagharnezhad ldquoSynthesis of a cellulose-based hydrogelnetwork characterization and study of urea fertilizer slowreleaserdquo Journal of Applied Polymer Science vol 133 no 5Article ID 42935 2016
[19] M Bakass J P Bellat A Mokhlisse and G Bertrand ldquoTheadsorption of water vapor on super absorbent product at lowtemperatures and lowmassrdquo Journal of Applied Polymer Sciencevol 100 no 2 pp 1450ndash1456 2006
[20] Y Zhang H Wang C Gao X Li and L Li ldquoHighly orderedmesoporous carbon nanomatrix as a new approach to improvethe oral absorption of the water-insoluble drug simvastatinrdquoEuropean Journal of Pharmaceutical Sciences vol 49 no 5 pp864ndash872 2013
[21] J Slane J Vivanco J Meyer H-L Ploeg and M SquireldquoModification of acrylic bone cement with mesoporous silicananoparticles effects on mechanical fatigue and absorptionpropertiesrdquo Journal of the Mechanical Behavior of BiomedicalMaterials vol 29 pp 451ndash461 2014
[22] J E Mathis Z Bi C A Bridges et al ldquoEnhanced visible-lightabsorption of mesoporous TiO
[23] D Sun W Jiang Y Wang et al ldquoSynthesis and enhancedelectromagnetic wave absorption properties of Fe
3O4ZnO
mesoporous spheresrdquoMRS Proceedings vol 1663 2014[24] W Cui Y Li Y Ma and G Yu ldquoResearch on the dehydration
property of one of super absorbent resin on the swill oilrdquoModern Applied Science vol 4 no 10 article no 71 2010
[25] H Ye J-Q Zhao and Y-H Zhang ldquoNovel degradable super-absorbent materials of silicateacrylic-based polymer hybridsrdquoJournal of Applied Polymer Science vol 91 no 2 pp 936ndash9402004
seriously affect their translation storage and usage [19]Thus methods to improve the moisture-proof of resins arehighly desirable In this paper the superabsorbent polymerwith high water absorbency and gel strength was preparedunder optimum conditions The ratio of oil to water thedegree of neutralization the amount of cellulose and cross-linking agents on the absorption of water were investigatedFurthermore the moisture-proof ability of the resins aftermodification by different kinds of cross-linking agents wasalso discussed carefully
2 Experimental
21 Materials Carboxymethyl cellulose (CMC chemicallypure TianJin Fucheng Chemical Reagent Factory) cyclo-hexane (analytical grade TianJin Fucheng Chemical Rea-gent Factory) potassium persulfate (analytical grade Shang-hai Kaibo Chemical Reagent Factory) N N1015840-methylene-bisacrylamide (analytical grade Shanghai Kaibo Chemi-cal Reagent Factory) sodium hydroxide (analytical gradeShanghai KaiboChemical Reagent Factory) Span-80 (analyt-ical grade Shanghai Kaibo Chemical Reagent Factory) anhy-drous ethanol (analytical grade Shanghai Kaibo ChemicalReagent Factory) diethylene glycol (analytical grade TianJinFucheng Chemical Reagent Factory) epoxy chloropropane(analytical grade TianJin Fucheng Chemical Reagent Fac-tory) ethylene glycol (analytical grade TianJin FuchengChemical Reagent Factory) polyethylene glycol (analyti-cal grade TianJin Fucheng Chemical Reagent Factory)ethylenediamine (analytical grade TianJin Fucheng Chem-ical Reagent Factory) acrylamide (analytical grade TianJinFuchengChemical Reagent Factory) and acrylic acid (analyt-ical grade TianJin Fucheng Chemical Reagent Factory) weredistilled under reduced pressure before use
22 Synthesis of Superabsorbent Polymer Acertain amount ofcellulose cyclohexane (100 g) acrylic acid (173 g) and acry-lamide (298 g) was added to a four-neck flask equipped withgas line mechanical stirrer condenser and thermometer andstirred at 45∘C for 05 h under nitrogen After the acrylic acidsolution was neutralized by sodium hydroxide aqueous solu-tion the initiating agent potassium persulfate (KPS 008 g)and the cross-linking agent N N1015840-methylenebisacrylamide(MBA 008 g) were added to the mixture Then the systemtemperature was raised to 75∘C and a polymeric gel wasformed Finally the product was washed several times withethanol and dried in vacuumat 100∘C for 10 hThewhite pow-dered superabsorbent polymer was obtained by smashing
23 Infrared Spectrum Fourier Transform Infrared Spec-troscopy (IR) was measured with KBr direct compressionscanning for 5 times at the range of 4000ndash400 cmminus1
24 Measurement of Water and Salt Water Absorbency Thedried powdered resin (01 g) was immersed in 500mL dis-tilled water and 09 physiological saline solution respec-tively The water-swollen gel was filtered by a sieve after
4000 3500 3000 2500 2000 1500 1000 500
SAPCMC
Inte
nsity
(au
)
344189
292784
161837
145809
140674
116687
106869
344844
292330
161833
142486138441
126869
106001
Wavenumbers (cmminus1)
a
b
Figure 1 The IR spectra of CMC and the superabsorbent polymer(SAP)
soaking overnight and then weighted The water-holdingcapacity was calculated by the following equation
119876 =(1198722minus1198721)
1198721
(1)
where1198722is the weight of water-swollen gel119872
1is the weight
of dried sample and 119876 is the water absorbing capacity
25 Experiment for theMoisture Resistance Acertain amountof resin was divided into several groups at random andtiled on the surface of watch glass at 25∘C with humidityof 70 The hygroscopic rate was measured and the curvewas made at different times until the absorption reachedsaturation Moreover the results were compared with thoseof the untreated resin at the same conditions
3 Results and Discussion
31 Infrared SpectrumAnalysis Figure 1 shows the IR spectraof CMC and SAP The peak at 344844 cmminus1 is the stretchingvibration peak of ndashOH groupThe peaks at 292330 cmminus1 and161833 cmminus1 are attributed to CndashH symmetrical stretchingvibration peak and C=O stretching vibration peak respec-tively Compared with the IR spectrum of CMC (Figure 1(a))the peaks at 140674 cmminus1 and 145809 cmminus1 (Figure 1(b)) aredue to the O=C=O and ndashCH
2ndash in-plane bending vibration
which are the characteristic adsorption bands of sodiumpolyacrylate [15] The peak at 116687 cmminus1 is the =CndashOstretching vibration of =CndashOndashC and the peak at 106869 cmminus1is ndashCndashO stretching vibration of CndashOndashC which indicated thatCMC was successfully grafted in SAP
32 Effect of the Amount of Cellulose on the AbsorptionProperties of SAP Figures 2 and 3 show the effect of theamount of cellulose on water and salt water absorptionWhen the monomer ratio was less than 1 10 the water and
Figure 3 Effect of the amount of cellulose on salt water absorptionof superabsorbent polymer
salt water absorption rate significantly increased with theincreasing ratio of the monomer The maximum absorptionrate for water and salt water reached 70614 gg and 7248 ggrespectively However when the monomer ratio exceeded1 10 the absorption rate of SAP for water and salt waterdecreased with the ratio increase The results showed thatthe optimized monomer ratio for the absorption of waterand salt water was 1 10 The possible reason is that withthe monomer ratio increase the viscosity of the reactionsystem increased It weakened the probability of the activecollision between monomers and shortened polyacrylic acidacrylamide graft chains which is adverse to the formation ofpolymer network structure [20ndash24] On the other hand theamount of cellulose is important for the graft polymerizationand too little amount of cellulose has an adverse influence onthe graft polymerization
33 The Effect of Neutralization Degree on the AbsorptionProperties of SAP As shown in Figures 4 and 5 the optimumneutralization degree is 75Thepossible reason is as follows
65 70 75 80 85100
200
300
400
500
600
700
800
The w
ater a
bsor
ptio
n ra
te
The neutralization degree ()
Figure 4The effect of neutralization degree on water absorption ofsuperabsorbent polymer
65 70 75 80 85
20
30
40
50
60
70Th
e salt
wate
r abs
orpt
ion
rate
The neutralization degree ()
Figure 5 Effect of neutralization degree on salt water absorption ofsuperabsorbent polymer
the acidity of the solution increases with the decreasingof neutralization degree which can accelerate the polymer-ization With the increasing of neutralization process theionization of the carboxyl groups on the molecular chainincreased [25] Thus the repulsive force of carboxyl groupsis enhanced which makes the molecular chain become morestraight and the network structure become larger On theother hand the enhancement of affinity and osmotic pressuremake the water and salt water absorption rate increaseFurthermore the ion concentration becomes higher and thehydrogen bond between the water molecule and ion becomesstronger under the neutralization degree larger than 75which limits the freedom of the molecular diffusion andmakes the microporous polymer play insufficient role in thewater and salt water storage [20]
34 Effect of Oil-Water Ratio on the Absorption Propertiesof SAP As shown in Figures 6 and 7 with the increase ofthe oil-water proportion the water absorption rate of theresin took on the trend with increasing firstly and decreasing
4 Journal of Polymers
450
500
550
600
650
700
The w
ater a
bsor
ptio
n ra
te
The oil-water ratio2 1 25 1 3 1 35 1 4 1
Figure 6 Effect of oil-water ratio on the water absorption ofsuperabsorbent polymer
50
55
60
65
70
The s
alt w
ater a
bsor
ptio
n
The oil-water ratio2 1 25 1 3 1 35 1 4 1
Figure 7 Effect of oil-water ratio on the salt water absorption ofsuperabsorbent polymer
afterwards The optimum proportion of oil-water ratio was3 1 When the ratio was higher than 3 1 the water and saltwater absorption decreased obviously This is because theacrylic acid superabsorbent resin contains a large number ofhydrophilic groups which make the SAP fully swelling inwater Actually the ratio of oil to water has larger influenceon the elasticity of hydrophilic groups (such as carboxyland amino groups) and then it controls the swelling degreeof copolymers When the oil-water ratio is relatively highthe water in the aqueous phase can be dispersed into smalldroplets and the water content in the monomer drops islow which induces the polymer difficult to be crossedAccordingly the water absorption capacity decreased Whenthe ratio of oil to water is low the water content in themonomer drops increased the resin macromolecular chaincould be fully extended the cross-linking degree increasedand the water absorption rate decreased too [21]
35 Effect of Reaction Temperature on Absorption Propertiesof SAP Figures 8 and 9 show the effect of reaction temper-ature on the absorption of water and salt water Absolutely
60 65 70 75 80200
300
400
500
600
700
The w
ater a
bsor
ptio
n ra
te
Temperature (∘C)
Figure 8 Effect of the temperature on the water absorption ofsuperabsorbent polymer
20
30
40
50
60
70Th
e salt
wate
r abs
orpt
ion
rate
60 65 70 75 80Temperature (∘C)
Figure 9 Effect of the temperature on the salt water absorption ofsuperabsorbent polymer
the optimum reaction temperature is 70∘C Since the lowreaction temperature reduces the activity of radical slowsdown the decomposition rate of initiator agent decreasesthe concentration of radical and impedes the delivery ofpolymerization reaction chain the prepared SAP with lowreaction temperature shows relatively low molecular weightandwater absorbency As the reaction temperature increasedthe concentration of radical increased the conversion ratio ofmonomer raised and the ability for the absorption of waterand salt water increased However the heat is difficult todissipate under the higher reaction temperature explosivepolymerization easily occurred and gel disks would form
36 Effect of Different Kinds of Cross-Linking Agent on theProperties of SAP Table 1 shows the properties of SAP mod-ified by different kinds of cross-linking agents The resultsshowed that the strength and dispersity of the as-preparedSAP can be improved with the addition of cross-linkingreagent however the water absorption capacity decreased
Journal of Polymers 5
Table 1 The absorption of SAP after modification by different surface cross-linking reagents
Types of cross-linking agents Water absorption rate (gg) Moisture absorption (humidity resistance) Gel strength DispersionBlank 903 Easy Low and viscous PoorEthylene glycol 861 Easy High viscous BetterDiethylene glycol 859 Poor High relatively dry BetterEpoxy chloropropane (ECH) 832 Poor High dry GoodEthylenediamine 878 Easy High viscous BetterPolyethylene glycol 856 Easy High viscous Poor
Table 2 Effect of epoxy chloropropane dosage on the water absorption
Figure 10 The IR comparison of the SAP before and after ECHmodification (a the IR of the SAP before ECH modification b theIR of the SAP modified by ECH)
The possible reason is as follows with the addition of cross-linking reagents in the SAP a coat on the surface of SAP maybe formed through the reaction between the cross-linkingagents and hydrophilic groups on the resin Fortunately themoisture resistance property of superabsorbent polymer wasobviously enhanced when the resin was treated by epoxychloropropane and diethylene glycol
361 Effect of Epoxy Chloropropane (ECH) Dosages on theProperties of SAP Figure 10 shows the spectrum of the SAPbefore and after ECHmodificationThepeak at 610ndash630 cmminus1is the stretching vibration peak of CndashCl which indicated thatepoxy chloropropane was successfully grafted in SAP
Effect of Epoxy Chloropropane Dosages on the Water Absorp-tion Properties of SAP Table 2 shows the results of thewater absorption for the different epoxy chloropropanedosages The water absorption was tested at different massratios of ECH and C
2H5OH (ECHC
2H5OH = 5 10
15 20 25) and water absorption of the resin sig-nificantly decreased with an increasing amount of epoxychloropropane The possible reasons are as follows With
50
40
30
20
0
0
10
200 400 600
Time (min)800
0510152025
1000
The h
ygro
scop
ic ra
te (
)
0
1
Figure 11 Effect of epoxy chloropropane dosages on the moistureperformance of SAP
the increasing of epoxy chloropropane dosage the cross-linking sites strength and density of the SAP increased whilethe molecular weight between net structure site and liquidcapacity of SAP decreased
Effect of Epoxy Chloropropane Dosages on the Moisture Resis-tance of SAP Figure 11 shows the hydroscopicity of SAP withdifferent dosages of epoxy chloropropane To improve themoisture resistance of SAP the surface particles of the resinwere treated by thermal cross-linking to produce a high cross-linking degree coat The SAP was modified by the mixtureof 2mL distilled water 5mL ethanol and different amountof epoxy chloropropane The results showed that with theincreasing amount of epoxy chloropropane the moistureresistance was improved obviously But when the amountwas more than 20 the moisture resistance was no longersignificantly increased
Effect of DistilledWater Quantity on theMoisture Resistance ofSAPAbsolute ethanol was used as hydrophilic solution in theprocess of thermal cross-linking of the resin It was found thatthe effect of the absolute ethanol on the moisture resistanceof SAP was not very good when it was used as solvent The
6 Journal of Polymers
Table 3 Effect of diethylene glycol dosages on the water absorption
Figure 12 Effect of distilled water quantity on the moisture per-formance of SAP
cross-linking agent only reacted with a spot of free hydroxylgroups on the surface of the resin and remaining cross-linking agents vaporized on heating So the cross-linkingeffect was not stable and the moisture resistance was poorHowever adding a small amount of distilled water cross-linking agent would permeate into the resin in the help ofdistilled water the thickness of surface cross-linking andmoisture resistance were increased after heating treatmentDistilled water at different mass ratios (H
2OC2H5OH =
20 40 60 80) was added in the mixture of 15epoxy chloropropane and absolute ethanol and the moistureresistance was tested When the mass ratio of H
2OC2H5OH
reached 40 the SAP exhibited the best moisture resistanceIf the amount of distilled water kept increasing the resinwould swell seriously adhesion among the particles occurredand the moisture resistance reduced The high cross-linkingdensity coat which formed on the particle surface of the resinby epoxy chloropropane treatment increased the strengthand dispersity of the SAP Combined with the dry surface ofresin particles the moisture resistance of resin was improvedto certain extent In conclusion when the mass ratio ofECHC
2H5OH reached 15 and H
2OC2H5OH reached
40 the properties of the SAP were the best (Figure 12)
362 Effect of Diethylene Glycol (DEG) Dosages on the Proper-ties of SAP Figure 13 shows the spectrum of the SAP beforeand after DEG modification The peak at 1114ndash1120 cmminus1 isstretching vibration peak of the ether groups which indicatedthat diethylene glycol was successfully grafted in SAP
Effect of Diethylene Glycol Dosages on the Water AbsorptionProperties of SAP Table 3 shows the results of the waterabsorption for the different diethylene glycol dosages The
1000
a
b
4000 3500 3000 2500 2000 1500
Wavenumber (cmminus1)
Inte
nsity
Figure 13The IR comparison of the SAP before and after diethyleneglycol modification (a the IR of the SAP before DEG modificationb the IR of the SAP modified by DEG)
0
0
200 400 600
Time (min)800 1000
50
40
30
20
10
The h
ydro
scop
ic ra
te (
)
0
135710
Figure 14 The moisture absorption rate of SAP with differentdosage of diglycol modification
water absorption was tested at different mass ratios of ECHand C
2H5OH (ECHC
2H5OH = 0 1 3 7 10)
Obviously the amount of diethylene glycol dosage had a greateffect on the water absorption The results indicated that theparticles in the resin bonded together performed with poordispersivity when the mass ratio of ECHC
2H5OH exceeded
10 (Figure 14)
Effect of Diethylene Glycol Dosages on the Moisture Resistanceof SAP The resin was modified by the mixture of 2mLdistilled water 5mL anhydrous ethyl alcohol and differentamount of diethylene glycol Results showed that the mois-ture resistance improved with the increasing of the amount
Journal of Polymers 7
Table 4 The optimum reaction conditions
The cellulosemonomerratio
Neutralizationdegree
Oil-waterratio
Reactiontemperature
(∘C)
The ratio ofECHC
2H5OH
The ratio ofDEGC
2H5OH
Water absorptionrate (gg)
Salt waterabsorption rate
(gg)1 10 75 3 1 70 15 5 859 7248
0 200 400 600
Time (min)800 1000
2040
6080
0
5
40
30
35
20
25
10
15
The h
ygro
scop
ic ra
te (
)
Figure 15 The moisture absorption rate of SAP with differentdosage of distilled water
of DEG Compared with the resin treated by ECH themoisture resistance of the SAP treated by DEG exhibitedbetter performance in spite of less gel strength and poorerdryness of resin surface Once the amount of DEG was morethan 7 the adhesion would happen among the particles ofresin And it was difficult to granulate after drying
Effect of Distilled Water Quantity on the Moisture Perfor-mance of SAP When distilled water at different mass ratios(H2OC2H5OH = 20 40 60 80) was added the
moisture resistance of the resin which was processed by 5DEG was measured The addition of distilled water had littleinfluence on the treatment of DEG in respect of the factthat the DEG is a hydrophilic agent with great property ofpenetrability it can infiltrate easily without water (Figure 15)
The humidity resistance of the resin improved with theincreasing amount of DEG The water absorption efficiencyreduced and the impact was lower than the resin processedby ECH When the amount of DEG exceeded 10 theparticles among the resin adhered seriously Although themoisture resistance of the resin treated by DEG was betterthan that treated by ECH the gel strength and dispersity wereinferior to it
37 The Optimum Reaction Conditions The optimum reac-tion conditions are as shown in Table 4
4 Conclusions
In this study the superabsorbent polymer has been syn-thesized through inverse suspension polymerization The
absorption experiments for water and salt water showedthat the operating conditions such as monomer dosagesneutralization degree oil-water ratio temperature and thecross-linking agent had great effects on the water absorp-tion The optimum reaction conditions were as follows thecellulose monomer ratio 1 10 neutralization degree 75oil-water ratio 3 1 and reaction temperature 70∘C Thewater and salt water absorption rate can reach as high as859 gg and 7248 gg respectively Moreover the moistureresistance of the resin treated by ECHandDEGwas improvedsignificantly The moisture resistance showed the best whenthe addition of ECH was 15 and it increased with theincreasing amount of DEG but when the dosage of DEGexceeded 5 the particles among the resin adhered seriously
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
This work was supported by the Scientific Research ProgramofHubei Provincial Department of Education (B2015321) andthe Science Research Fund ofWuhan Institute of Technology
References
[1] H Kono and S Fujita ldquoBiodegradable superabsorbent hydro-gels derived from cellulose by esterification crosslinking with1234-butanetetracarboxylic dianhydriderdquo Carbohydrate Poly-mers vol 87 no 4 pp 2582ndash2588 2012
[2] R Ding and K Gong ldquoSuper-absorbent resin preparation uti-lizing spent mushroom substratesrdquo Journal of Applied PolymerScience vol 130 no 2 pp 1098ndash1103 2013
[3] D Wang Z-Q Song and S-B Shang ldquoCharacterizationand biodegradability of amphoteric superabsorbent polymersrdquoJournal of Applied Polymer Science vol 107 no 6 pp 4116ndash41202008
[4] L A Gugliemelli M OWeaver and C R Russell Salt-resistantthickeners comprising base-saponified starch-polyacrylonitrilegraft copolymers US Patent 3425971[P] 1969-2-4
[5] K Kabir H Mirzadeh M J Zohuriaan-Mehr and M DalirildquoChitosan-modified nanoclay-poly(AMPS) nanocompositehydrogels with improved gel strengthrdquo Polymer Internationalvol 58 no 11 pp 1252ndash1259 2009
[6] D Shen T Wang Y Chen M Wang and G Jiang ldquoEffect ofinternal curing with super absorbent polymers on the relativehumidity of early-age concreterdquo Construction and BuildingMaterials vol 99 pp 246ndash253 2015
[7] Y GHan P L Yang Y P Luo SM Ren L X Zhang and L XuldquoPorosity change model for watered super absorbent polymer-treated soilrdquo Environmental Earth Sciences vol 61 no 6 pp1197ndash1205 2010
8 Journal of Polymers
[8] L Zhou Y Wang Z Liu and Q Huang ldquoCharacteristics ofequilibrium kinetics studies for adsorption of Hg(II) Cu(II)and Ni(II) ions by thiourea-modifiedmagnetic chitosan micro-spheresrdquo Journal of Hazardous Materials vol 161 no 2-3 pp995ndash1002 2009
[9] C Chang B Duan J Cai and L Zhang ldquoSuperabsorbenthydrogels based on cellulose for smart swelling and controllabledeliveryrdquo European Polymer Journal vol 46 no 1 pp 92ndash1002010
[10] Y Bulut G Akcay D Elma and I E Serhatli ldquoSynthesis of clay-based superabsorbent composite and its sorption capabilityrdquoJournal of Hazardous Materials vol 171 no 1ndash3 pp 717ndash7232009
[11] J Zhang L Wang and A Wang ldquoPreparation and swellingbehavior of fast-swelling superabsorbent hydrogels based onstarch-g-poly(acrylic acid-co-sodium acrylate)rdquoMacromolecu-lar Materials and Engineering vol 291 no 6 pp 612ndash620 2006
[12] S Changchaivong and S Khaodhiar ldquoAdsorption of naph-thalene and phenanthrene on dodecylpyridinium-modifiedbentoniterdquoApplied Clay Science vol 43 no 3 pp 317ndash321 2009
[13] G R Mahdavinia A Pourjavadi and M J Zohuriaan-MehrldquoA convenient one-step preparation of chitosan-poly(sodiumacrylate-co-acrylamide) hydrogel hybrids with super-swellingpropertiesrdquo Journal of Applied Polymer Science vol 99 no 4pp 1615ndash1619 2006
[14] Y Zhou S Fu L Zhang and H Zhan ldquoSuperabsorbentnanocomposite hydrogels made of carboxylated cellulosenanofibrils and CMC-g-p(AA-co-AM)rdquo Carbohydrate Poly-mers vol 97 no 2 pp 429ndash435 2013
[15] H A EssawyM BM Ghazy F A El-Hai andM FMohamedldquoSuperabsorbent hydrogels via graft polymerization of acrylicacid from chitosan-cellulose hybrid and their potential incontrolled release of soil nutrientsrdquo International Journal ofBiological Macromolecules vol 89 pp 144ndash151 2016
[16] T Fekete J Borsa E Takacs and L Wojnarovits ldquoSynthesisof cellulose-based superabsorbent hydrogels by high-energyirradiation in the presence of crosslinking agentrdquo RadiationPhysics and Chemistry vol 118 pp 114ndash119 2014
[17] F F Montesano A Parente P Santamaria A Sannino and FSerio ldquoBiodegradable superabsorbent hydrogel increaseswaterretention properties of growing media and plant growthrdquoAgriculture and Agricultural Science Procedia vol 4 pp 451ndash458 2015
[18] S Mohammadi-Khoo P N Moghadam A R Fareghi andN Movagharnezhad ldquoSynthesis of a cellulose-based hydrogelnetwork characterization and study of urea fertilizer slowreleaserdquo Journal of Applied Polymer Science vol 133 no 5Article ID 42935 2016
[19] M Bakass J P Bellat A Mokhlisse and G Bertrand ldquoTheadsorption of water vapor on super absorbent product at lowtemperatures and lowmassrdquo Journal of Applied Polymer Sciencevol 100 no 2 pp 1450ndash1456 2006
[20] Y Zhang H Wang C Gao X Li and L Li ldquoHighly orderedmesoporous carbon nanomatrix as a new approach to improvethe oral absorption of the water-insoluble drug simvastatinrdquoEuropean Journal of Pharmaceutical Sciences vol 49 no 5 pp864ndash872 2013
[21] J Slane J Vivanco J Meyer H-L Ploeg and M SquireldquoModification of acrylic bone cement with mesoporous silicananoparticles effects on mechanical fatigue and absorptionpropertiesrdquo Journal of the Mechanical Behavior of BiomedicalMaterials vol 29 pp 451ndash461 2014
[22] J E Mathis Z Bi C A Bridges et al ldquoEnhanced visible-lightabsorption of mesoporous TiO
[23] D Sun W Jiang Y Wang et al ldquoSynthesis and enhancedelectromagnetic wave absorption properties of Fe
3O4ZnO
mesoporous spheresrdquoMRS Proceedings vol 1663 2014[24] W Cui Y Li Y Ma and G Yu ldquoResearch on the dehydration
property of one of super absorbent resin on the swill oilrdquoModern Applied Science vol 4 no 10 article no 71 2010
[25] H Ye J-Q Zhao and Y-H Zhang ldquoNovel degradable super-absorbent materials of silicateacrylic-based polymer hybridsrdquoJournal of Applied Polymer Science vol 91 no 2 pp 936ndash9402004
Figure 3 Effect of the amount of cellulose on salt water absorptionof superabsorbent polymer
salt water absorption rate significantly increased with theincreasing ratio of the monomer The maximum absorptionrate for water and salt water reached 70614 gg and 7248 ggrespectively However when the monomer ratio exceeded1 10 the absorption rate of SAP for water and salt waterdecreased with the ratio increase The results showed thatthe optimized monomer ratio for the absorption of waterand salt water was 1 10 The possible reason is that withthe monomer ratio increase the viscosity of the reactionsystem increased It weakened the probability of the activecollision between monomers and shortened polyacrylic acidacrylamide graft chains which is adverse to the formation ofpolymer network structure [20ndash24] On the other hand theamount of cellulose is important for the graft polymerizationand too little amount of cellulose has an adverse influence onthe graft polymerization
33 The Effect of Neutralization Degree on the AbsorptionProperties of SAP As shown in Figures 4 and 5 the optimumneutralization degree is 75Thepossible reason is as follows
65 70 75 80 85100
200
300
400
500
600
700
800
The w
ater a
bsor
ptio
n ra
te
The neutralization degree ()
Figure 4The effect of neutralization degree on water absorption ofsuperabsorbent polymer
65 70 75 80 85
20
30
40
50
60
70Th
e salt
wate
r abs
orpt
ion
rate
The neutralization degree ()
Figure 5 Effect of neutralization degree on salt water absorption ofsuperabsorbent polymer
the acidity of the solution increases with the decreasingof neutralization degree which can accelerate the polymer-ization With the increasing of neutralization process theionization of the carboxyl groups on the molecular chainincreased [25] Thus the repulsive force of carboxyl groupsis enhanced which makes the molecular chain become morestraight and the network structure become larger On theother hand the enhancement of affinity and osmotic pressuremake the water and salt water absorption rate increaseFurthermore the ion concentration becomes higher and thehydrogen bond between the water molecule and ion becomesstronger under the neutralization degree larger than 75which limits the freedom of the molecular diffusion andmakes the microporous polymer play insufficient role in thewater and salt water storage [20]
34 Effect of Oil-Water Ratio on the Absorption Propertiesof SAP As shown in Figures 6 and 7 with the increase ofthe oil-water proportion the water absorption rate of theresin took on the trend with increasing firstly and decreasing
4 Journal of Polymers
450
500
550
600
650
700
The w
ater a
bsor
ptio
n ra
te
The oil-water ratio2 1 25 1 3 1 35 1 4 1
Figure 6 Effect of oil-water ratio on the water absorption ofsuperabsorbent polymer
50
55
60
65
70
The s
alt w
ater a
bsor
ptio
n
The oil-water ratio2 1 25 1 3 1 35 1 4 1
Figure 7 Effect of oil-water ratio on the salt water absorption ofsuperabsorbent polymer
afterwards The optimum proportion of oil-water ratio was3 1 When the ratio was higher than 3 1 the water and saltwater absorption decreased obviously This is because theacrylic acid superabsorbent resin contains a large number ofhydrophilic groups which make the SAP fully swelling inwater Actually the ratio of oil to water has larger influenceon the elasticity of hydrophilic groups (such as carboxyland amino groups) and then it controls the swelling degreeof copolymers When the oil-water ratio is relatively highthe water in the aqueous phase can be dispersed into smalldroplets and the water content in the monomer drops islow which induces the polymer difficult to be crossedAccordingly the water absorption capacity decreased Whenthe ratio of oil to water is low the water content in themonomer drops increased the resin macromolecular chaincould be fully extended the cross-linking degree increasedand the water absorption rate decreased too [21]
35 Effect of Reaction Temperature on Absorption Propertiesof SAP Figures 8 and 9 show the effect of reaction temper-ature on the absorption of water and salt water Absolutely
60 65 70 75 80200
300
400
500
600
700
The w
ater a
bsor
ptio
n ra
te
Temperature (∘C)
Figure 8 Effect of the temperature on the water absorption ofsuperabsorbent polymer
20
30
40
50
60
70Th
e salt
wate
r abs
orpt
ion
rate
60 65 70 75 80Temperature (∘C)
Figure 9 Effect of the temperature on the salt water absorption ofsuperabsorbent polymer
the optimum reaction temperature is 70∘C Since the lowreaction temperature reduces the activity of radical slowsdown the decomposition rate of initiator agent decreasesthe concentration of radical and impedes the delivery ofpolymerization reaction chain the prepared SAP with lowreaction temperature shows relatively low molecular weightandwater absorbency As the reaction temperature increasedthe concentration of radical increased the conversion ratio ofmonomer raised and the ability for the absorption of waterand salt water increased However the heat is difficult todissipate under the higher reaction temperature explosivepolymerization easily occurred and gel disks would form
36 Effect of Different Kinds of Cross-Linking Agent on theProperties of SAP Table 1 shows the properties of SAP mod-ified by different kinds of cross-linking agents The resultsshowed that the strength and dispersity of the as-preparedSAP can be improved with the addition of cross-linkingreagent however the water absorption capacity decreased
Journal of Polymers 5
Table 1 The absorption of SAP after modification by different surface cross-linking reagents
Types of cross-linking agents Water absorption rate (gg) Moisture absorption (humidity resistance) Gel strength DispersionBlank 903 Easy Low and viscous PoorEthylene glycol 861 Easy High viscous BetterDiethylene glycol 859 Poor High relatively dry BetterEpoxy chloropropane (ECH) 832 Poor High dry GoodEthylenediamine 878 Easy High viscous BetterPolyethylene glycol 856 Easy High viscous Poor
Table 2 Effect of epoxy chloropropane dosage on the water absorption
Figure 10 The IR comparison of the SAP before and after ECHmodification (a the IR of the SAP before ECH modification b theIR of the SAP modified by ECH)
The possible reason is as follows with the addition of cross-linking reagents in the SAP a coat on the surface of SAP maybe formed through the reaction between the cross-linkingagents and hydrophilic groups on the resin Fortunately themoisture resistance property of superabsorbent polymer wasobviously enhanced when the resin was treated by epoxychloropropane and diethylene glycol
361 Effect of Epoxy Chloropropane (ECH) Dosages on theProperties of SAP Figure 10 shows the spectrum of the SAPbefore and after ECHmodificationThepeak at 610ndash630 cmminus1is the stretching vibration peak of CndashCl which indicated thatepoxy chloropropane was successfully grafted in SAP
Effect of Epoxy Chloropropane Dosages on the Water Absorp-tion Properties of SAP Table 2 shows the results of thewater absorption for the different epoxy chloropropanedosages The water absorption was tested at different massratios of ECH and C
2H5OH (ECHC
2H5OH = 5 10
15 20 25) and water absorption of the resin sig-nificantly decreased with an increasing amount of epoxychloropropane The possible reasons are as follows With
50
40
30
20
0
0
10
200 400 600
Time (min)800
0510152025
1000
The h
ygro
scop
ic ra
te (
)
0
1
Figure 11 Effect of epoxy chloropropane dosages on the moistureperformance of SAP
the increasing of epoxy chloropropane dosage the cross-linking sites strength and density of the SAP increased whilethe molecular weight between net structure site and liquidcapacity of SAP decreased
Effect of Epoxy Chloropropane Dosages on the Moisture Resis-tance of SAP Figure 11 shows the hydroscopicity of SAP withdifferent dosages of epoxy chloropropane To improve themoisture resistance of SAP the surface particles of the resinwere treated by thermal cross-linking to produce a high cross-linking degree coat The SAP was modified by the mixtureof 2mL distilled water 5mL ethanol and different amountof epoxy chloropropane The results showed that with theincreasing amount of epoxy chloropropane the moistureresistance was improved obviously But when the amountwas more than 20 the moisture resistance was no longersignificantly increased
Effect of DistilledWater Quantity on theMoisture Resistance ofSAPAbsolute ethanol was used as hydrophilic solution in theprocess of thermal cross-linking of the resin It was found thatthe effect of the absolute ethanol on the moisture resistanceof SAP was not very good when it was used as solvent The
6 Journal of Polymers
Table 3 Effect of diethylene glycol dosages on the water absorption
Figure 12 Effect of distilled water quantity on the moisture per-formance of SAP
cross-linking agent only reacted with a spot of free hydroxylgroups on the surface of the resin and remaining cross-linking agents vaporized on heating So the cross-linkingeffect was not stable and the moisture resistance was poorHowever adding a small amount of distilled water cross-linking agent would permeate into the resin in the help ofdistilled water the thickness of surface cross-linking andmoisture resistance were increased after heating treatmentDistilled water at different mass ratios (H
2OC2H5OH =
20 40 60 80) was added in the mixture of 15epoxy chloropropane and absolute ethanol and the moistureresistance was tested When the mass ratio of H
2OC2H5OH
reached 40 the SAP exhibited the best moisture resistanceIf the amount of distilled water kept increasing the resinwould swell seriously adhesion among the particles occurredand the moisture resistance reduced The high cross-linkingdensity coat which formed on the particle surface of the resinby epoxy chloropropane treatment increased the strengthand dispersity of the SAP Combined with the dry surface ofresin particles the moisture resistance of resin was improvedto certain extent In conclusion when the mass ratio ofECHC
2H5OH reached 15 and H
2OC2H5OH reached
40 the properties of the SAP were the best (Figure 12)
362 Effect of Diethylene Glycol (DEG) Dosages on the Proper-ties of SAP Figure 13 shows the spectrum of the SAP beforeand after DEG modification The peak at 1114ndash1120 cmminus1 isstretching vibration peak of the ether groups which indicatedthat diethylene glycol was successfully grafted in SAP
Effect of Diethylene Glycol Dosages on the Water AbsorptionProperties of SAP Table 3 shows the results of the waterabsorption for the different diethylene glycol dosages The
1000
a
b
4000 3500 3000 2500 2000 1500
Wavenumber (cmminus1)
Inte
nsity
Figure 13The IR comparison of the SAP before and after diethyleneglycol modification (a the IR of the SAP before DEG modificationb the IR of the SAP modified by DEG)
0
0
200 400 600
Time (min)800 1000
50
40
30
20
10
The h
ydro
scop
ic ra
te (
)
0
135710
Figure 14 The moisture absorption rate of SAP with differentdosage of diglycol modification
water absorption was tested at different mass ratios of ECHand C
2H5OH (ECHC
2H5OH = 0 1 3 7 10)
Obviously the amount of diethylene glycol dosage had a greateffect on the water absorption The results indicated that theparticles in the resin bonded together performed with poordispersivity when the mass ratio of ECHC
2H5OH exceeded
10 (Figure 14)
Effect of Diethylene Glycol Dosages on the Moisture Resistanceof SAP The resin was modified by the mixture of 2mLdistilled water 5mL anhydrous ethyl alcohol and differentamount of diethylene glycol Results showed that the mois-ture resistance improved with the increasing of the amount
Journal of Polymers 7
Table 4 The optimum reaction conditions
The cellulosemonomerratio
Neutralizationdegree
Oil-waterratio
Reactiontemperature
(∘C)
The ratio ofECHC
2H5OH
The ratio ofDEGC
2H5OH
Water absorptionrate (gg)
Salt waterabsorption rate
(gg)1 10 75 3 1 70 15 5 859 7248
0 200 400 600
Time (min)800 1000
2040
6080
0
5
40
30
35
20
25
10
15
The h
ygro
scop
ic ra
te (
)
Figure 15 The moisture absorption rate of SAP with differentdosage of distilled water
of DEG Compared with the resin treated by ECH themoisture resistance of the SAP treated by DEG exhibitedbetter performance in spite of less gel strength and poorerdryness of resin surface Once the amount of DEG was morethan 7 the adhesion would happen among the particles ofresin And it was difficult to granulate after drying
Effect of Distilled Water Quantity on the Moisture Perfor-mance of SAP When distilled water at different mass ratios(H2OC2H5OH = 20 40 60 80) was added the
moisture resistance of the resin which was processed by 5DEG was measured The addition of distilled water had littleinfluence on the treatment of DEG in respect of the factthat the DEG is a hydrophilic agent with great property ofpenetrability it can infiltrate easily without water (Figure 15)
The humidity resistance of the resin improved with theincreasing amount of DEG The water absorption efficiencyreduced and the impact was lower than the resin processedby ECH When the amount of DEG exceeded 10 theparticles among the resin adhered seriously Although themoisture resistance of the resin treated by DEG was betterthan that treated by ECH the gel strength and dispersity wereinferior to it
37 The Optimum Reaction Conditions The optimum reac-tion conditions are as shown in Table 4
4 Conclusions
In this study the superabsorbent polymer has been syn-thesized through inverse suspension polymerization The
absorption experiments for water and salt water showedthat the operating conditions such as monomer dosagesneutralization degree oil-water ratio temperature and thecross-linking agent had great effects on the water absorp-tion The optimum reaction conditions were as follows thecellulose monomer ratio 1 10 neutralization degree 75oil-water ratio 3 1 and reaction temperature 70∘C Thewater and salt water absorption rate can reach as high as859 gg and 7248 gg respectively Moreover the moistureresistance of the resin treated by ECHandDEGwas improvedsignificantly The moisture resistance showed the best whenthe addition of ECH was 15 and it increased with theincreasing amount of DEG but when the dosage of DEGexceeded 5 the particles among the resin adhered seriously
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
This work was supported by the Scientific Research ProgramofHubei Provincial Department of Education (B2015321) andthe Science Research Fund ofWuhan Institute of Technology
References
[1] H Kono and S Fujita ldquoBiodegradable superabsorbent hydro-gels derived from cellulose by esterification crosslinking with1234-butanetetracarboxylic dianhydriderdquo Carbohydrate Poly-mers vol 87 no 4 pp 2582ndash2588 2012
[2] R Ding and K Gong ldquoSuper-absorbent resin preparation uti-lizing spent mushroom substratesrdquo Journal of Applied PolymerScience vol 130 no 2 pp 1098ndash1103 2013
[3] D Wang Z-Q Song and S-B Shang ldquoCharacterizationand biodegradability of amphoteric superabsorbent polymersrdquoJournal of Applied Polymer Science vol 107 no 6 pp 4116ndash41202008
[4] L A Gugliemelli M OWeaver and C R Russell Salt-resistantthickeners comprising base-saponified starch-polyacrylonitrilegraft copolymers US Patent 3425971[P] 1969-2-4
[5] K Kabir H Mirzadeh M J Zohuriaan-Mehr and M DalirildquoChitosan-modified nanoclay-poly(AMPS) nanocompositehydrogels with improved gel strengthrdquo Polymer Internationalvol 58 no 11 pp 1252ndash1259 2009
[6] D Shen T Wang Y Chen M Wang and G Jiang ldquoEffect ofinternal curing with super absorbent polymers on the relativehumidity of early-age concreterdquo Construction and BuildingMaterials vol 99 pp 246ndash253 2015
[7] Y GHan P L Yang Y P Luo SM Ren L X Zhang and L XuldquoPorosity change model for watered super absorbent polymer-treated soilrdquo Environmental Earth Sciences vol 61 no 6 pp1197ndash1205 2010
8 Journal of Polymers
[8] L Zhou Y Wang Z Liu and Q Huang ldquoCharacteristics ofequilibrium kinetics studies for adsorption of Hg(II) Cu(II)and Ni(II) ions by thiourea-modifiedmagnetic chitosan micro-spheresrdquo Journal of Hazardous Materials vol 161 no 2-3 pp995ndash1002 2009
[9] C Chang B Duan J Cai and L Zhang ldquoSuperabsorbenthydrogels based on cellulose for smart swelling and controllabledeliveryrdquo European Polymer Journal vol 46 no 1 pp 92ndash1002010
[10] Y Bulut G Akcay D Elma and I E Serhatli ldquoSynthesis of clay-based superabsorbent composite and its sorption capabilityrdquoJournal of Hazardous Materials vol 171 no 1ndash3 pp 717ndash7232009
[11] J Zhang L Wang and A Wang ldquoPreparation and swellingbehavior of fast-swelling superabsorbent hydrogels based onstarch-g-poly(acrylic acid-co-sodium acrylate)rdquoMacromolecu-lar Materials and Engineering vol 291 no 6 pp 612ndash620 2006
[12] S Changchaivong and S Khaodhiar ldquoAdsorption of naph-thalene and phenanthrene on dodecylpyridinium-modifiedbentoniterdquoApplied Clay Science vol 43 no 3 pp 317ndash321 2009
[13] G R Mahdavinia A Pourjavadi and M J Zohuriaan-MehrldquoA convenient one-step preparation of chitosan-poly(sodiumacrylate-co-acrylamide) hydrogel hybrids with super-swellingpropertiesrdquo Journal of Applied Polymer Science vol 99 no 4pp 1615ndash1619 2006
[14] Y Zhou S Fu L Zhang and H Zhan ldquoSuperabsorbentnanocomposite hydrogels made of carboxylated cellulosenanofibrils and CMC-g-p(AA-co-AM)rdquo Carbohydrate Poly-mers vol 97 no 2 pp 429ndash435 2013
[15] H A EssawyM BM Ghazy F A El-Hai andM FMohamedldquoSuperabsorbent hydrogels via graft polymerization of acrylicacid from chitosan-cellulose hybrid and their potential incontrolled release of soil nutrientsrdquo International Journal ofBiological Macromolecules vol 89 pp 144ndash151 2016
[16] T Fekete J Borsa E Takacs and L Wojnarovits ldquoSynthesisof cellulose-based superabsorbent hydrogels by high-energyirradiation in the presence of crosslinking agentrdquo RadiationPhysics and Chemistry vol 118 pp 114ndash119 2014
[17] F F Montesano A Parente P Santamaria A Sannino and FSerio ldquoBiodegradable superabsorbent hydrogel increaseswaterretention properties of growing media and plant growthrdquoAgriculture and Agricultural Science Procedia vol 4 pp 451ndash458 2015
[18] S Mohammadi-Khoo P N Moghadam A R Fareghi andN Movagharnezhad ldquoSynthesis of a cellulose-based hydrogelnetwork characterization and study of urea fertilizer slowreleaserdquo Journal of Applied Polymer Science vol 133 no 5Article ID 42935 2016
[19] M Bakass J P Bellat A Mokhlisse and G Bertrand ldquoTheadsorption of water vapor on super absorbent product at lowtemperatures and lowmassrdquo Journal of Applied Polymer Sciencevol 100 no 2 pp 1450ndash1456 2006
[20] Y Zhang H Wang C Gao X Li and L Li ldquoHighly orderedmesoporous carbon nanomatrix as a new approach to improvethe oral absorption of the water-insoluble drug simvastatinrdquoEuropean Journal of Pharmaceutical Sciences vol 49 no 5 pp864ndash872 2013
[21] J Slane J Vivanco J Meyer H-L Ploeg and M SquireldquoModification of acrylic bone cement with mesoporous silicananoparticles effects on mechanical fatigue and absorptionpropertiesrdquo Journal of the Mechanical Behavior of BiomedicalMaterials vol 29 pp 451ndash461 2014
[22] J E Mathis Z Bi C A Bridges et al ldquoEnhanced visible-lightabsorption of mesoporous TiO
[23] D Sun W Jiang Y Wang et al ldquoSynthesis and enhancedelectromagnetic wave absorption properties of Fe
3O4ZnO
mesoporous spheresrdquoMRS Proceedings vol 1663 2014[24] W Cui Y Li Y Ma and G Yu ldquoResearch on the dehydration
property of one of super absorbent resin on the swill oilrdquoModern Applied Science vol 4 no 10 article no 71 2010
[25] H Ye J-Q Zhao and Y-H Zhang ldquoNovel degradable super-absorbent materials of silicateacrylic-based polymer hybridsrdquoJournal of Applied Polymer Science vol 91 no 2 pp 936ndash9402004
Figure 6 Effect of oil-water ratio on the water absorption ofsuperabsorbent polymer
50
55
60
65
70
The s
alt w
ater a
bsor
ptio
n
The oil-water ratio2 1 25 1 3 1 35 1 4 1
Figure 7 Effect of oil-water ratio on the salt water absorption ofsuperabsorbent polymer
afterwards The optimum proportion of oil-water ratio was3 1 When the ratio was higher than 3 1 the water and saltwater absorption decreased obviously This is because theacrylic acid superabsorbent resin contains a large number ofhydrophilic groups which make the SAP fully swelling inwater Actually the ratio of oil to water has larger influenceon the elasticity of hydrophilic groups (such as carboxyland amino groups) and then it controls the swelling degreeof copolymers When the oil-water ratio is relatively highthe water in the aqueous phase can be dispersed into smalldroplets and the water content in the monomer drops islow which induces the polymer difficult to be crossedAccordingly the water absorption capacity decreased Whenthe ratio of oil to water is low the water content in themonomer drops increased the resin macromolecular chaincould be fully extended the cross-linking degree increasedand the water absorption rate decreased too [21]
35 Effect of Reaction Temperature on Absorption Propertiesof SAP Figures 8 and 9 show the effect of reaction temper-ature on the absorption of water and salt water Absolutely
60 65 70 75 80200
300
400
500
600
700
The w
ater a
bsor
ptio
n ra
te
Temperature (∘C)
Figure 8 Effect of the temperature on the water absorption ofsuperabsorbent polymer
20
30
40
50
60
70Th
e salt
wate
r abs
orpt
ion
rate
60 65 70 75 80Temperature (∘C)
Figure 9 Effect of the temperature on the salt water absorption ofsuperabsorbent polymer
the optimum reaction temperature is 70∘C Since the lowreaction temperature reduces the activity of radical slowsdown the decomposition rate of initiator agent decreasesthe concentration of radical and impedes the delivery ofpolymerization reaction chain the prepared SAP with lowreaction temperature shows relatively low molecular weightandwater absorbency As the reaction temperature increasedthe concentration of radical increased the conversion ratio ofmonomer raised and the ability for the absorption of waterand salt water increased However the heat is difficult todissipate under the higher reaction temperature explosivepolymerization easily occurred and gel disks would form
36 Effect of Different Kinds of Cross-Linking Agent on theProperties of SAP Table 1 shows the properties of SAP mod-ified by different kinds of cross-linking agents The resultsshowed that the strength and dispersity of the as-preparedSAP can be improved with the addition of cross-linkingreagent however the water absorption capacity decreased
Journal of Polymers 5
Table 1 The absorption of SAP after modification by different surface cross-linking reagents
Types of cross-linking agents Water absorption rate (gg) Moisture absorption (humidity resistance) Gel strength DispersionBlank 903 Easy Low and viscous PoorEthylene glycol 861 Easy High viscous BetterDiethylene glycol 859 Poor High relatively dry BetterEpoxy chloropropane (ECH) 832 Poor High dry GoodEthylenediamine 878 Easy High viscous BetterPolyethylene glycol 856 Easy High viscous Poor
Table 2 Effect of epoxy chloropropane dosage on the water absorption
Figure 10 The IR comparison of the SAP before and after ECHmodification (a the IR of the SAP before ECH modification b theIR of the SAP modified by ECH)
The possible reason is as follows with the addition of cross-linking reagents in the SAP a coat on the surface of SAP maybe formed through the reaction between the cross-linkingagents and hydrophilic groups on the resin Fortunately themoisture resistance property of superabsorbent polymer wasobviously enhanced when the resin was treated by epoxychloropropane and diethylene glycol
361 Effect of Epoxy Chloropropane (ECH) Dosages on theProperties of SAP Figure 10 shows the spectrum of the SAPbefore and after ECHmodificationThepeak at 610ndash630 cmminus1is the stretching vibration peak of CndashCl which indicated thatepoxy chloropropane was successfully grafted in SAP
Effect of Epoxy Chloropropane Dosages on the Water Absorp-tion Properties of SAP Table 2 shows the results of thewater absorption for the different epoxy chloropropanedosages The water absorption was tested at different massratios of ECH and C
2H5OH (ECHC
2H5OH = 5 10
15 20 25) and water absorption of the resin sig-nificantly decreased with an increasing amount of epoxychloropropane The possible reasons are as follows With
50
40
30
20
0
0
10
200 400 600
Time (min)800
0510152025
1000
The h
ygro
scop
ic ra
te (
)
0
1
Figure 11 Effect of epoxy chloropropane dosages on the moistureperformance of SAP
the increasing of epoxy chloropropane dosage the cross-linking sites strength and density of the SAP increased whilethe molecular weight between net structure site and liquidcapacity of SAP decreased
Effect of Epoxy Chloropropane Dosages on the Moisture Resis-tance of SAP Figure 11 shows the hydroscopicity of SAP withdifferent dosages of epoxy chloropropane To improve themoisture resistance of SAP the surface particles of the resinwere treated by thermal cross-linking to produce a high cross-linking degree coat The SAP was modified by the mixtureof 2mL distilled water 5mL ethanol and different amountof epoxy chloropropane The results showed that with theincreasing amount of epoxy chloropropane the moistureresistance was improved obviously But when the amountwas more than 20 the moisture resistance was no longersignificantly increased
Effect of DistilledWater Quantity on theMoisture Resistance ofSAPAbsolute ethanol was used as hydrophilic solution in theprocess of thermal cross-linking of the resin It was found thatthe effect of the absolute ethanol on the moisture resistanceof SAP was not very good when it was used as solvent The
6 Journal of Polymers
Table 3 Effect of diethylene glycol dosages on the water absorption
Figure 12 Effect of distilled water quantity on the moisture per-formance of SAP
cross-linking agent only reacted with a spot of free hydroxylgroups on the surface of the resin and remaining cross-linking agents vaporized on heating So the cross-linkingeffect was not stable and the moisture resistance was poorHowever adding a small amount of distilled water cross-linking agent would permeate into the resin in the help ofdistilled water the thickness of surface cross-linking andmoisture resistance were increased after heating treatmentDistilled water at different mass ratios (H
2OC2H5OH =
20 40 60 80) was added in the mixture of 15epoxy chloropropane and absolute ethanol and the moistureresistance was tested When the mass ratio of H
2OC2H5OH
reached 40 the SAP exhibited the best moisture resistanceIf the amount of distilled water kept increasing the resinwould swell seriously adhesion among the particles occurredand the moisture resistance reduced The high cross-linkingdensity coat which formed on the particle surface of the resinby epoxy chloropropane treatment increased the strengthand dispersity of the SAP Combined with the dry surface ofresin particles the moisture resistance of resin was improvedto certain extent In conclusion when the mass ratio ofECHC
2H5OH reached 15 and H
2OC2H5OH reached
40 the properties of the SAP were the best (Figure 12)
362 Effect of Diethylene Glycol (DEG) Dosages on the Proper-ties of SAP Figure 13 shows the spectrum of the SAP beforeand after DEG modification The peak at 1114ndash1120 cmminus1 isstretching vibration peak of the ether groups which indicatedthat diethylene glycol was successfully grafted in SAP
Effect of Diethylene Glycol Dosages on the Water AbsorptionProperties of SAP Table 3 shows the results of the waterabsorption for the different diethylene glycol dosages The
1000
a
b
4000 3500 3000 2500 2000 1500
Wavenumber (cmminus1)
Inte
nsity
Figure 13The IR comparison of the SAP before and after diethyleneglycol modification (a the IR of the SAP before DEG modificationb the IR of the SAP modified by DEG)
0
0
200 400 600
Time (min)800 1000
50
40
30
20
10
The h
ydro
scop
ic ra
te (
)
0
135710
Figure 14 The moisture absorption rate of SAP with differentdosage of diglycol modification
water absorption was tested at different mass ratios of ECHand C
2H5OH (ECHC
2H5OH = 0 1 3 7 10)
Obviously the amount of diethylene glycol dosage had a greateffect on the water absorption The results indicated that theparticles in the resin bonded together performed with poordispersivity when the mass ratio of ECHC
2H5OH exceeded
10 (Figure 14)
Effect of Diethylene Glycol Dosages on the Moisture Resistanceof SAP The resin was modified by the mixture of 2mLdistilled water 5mL anhydrous ethyl alcohol and differentamount of diethylene glycol Results showed that the mois-ture resistance improved with the increasing of the amount
Journal of Polymers 7
Table 4 The optimum reaction conditions
The cellulosemonomerratio
Neutralizationdegree
Oil-waterratio
Reactiontemperature
(∘C)
The ratio ofECHC
2H5OH
The ratio ofDEGC
2H5OH
Water absorptionrate (gg)
Salt waterabsorption rate
(gg)1 10 75 3 1 70 15 5 859 7248
0 200 400 600
Time (min)800 1000
2040
6080
0
5
40
30
35
20
25
10
15
The h
ygro
scop
ic ra
te (
)
Figure 15 The moisture absorption rate of SAP with differentdosage of distilled water
of DEG Compared with the resin treated by ECH themoisture resistance of the SAP treated by DEG exhibitedbetter performance in spite of less gel strength and poorerdryness of resin surface Once the amount of DEG was morethan 7 the adhesion would happen among the particles ofresin And it was difficult to granulate after drying
Effect of Distilled Water Quantity on the Moisture Perfor-mance of SAP When distilled water at different mass ratios(H2OC2H5OH = 20 40 60 80) was added the
moisture resistance of the resin which was processed by 5DEG was measured The addition of distilled water had littleinfluence on the treatment of DEG in respect of the factthat the DEG is a hydrophilic agent with great property ofpenetrability it can infiltrate easily without water (Figure 15)
The humidity resistance of the resin improved with theincreasing amount of DEG The water absorption efficiencyreduced and the impact was lower than the resin processedby ECH When the amount of DEG exceeded 10 theparticles among the resin adhered seriously Although themoisture resistance of the resin treated by DEG was betterthan that treated by ECH the gel strength and dispersity wereinferior to it
37 The Optimum Reaction Conditions The optimum reac-tion conditions are as shown in Table 4
4 Conclusions
In this study the superabsorbent polymer has been syn-thesized through inverse suspension polymerization The
absorption experiments for water and salt water showedthat the operating conditions such as monomer dosagesneutralization degree oil-water ratio temperature and thecross-linking agent had great effects on the water absorp-tion The optimum reaction conditions were as follows thecellulose monomer ratio 1 10 neutralization degree 75oil-water ratio 3 1 and reaction temperature 70∘C Thewater and salt water absorption rate can reach as high as859 gg and 7248 gg respectively Moreover the moistureresistance of the resin treated by ECHandDEGwas improvedsignificantly The moisture resistance showed the best whenthe addition of ECH was 15 and it increased with theincreasing amount of DEG but when the dosage of DEGexceeded 5 the particles among the resin adhered seriously
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
This work was supported by the Scientific Research ProgramofHubei Provincial Department of Education (B2015321) andthe Science Research Fund ofWuhan Institute of Technology
References
[1] H Kono and S Fujita ldquoBiodegradable superabsorbent hydro-gels derived from cellulose by esterification crosslinking with1234-butanetetracarboxylic dianhydriderdquo Carbohydrate Poly-mers vol 87 no 4 pp 2582ndash2588 2012
[2] R Ding and K Gong ldquoSuper-absorbent resin preparation uti-lizing spent mushroom substratesrdquo Journal of Applied PolymerScience vol 130 no 2 pp 1098ndash1103 2013
[3] D Wang Z-Q Song and S-B Shang ldquoCharacterizationand biodegradability of amphoteric superabsorbent polymersrdquoJournal of Applied Polymer Science vol 107 no 6 pp 4116ndash41202008
[4] L A Gugliemelli M OWeaver and C R Russell Salt-resistantthickeners comprising base-saponified starch-polyacrylonitrilegraft copolymers US Patent 3425971[P] 1969-2-4
[5] K Kabir H Mirzadeh M J Zohuriaan-Mehr and M DalirildquoChitosan-modified nanoclay-poly(AMPS) nanocompositehydrogels with improved gel strengthrdquo Polymer Internationalvol 58 no 11 pp 1252ndash1259 2009
[6] D Shen T Wang Y Chen M Wang and G Jiang ldquoEffect ofinternal curing with super absorbent polymers on the relativehumidity of early-age concreterdquo Construction and BuildingMaterials vol 99 pp 246ndash253 2015
[7] Y GHan P L Yang Y P Luo SM Ren L X Zhang and L XuldquoPorosity change model for watered super absorbent polymer-treated soilrdquo Environmental Earth Sciences vol 61 no 6 pp1197ndash1205 2010
8 Journal of Polymers
[8] L Zhou Y Wang Z Liu and Q Huang ldquoCharacteristics ofequilibrium kinetics studies for adsorption of Hg(II) Cu(II)and Ni(II) ions by thiourea-modifiedmagnetic chitosan micro-spheresrdquo Journal of Hazardous Materials vol 161 no 2-3 pp995ndash1002 2009
[9] C Chang B Duan J Cai and L Zhang ldquoSuperabsorbenthydrogels based on cellulose for smart swelling and controllabledeliveryrdquo European Polymer Journal vol 46 no 1 pp 92ndash1002010
[10] Y Bulut G Akcay D Elma and I E Serhatli ldquoSynthesis of clay-based superabsorbent composite and its sorption capabilityrdquoJournal of Hazardous Materials vol 171 no 1ndash3 pp 717ndash7232009
[11] J Zhang L Wang and A Wang ldquoPreparation and swellingbehavior of fast-swelling superabsorbent hydrogels based onstarch-g-poly(acrylic acid-co-sodium acrylate)rdquoMacromolecu-lar Materials and Engineering vol 291 no 6 pp 612ndash620 2006
[12] S Changchaivong and S Khaodhiar ldquoAdsorption of naph-thalene and phenanthrene on dodecylpyridinium-modifiedbentoniterdquoApplied Clay Science vol 43 no 3 pp 317ndash321 2009
[13] G R Mahdavinia A Pourjavadi and M J Zohuriaan-MehrldquoA convenient one-step preparation of chitosan-poly(sodiumacrylate-co-acrylamide) hydrogel hybrids with super-swellingpropertiesrdquo Journal of Applied Polymer Science vol 99 no 4pp 1615ndash1619 2006
[14] Y Zhou S Fu L Zhang and H Zhan ldquoSuperabsorbentnanocomposite hydrogels made of carboxylated cellulosenanofibrils and CMC-g-p(AA-co-AM)rdquo Carbohydrate Poly-mers vol 97 no 2 pp 429ndash435 2013
[15] H A EssawyM BM Ghazy F A El-Hai andM FMohamedldquoSuperabsorbent hydrogels via graft polymerization of acrylicacid from chitosan-cellulose hybrid and their potential incontrolled release of soil nutrientsrdquo International Journal ofBiological Macromolecules vol 89 pp 144ndash151 2016
[16] T Fekete J Borsa E Takacs and L Wojnarovits ldquoSynthesisof cellulose-based superabsorbent hydrogels by high-energyirradiation in the presence of crosslinking agentrdquo RadiationPhysics and Chemistry vol 118 pp 114ndash119 2014
[17] F F Montesano A Parente P Santamaria A Sannino and FSerio ldquoBiodegradable superabsorbent hydrogel increaseswaterretention properties of growing media and plant growthrdquoAgriculture and Agricultural Science Procedia vol 4 pp 451ndash458 2015
[18] S Mohammadi-Khoo P N Moghadam A R Fareghi andN Movagharnezhad ldquoSynthesis of a cellulose-based hydrogelnetwork characterization and study of urea fertilizer slowreleaserdquo Journal of Applied Polymer Science vol 133 no 5Article ID 42935 2016
[19] M Bakass J P Bellat A Mokhlisse and G Bertrand ldquoTheadsorption of water vapor on super absorbent product at lowtemperatures and lowmassrdquo Journal of Applied Polymer Sciencevol 100 no 2 pp 1450ndash1456 2006
[20] Y Zhang H Wang C Gao X Li and L Li ldquoHighly orderedmesoporous carbon nanomatrix as a new approach to improvethe oral absorption of the water-insoluble drug simvastatinrdquoEuropean Journal of Pharmaceutical Sciences vol 49 no 5 pp864ndash872 2013
[21] J Slane J Vivanco J Meyer H-L Ploeg and M SquireldquoModification of acrylic bone cement with mesoporous silicananoparticles effects on mechanical fatigue and absorptionpropertiesrdquo Journal of the Mechanical Behavior of BiomedicalMaterials vol 29 pp 451ndash461 2014
[22] J E Mathis Z Bi C A Bridges et al ldquoEnhanced visible-lightabsorption of mesoporous TiO
[23] D Sun W Jiang Y Wang et al ldquoSynthesis and enhancedelectromagnetic wave absorption properties of Fe
3O4ZnO
mesoporous spheresrdquoMRS Proceedings vol 1663 2014[24] W Cui Y Li Y Ma and G Yu ldquoResearch on the dehydration
property of one of super absorbent resin on the swill oilrdquoModern Applied Science vol 4 no 10 article no 71 2010
[25] H Ye J-Q Zhao and Y-H Zhang ldquoNovel degradable super-absorbent materials of silicateacrylic-based polymer hybridsrdquoJournal of Applied Polymer Science vol 91 no 2 pp 936ndash9402004
Figure 10 The IR comparison of the SAP before and after ECHmodification (a the IR of the SAP before ECH modification b theIR of the SAP modified by ECH)
The possible reason is as follows with the addition of cross-linking reagents in the SAP a coat on the surface of SAP maybe formed through the reaction between the cross-linkingagents and hydrophilic groups on the resin Fortunately themoisture resistance property of superabsorbent polymer wasobviously enhanced when the resin was treated by epoxychloropropane and diethylene glycol
361 Effect of Epoxy Chloropropane (ECH) Dosages on theProperties of SAP Figure 10 shows the spectrum of the SAPbefore and after ECHmodificationThepeak at 610ndash630 cmminus1is the stretching vibration peak of CndashCl which indicated thatepoxy chloropropane was successfully grafted in SAP
Effect of Epoxy Chloropropane Dosages on the Water Absorp-tion Properties of SAP Table 2 shows the results of thewater absorption for the different epoxy chloropropanedosages The water absorption was tested at different massratios of ECH and C
2H5OH (ECHC
2H5OH = 5 10
15 20 25) and water absorption of the resin sig-nificantly decreased with an increasing amount of epoxychloropropane The possible reasons are as follows With
50
40
30
20
0
0
10
200 400 600
Time (min)800
0510152025
1000
The h
ygro
scop
ic ra
te (
)
0
1
Figure 11 Effect of epoxy chloropropane dosages on the moistureperformance of SAP
the increasing of epoxy chloropropane dosage the cross-linking sites strength and density of the SAP increased whilethe molecular weight between net structure site and liquidcapacity of SAP decreased
Effect of Epoxy Chloropropane Dosages on the Moisture Resis-tance of SAP Figure 11 shows the hydroscopicity of SAP withdifferent dosages of epoxy chloropropane To improve themoisture resistance of SAP the surface particles of the resinwere treated by thermal cross-linking to produce a high cross-linking degree coat The SAP was modified by the mixtureof 2mL distilled water 5mL ethanol and different amountof epoxy chloropropane The results showed that with theincreasing amount of epoxy chloropropane the moistureresistance was improved obviously But when the amountwas more than 20 the moisture resistance was no longersignificantly increased
Effect of DistilledWater Quantity on theMoisture Resistance ofSAPAbsolute ethanol was used as hydrophilic solution in theprocess of thermal cross-linking of the resin It was found thatthe effect of the absolute ethanol on the moisture resistanceof SAP was not very good when it was used as solvent The
6 Journal of Polymers
Table 3 Effect of diethylene glycol dosages on the water absorption
Figure 12 Effect of distilled water quantity on the moisture per-formance of SAP
cross-linking agent only reacted with a spot of free hydroxylgroups on the surface of the resin and remaining cross-linking agents vaporized on heating So the cross-linkingeffect was not stable and the moisture resistance was poorHowever adding a small amount of distilled water cross-linking agent would permeate into the resin in the help ofdistilled water the thickness of surface cross-linking andmoisture resistance were increased after heating treatmentDistilled water at different mass ratios (H
2OC2H5OH =
20 40 60 80) was added in the mixture of 15epoxy chloropropane and absolute ethanol and the moistureresistance was tested When the mass ratio of H
2OC2H5OH
reached 40 the SAP exhibited the best moisture resistanceIf the amount of distilled water kept increasing the resinwould swell seriously adhesion among the particles occurredand the moisture resistance reduced The high cross-linkingdensity coat which formed on the particle surface of the resinby epoxy chloropropane treatment increased the strengthand dispersity of the SAP Combined with the dry surface ofresin particles the moisture resistance of resin was improvedto certain extent In conclusion when the mass ratio ofECHC
2H5OH reached 15 and H
2OC2H5OH reached
40 the properties of the SAP were the best (Figure 12)
362 Effect of Diethylene Glycol (DEG) Dosages on the Proper-ties of SAP Figure 13 shows the spectrum of the SAP beforeand after DEG modification The peak at 1114ndash1120 cmminus1 isstretching vibration peak of the ether groups which indicatedthat diethylene glycol was successfully grafted in SAP
Effect of Diethylene Glycol Dosages on the Water AbsorptionProperties of SAP Table 3 shows the results of the waterabsorption for the different diethylene glycol dosages The
1000
a
b
4000 3500 3000 2500 2000 1500
Wavenumber (cmminus1)
Inte
nsity
Figure 13The IR comparison of the SAP before and after diethyleneglycol modification (a the IR of the SAP before DEG modificationb the IR of the SAP modified by DEG)
0
0
200 400 600
Time (min)800 1000
50
40
30
20
10
The h
ydro
scop
ic ra
te (
)
0
135710
Figure 14 The moisture absorption rate of SAP with differentdosage of diglycol modification
water absorption was tested at different mass ratios of ECHand C
2H5OH (ECHC
2H5OH = 0 1 3 7 10)
Obviously the amount of diethylene glycol dosage had a greateffect on the water absorption The results indicated that theparticles in the resin bonded together performed with poordispersivity when the mass ratio of ECHC
2H5OH exceeded
10 (Figure 14)
Effect of Diethylene Glycol Dosages on the Moisture Resistanceof SAP The resin was modified by the mixture of 2mLdistilled water 5mL anhydrous ethyl alcohol and differentamount of diethylene glycol Results showed that the mois-ture resistance improved with the increasing of the amount
Journal of Polymers 7
Table 4 The optimum reaction conditions
The cellulosemonomerratio
Neutralizationdegree
Oil-waterratio
Reactiontemperature
(∘C)
The ratio ofECHC
2H5OH
The ratio ofDEGC
2H5OH
Water absorptionrate (gg)
Salt waterabsorption rate
(gg)1 10 75 3 1 70 15 5 859 7248
0 200 400 600
Time (min)800 1000
2040
6080
0
5
40
30
35
20
25
10
15
The h
ygro
scop
ic ra
te (
)
Figure 15 The moisture absorption rate of SAP with differentdosage of distilled water
of DEG Compared with the resin treated by ECH themoisture resistance of the SAP treated by DEG exhibitedbetter performance in spite of less gel strength and poorerdryness of resin surface Once the amount of DEG was morethan 7 the adhesion would happen among the particles ofresin And it was difficult to granulate after drying
Effect of Distilled Water Quantity on the Moisture Perfor-mance of SAP When distilled water at different mass ratios(H2OC2H5OH = 20 40 60 80) was added the
moisture resistance of the resin which was processed by 5DEG was measured The addition of distilled water had littleinfluence on the treatment of DEG in respect of the factthat the DEG is a hydrophilic agent with great property ofpenetrability it can infiltrate easily without water (Figure 15)
The humidity resistance of the resin improved with theincreasing amount of DEG The water absorption efficiencyreduced and the impact was lower than the resin processedby ECH When the amount of DEG exceeded 10 theparticles among the resin adhered seriously Although themoisture resistance of the resin treated by DEG was betterthan that treated by ECH the gel strength and dispersity wereinferior to it
37 The Optimum Reaction Conditions The optimum reac-tion conditions are as shown in Table 4
4 Conclusions
In this study the superabsorbent polymer has been syn-thesized through inverse suspension polymerization The
absorption experiments for water and salt water showedthat the operating conditions such as monomer dosagesneutralization degree oil-water ratio temperature and thecross-linking agent had great effects on the water absorp-tion The optimum reaction conditions were as follows thecellulose monomer ratio 1 10 neutralization degree 75oil-water ratio 3 1 and reaction temperature 70∘C Thewater and salt water absorption rate can reach as high as859 gg and 7248 gg respectively Moreover the moistureresistance of the resin treated by ECHandDEGwas improvedsignificantly The moisture resistance showed the best whenthe addition of ECH was 15 and it increased with theincreasing amount of DEG but when the dosage of DEGexceeded 5 the particles among the resin adhered seriously
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
This work was supported by the Scientific Research ProgramofHubei Provincial Department of Education (B2015321) andthe Science Research Fund ofWuhan Institute of Technology
References
[1] H Kono and S Fujita ldquoBiodegradable superabsorbent hydro-gels derived from cellulose by esterification crosslinking with1234-butanetetracarboxylic dianhydriderdquo Carbohydrate Poly-mers vol 87 no 4 pp 2582ndash2588 2012
[2] R Ding and K Gong ldquoSuper-absorbent resin preparation uti-lizing spent mushroom substratesrdquo Journal of Applied PolymerScience vol 130 no 2 pp 1098ndash1103 2013
[3] D Wang Z-Q Song and S-B Shang ldquoCharacterizationand biodegradability of amphoteric superabsorbent polymersrdquoJournal of Applied Polymer Science vol 107 no 6 pp 4116ndash41202008
[4] L A Gugliemelli M OWeaver and C R Russell Salt-resistantthickeners comprising base-saponified starch-polyacrylonitrilegraft copolymers US Patent 3425971[P] 1969-2-4
[5] K Kabir H Mirzadeh M J Zohuriaan-Mehr and M DalirildquoChitosan-modified nanoclay-poly(AMPS) nanocompositehydrogels with improved gel strengthrdquo Polymer Internationalvol 58 no 11 pp 1252ndash1259 2009
[6] D Shen T Wang Y Chen M Wang and G Jiang ldquoEffect ofinternal curing with super absorbent polymers on the relativehumidity of early-age concreterdquo Construction and BuildingMaterials vol 99 pp 246ndash253 2015
[7] Y GHan P L Yang Y P Luo SM Ren L X Zhang and L XuldquoPorosity change model for watered super absorbent polymer-treated soilrdquo Environmental Earth Sciences vol 61 no 6 pp1197ndash1205 2010
8 Journal of Polymers
[8] L Zhou Y Wang Z Liu and Q Huang ldquoCharacteristics ofequilibrium kinetics studies for adsorption of Hg(II) Cu(II)and Ni(II) ions by thiourea-modifiedmagnetic chitosan micro-spheresrdquo Journal of Hazardous Materials vol 161 no 2-3 pp995ndash1002 2009
[9] C Chang B Duan J Cai and L Zhang ldquoSuperabsorbenthydrogels based on cellulose for smart swelling and controllabledeliveryrdquo European Polymer Journal vol 46 no 1 pp 92ndash1002010
[10] Y Bulut G Akcay D Elma and I E Serhatli ldquoSynthesis of clay-based superabsorbent composite and its sorption capabilityrdquoJournal of Hazardous Materials vol 171 no 1ndash3 pp 717ndash7232009
[11] J Zhang L Wang and A Wang ldquoPreparation and swellingbehavior of fast-swelling superabsorbent hydrogels based onstarch-g-poly(acrylic acid-co-sodium acrylate)rdquoMacromolecu-lar Materials and Engineering vol 291 no 6 pp 612ndash620 2006
[12] S Changchaivong and S Khaodhiar ldquoAdsorption of naph-thalene and phenanthrene on dodecylpyridinium-modifiedbentoniterdquoApplied Clay Science vol 43 no 3 pp 317ndash321 2009
[13] G R Mahdavinia A Pourjavadi and M J Zohuriaan-MehrldquoA convenient one-step preparation of chitosan-poly(sodiumacrylate-co-acrylamide) hydrogel hybrids with super-swellingpropertiesrdquo Journal of Applied Polymer Science vol 99 no 4pp 1615ndash1619 2006
[14] Y Zhou S Fu L Zhang and H Zhan ldquoSuperabsorbentnanocomposite hydrogels made of carboxylated cellulosenanofibrils and CMC-g-p(AA-co-AM)rdquo Carbohydrate Poly-mers vol 97 no 2 pp 429ndash435 2013
[15] H A EssawyM BM Ghazy F A El-Hai andM FMohamedldquoSuperabsorbent hydrogels via graft polymerization of acrylicacid from chitosan-cellulose hybrid and their potential incontrolled release of soil nutrientsrdquo International Journal ofBiological Macromolecules vol 89 pp 144ndash151 2016
[16] T Fekete J Borsa E Takacs and L Wojnarovits ldquoSynthesisof cellulose-based superabsorbent hydrogels by high-energyirradiation in the presence of crosslinking agentrdquo RadiationPhysics and Chemistry vol 118 pp 114ndash119 2014
[17] F F Montesano A Parente P Santamaria A Sannino and FSerio ldquoBiodegradable superabsorbent hydrogel increaseswaterretention properties of growing media and plant growthrdquoAgriculture and Agricultural Science Procedia vol 4 pp 451ndash458 2015
[18] S Mohammadi-Khoo P N Moghadam A R Fareghi andN Movagharnezhad ldquoSynthesis of a cellulose-based hydrogelnetwork characterization and study of urea fertilizer slowreleaserdquo Journal of Applied Polymer Science vol 133 no 5Article ID 42935 2016
[19] M Bakass J P Bellat A Mokhlisse and G Bertrand ldquoTheadsorption of water vapor on super absorbent product at lowtemperatures and lowmassrdquo Journal of Applied Polymer Sciencevol 100 no 2 pp 1450ndash1456 2006
[20] Y Zhang H Wang C Gao X Li and L Li ldquoHighly orderedmesoporous carbon nanomatrix as a new approach to improvethe oral absorption of the water-insoluble drug simvastatinrdquoEuropean Journal of Pharmaceutical Sciences vol 49 no 5 pp864ndash872 2013
[21] J Slane J Vivanco J Meyer H-L Ploeg and M SquireldquoModification of acrylic bone cement with mesoporous silicananoparticles effects on mechanical fatigue and absorptionpropertiesrdquo Journal of the Mechanical Behavior of BiomedicalMaterials vol 29 pp 451ndash461 2014
[22] J E Mathis Z Bi C A Bridges et al ldquoEnhanced visible-lightabsorption of mesoporous TiO
[23] D Sun W Jiang Y Wang et al ldquoSynthesis and enhancedelectromagnetic wave absorption properties of Fe
3O4ZnO
mesoporous spheresrdquoMRS Proceedings vol 1663 2014[24] W Cui Y Li Y Ma and G Yu ldquoResearch on the dehydration
property of one of super absorbent resin on the swill oilrdquoModern Applied Science vol 4 no 10 article no 71 2010
[25] H Ye J-Q Zhao and Y-H Zhang ldquoNovel degradable super-absorbent materials of silicateacrylic-based polymer hybridsrdquoJournal of Applied Polymer Science vol 91 no 2 pp 936ndash9402004
Figure 12 Effect of distilled water quantity on the moisture per-formance of SAP
cross-linking agent only reacted with a spot of free hydroxylgroups on the surface of the resin and remaining cross-linking agents vaporized on heating So the cross-linkingeffect was not stable and the moisture resistance was poorHowever adding a small amount of distilled water cross-linking agent would permeate into the resin in the help ofdistilled water the thickness of surface cross-linking andmoisture resistance were increased after heating treatmentDistilled water at different mass ratios (H
2OC2H5OH =
20 40 60 80) was added in the mixture of 15epoxy chloropropane and absolute ethanol and the moistureresistance was tested When the mass ratio of H
2OC2H5OH
reached 40 the SAP exhibited the best moisture resistanceIf the amount of distilled water kept increasing the resinwould swell seriously adhesion among the particles occurredand the moisture resistance reduced The high cross-linkingdensity coat which formed on the particle surface of the resinby epoxy chloropropane treatment increased the strengthand dispersity of the SAP Combined with the dry surface ofresin particles the moisture resistance of resin was improvedto certain extent In conclusion when the mass ratio ofECHC
2H5OH reached 15 and H
2OC2H5OH reached
40 the properties of the SAP were the best (Figure 12)
362 Effect of Diethylene Glycol (DEG) Dosages on the Proper-ties of SAP Figure 13 shows the spectrum of the SAP beforeand after DEG modification The peak at 1114ndash1120 cmminus1 isstretching vibration peak of the ether groups which indicatedthat diethylene glycol was successfully grafted in SAP
Effect of Diethylene Glycol Dosages on the Water AbsorptionProperties of SAP Table 3 shows the results of the waterabsorption for the different diethylene glycol dosages The
1000
a
b
4000 3500 3000 2500 2000 1500
Wavenumber (cmminus1)
Inte
nsity
Figure 13The IR comparison of the SAP before and after diethyleneglycol modification (a the IR of the SAP before DEG modificationb the IR of the SAP modified by DEG)
0
0
200 400 600
Time (min)800 1000
50
40
30
20
10
The h
ydro
scop
ic ra
te (
)
0
135710
Figure 14 The moisture absorption rate of SAP with differentdosage of diglycol modification
water absorption was tested at different mass ratios of ECHand C
2H5OH (ECHC
2H5OH = 0 1 3 7 10)
Obviously the amount of diethylene glycol dosage had a greateffect on the water absorption The results indicated that theparticles in the resin bonded together performed with poordispersivity when the mass ratio of ECHC
2H5OH exceeded
10 (Figure 14)
Effect of Diethylene Glycol Dosages on the Moisture Resistanceof SAP The resin was modified by the mixture of 2mLdistilled water 5mL anhydrous ethyl alcohol and differentamount of diethylene glycol Results showed that the mois-ture resistance improved with the increasing of the amount
Journal of Polymers 7
Table 4 The optimum reaction conditions
The cellulosemonomerratio
Neutralizationdegree
Oil-waterratio
Reactiontemperature
(∘C)
The ratio ofECHC
2H5OH
The ratio ofDEGC
2H5OH
Water absorptionrate (gg)
Salt waterabsorption rate
(gg)1 10 75 3 1 70 15 5 859 7248
0 200 400 600
Time (min)800 1000
2040
6080
0
5
40
30
35
20
25
10
15
The h
ygro
scop
ic ra
te (
)
Figure 15 The moisture absorption rate of SAP with differentdosage of distilled water
of DEG Compared with the resin treated by ECH themoisture resistance of the SAP treated by DEG exhibitedbetter performance in spite of less gel strength and poorerdryness of resin surface Once the amount of DEG was morethan 7 the adhesion would happen among the particles ofresin And it was difficult to granulate after drying
Effect of Distilled Water Quantity on the Moisture Perfor-mance of SAP When distilled water at different mass ratios(H2OC2H5OH = 20 40 60 80) was added the
moisture resistance of the resin which was processed by 5DEG was measured The addition of distilled water had littleinfluence on the treatment of DEG in respect of the factthat the DEG is a hydrophilic agent with great property ofpenetrability it can infiltrate easily without water (Figure 15)
The humidity resistance of the resin improved with theincreasing amount of DEG The water absorption efficiencyreduced and the impact was lower than the resin processedby ECH When the amount of DEG exceeded 10 theparticles among the resin adhered seriously Although themoisture resistance of the resin treated by DEG was betterthan that treated by ECH the gel strength and dispersity wereinferior to it
37 The Optimum Reaction Conditions The optimum reac-tion conditions are as shown in Table 4
4 Conclusions
In this study the superabsorbent polymer has been syn-thesized through inverse suspension polymerization The
absorption experiments for water and salt water showedthat the operating conditions such as monomer dosagesneutralization degree oil-water ratio temperature and thecross-linking agent had great effects on the water absorp-tion The optimum reaction conditions were as follows thecellulose monomer ratio 1 10 neutralization degree 75oil-water ratio 3 1 and reaction temperature 70∘C Thewater and salt water absorption rate can reach as high as859 gg and 7248 gg respectively Moreover the moistureresistance of the resin treated by ECHandDEGwas improvedsignificantly The moisture resistance showed the best whenthe addition of ECH was 15 and it increased with theincreasing amount of DEG but when the dosage of DEGexceeded 5 the particles among the resin adhered seriously
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
This work was supported by the Scientific Research ProgramofHubei Provincial Department of Education (B2015321) andthe Science Research Fund ofWuhan Institute of Technology
References
[1] H Kono and S Fujita ldquoBiodegradable superabsorbent hydro-gels derived from cellulose by esterification crosslinking with1234-butanetetracarboxylic dianhydriderdquo Carbohydrate Poly-mers vol 87 no 4 pp 2582ndash2588 2012
[2] R Ding and K Gong ldquoSuper-absorbent resin preparation uti-lizing spent mushroom substratesrdquo Journal of Applied PolymerScience vol 130 no 2 pp 1098ndash1103 2013
[3] D Wang Z-Q Song and S-B Shang ldquoCharacterizationand biodegradability of amphoteric superabsorbent polymersrdquoJournal of Applied Polymer Science vol 107 no 6 pp 4116ndash41202008
[4] L A Gugliemelli M OWeaver and C R Russell Salt-resistantthickeners comprising base-saponified starch-polyacrylonitrilegraft copolymers US Patent 3425971[P] 1969-2-4
[5] K Kabir H Mirzadeh M J Zohuriaan-Mehr and M DalirildquoChitosan-modified nanoclay-poly(AMPS) nanocompositehydrogels with improved gel strengthrdquo Polymer Internationalvol 58 no 11 pp 1252ndash1259 2009
[6] D Shen T Wang Y Chen M Wang and G Jiang ldquoEffect ofinternal curing with super absorbent polymers on the relativehumidity of early-age concreterdquo Construction and BuildingMaterials vol 99 pp 246ndash253 2015
[7] Y GHan P L Yang Y P Luo SM Ren L X Zhang and L XuldquoPorosity change model for watered super absorbent polymer-treated soilrdquo Environmental Earth Sciences vol 61 no 6 pp1197ndash1205 2010
8 Journal of Polymers
[8] L Zhou Y Wang Z Liu and Q Huang ldquoCharacteristics ofequilibrium kinetics studies for adsorption of Hg(II) Cu(II)and Ni(II) ions by thiourea-modifiedmagnetic chitosan micro-spheresrdquo Journal of Hazardous Materials vol 161 no 2-3 pp995ndash1002 2009
[9] C Chang B Duan J Cai and L Zhang ldquoSuperabsorbenthydrogels based on cellulose for smart swelling and controllabledeliveryrdquo European Polymer Journal vol 46 no 1 pp 92ndash1002010
[10] Y Bulut G Akcay D Elma and I E Serhatli ldquoSynthesis of clay-based superabsorbent composite and its sorption capabilityrdquoJournal of Hazardous Materials vol 171 no 1ndash3 pp 717ndash7232009
[11] J Zhang L Wang and A Wang ldquoPreparation and swellingbehavior of fast-swelling superabsorbent hydrogels based onstarch-g-poly(acrylic acid-co-sodium acrylate)rdquoMacromolecu-lar Materials and Engineering vol 291 no 6 pp 612ndash620 2006
[12] S Changchaivong and S Khaodhiar ldquoAdsorption of naph-thalene and phenanthrene on dodecylpyridinium-modifiedbentoniterdquoApplied Clay Science vol 43 no 3 pp 317ndash321 2009
[13] G R Mahdavinia A Pourjavadi and M J Zohuriaan-MehrldquoA convenient one-step preparation of chitosan-poly(sodiumacrylate-co-acrylamide) hydrogel hybrids with super-swellingpropertiesrdquo Journal of Applied Polymer Science vol 99 no 4pp 1615ndash1619 2006
[14] Y Zhou S Fu L Zhang and H Zhan ldquoSuperabsorbentnanocomposite hydrogels made of carboxylated cellulosenanofibrils and CMC-g-p(AA-co-AM)rdquo Carbohydrate Poly-mers vol 97 no 2 pp 429ndash435 2013
[15] H A EssawyM BM Ghazy F A El-Hai andM FMohamedldquoSuperabsorbent hydrogels via graft polymerization of acrylicacid from chitosan-cellulose hybrid and their potential incontrolled release of soil nutrientsrdquo International Journal ofBiological Macromolecules vol 89 pp 144ndash151 2016
[16] T Fekete J Borsa E Takacs and L Wojnarovits ldquoSynthesisof cellulose-based superabsorbent hydrogels by high-energyirradiation in the presence of crosslinking agentrdquo RadiationPhysics and Chemistry vol 118 pp 114ndash119 2014
[17] F F Montesano A Parente P Santamaria A Sannino and FSerio ldquoBiodegradable superabsorbent hydrogel increaseswaterretention properties of growing media and plant growthrdquoAgriculture and Agricultural Science Procedia vol 4 pp 451ndash458 2015
[18] S Mohammadi-Khoo P N Moghadam A R Fareghi andN Movagharnezhad ldquoSynthesis of a cellulose-based hydrogelnetwork characterization and study of urea fertilizer slowreleaserdquo Journal of Applied Polymer Science vol 133 no 5Article ID 42935 2016
[19] M Bakass J P Bellat A Mokhlisse and G Bertrand ldquoTheadsorption of water vapor on super absorbent product at lowtemperatures and lowmassrdquo Journal of Applied Polymer Sciencevol 100 no 2 pp 1450ndash1456 2006
[20] Y Zhang H Wang C Gao X Li and L Li ldquoHighly orderedmesoporous carbon nanomatrix as a new approach to improvethe oral absorption of the water-insoluble drug simvastatinrdquoEuropean Journal of Pharmaceutical Sciences vol 49 no 5 pp864ndash872 2013
[21] J Slane J Vivanco J Meyer H-L Ploeg and M SquireldquoModification of acrylic bone cement with mesoporous silicananoparticles effects on mechanical fatigue and absorptionpropertiesrdquo Journal of the Mechanical Behavior of BiomedicalMaterials vol 29 pp 451ndash461 2014
[22] J E Mathis Z Bi C A Bridges et al ldquoEnhanced visible-lightabsorption of mesoporous TiO
[23] D Sun W Jiang Y Wang et al ldquoSynthesis and enhancedelectromagnetic wave absorption properties of Fe
3O4ZnO
mesoporous spheresrdquoMRS Proceedings vol 1663 2014[24] W Cui Y Li Y Ma and G Yu ldquoResearch on the dehydration
property of one of super absorbent resin on the swill oilrdquoModern Applied Science vol 4 no 10 article no 71 2010
[25] H Ye J-Q Zhao and Y-H Zhang ldquoNovel degradable super-absorbent materials of silicateacrylic-based polymer hybridsrdquoJournal of Applied Polymer Science vol 91 no 2 pp 936ndash9402004
Figure 15 The moisture absorption rate of SAP with differentdosage of distilled water
of DEG Compared with the resin treated by ECH themoisture resistance of the SAP treated by DEG exhibitedbetter performance in spite of less gel strength and poorerdryness of resin surface Once the amount of DEG was morethan 7 the adhesion would happen among the particles ofresin And it was difficult to granulate after drying
Effect of Distilled Water Quantity on the Moisture Perfor-mance of SAP When distilled water at different mass ratios(H2OC2H5OH = 20 40 60 80) was added the
moisture resistance of the resin which was processed by 5DEG was measured The addition of distilled water had littleinfluence on the treatment of DEG in respect of the factthat the DEG is a hydrophilic agent with great property ofpenetrability it can infiltrate easily without water (Figure 15)
The humidity resistance of the resin improved with theincreasing amount of DEG The water absorption efficiencyreduced and the impact was lower than the resin processedby ECH When the amount of DEG exceeded 10 theparticles among the resin adhered seriously Although themoisture resistance of the resin treated by DEG was betterthan that treated by ECH the gel strength and dispersity wereinferior to it
37 The Optimum Reaction Conditions The optimum reac-tion conditions are as shown in Table 4
4 Conclusions
In this study the superabsorbent polymer has been syn-thesized through inverse suspension polymerization The
absorption experiments for water and salt water showedthat the operating conditions such as monomer dosagesneutralization degree oil-water ratio temperature and thecross-linking agent had great effects on the water absorp-tion The optimum reaction conditions were as follows thecellulose monomer ratio 1 10 neutralization degree 75oil-water ratio 3 1 and reaction temperature 70∘C Thewater and salt water absorption rate can reach as high as859 gg and 7248 gg respectively Moreover the moistureresistance of the resin treated by ECHandDEGwas improvedsignificantly The moisture resistance showed the best whenthe addition of ECH was 15 and it increased with theincreasing amount of DEG but when the dosage of DEGexceeded 5 the particles among the resin adhered seriously
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
This work was supported by the Scientific Research ProgramofHubei Provincial Department of Education (B2015321) andthe Science Research Fund ofWuhan Institute of Technology
References
[1] H Kono and S Fujita ldquoBiodegradable superabsorbent hydro-gels derived from cellulose by esterification crosslinking with1234-butanetetracarboxylic dianhydriderdquo Carbohydrate Poly-mers vol 87 no 4 pp 2582ndash2588 2012
[2] R Ding and K Gong ldquoSuper-absorbent resin preparation uti-lizing spent mushroom substratesrdquo Journal of Applied PolymerScience vol 130 no 2 pp 1098ndash1103 2013
[3] D Wang Z-Q Song and S-B Shang ldquoCharacterizationand biodegradability of amphoteric superabsorbent polymersrdquoJournal of Applied Polymer Science vol 107 no 6 pp 4116ndash41202008
[4] L A Gugliemelli M OWeaver and C R Russell Salt-resistantthickeners comprising base-saponified starch-polyacrylonitrilegraft copolymers US Patent 3425971[P] 1969-2-4
[5] K Kabir H Mirzadeh M J Zohuriaan-Mehr and M DalirildquoChitosan-modified nanoclay-poly(AMPS) nanocompositehydrogels with improved gel strengthrdquo Polymer Internationalvol 58 no 11 pp 1252ndash1259 2009
[6] D Shen T Wang Y Chen M Wang and G Jiang ldquoEffect ofinternal curing with super absorbent polymers on the relativehumidity of early-age concreterdquo Construction and BuildingMaterials vol 99 pp 246ndash253 2015
[7] Y GHan P L Yang Y P Luo SM Ren L X Zhang and L XuldquoPorosity change model for watered super absorbent polymer-treated soilrdquo Environmental Earth Sciences vol 61 no 6 pp1197ndash1205 2010
8 Journal of Polymers
[8] L Zhou Y Wang Z Liu and Q Huang ldquoCharacteristics ofequilibrium kinetics studies for adsorption of Hg(II) Cu(II)and Ni(II) ions by thiourea-modifiedmagnetic chitosan micro-spheresrdquo Journal of Hazardous Materials vol 161 no 2-3 pp995ndash1002 2009
[9] C Chang B Duan J Cai and L Zhang ldquoSuperabsorbenthydrogels based on cellulose for smart swelling and controllabledeliveryrdquo European Polymer Journal vol 46 no 1 pp 92ndash1002010
[10] Y Bulut G Akcay D Elma and I E Serhatli ldquoSynthesis of clay-based superabsorbent composite and its sorption capabilityrdquoJournal of Hazardous Materials vol 171 no 1ndash3 pp 717ndash7232009
[11] J Zhang L Wang and A Wang ldquoPreparation and swellingbehavior of fast-swelling superabsorbent hydrogels based onstarch-g-poly(acrylic acid-co-sodium acrylate)rdquoMacromolecu-lar Materials and Engineering vol 291 no 6 pp 612ndash620 2006
[12] S Changchaivong and S Khaodhiar ldquoAdsorption of naph-thalene and phenanthrene on dodecylpyridinium-modifiedbentoniterdquoApplied Clay Science vol 43 no 3 pp 317ndash321 2009
[13] G R Mahdavinia A Pourjavadi and M J Zohuriaan-MehrldquoA convenient one-step preparation of chitosan-poly(sodiumacrylate-co-acrylamide) hydrogel hybrids with super-swellingpropertiesrdquo Journal of Applied Polymer Science vol 99 no 4pp 1615ndash1619 2006
[14] Y Zhou S Fu L Zhang and H Zhan ldquoSuperabsorbentnanocomposite hydrogels made of carboxylated cellulosenanofibrils and CMC-g-p(AA-co-AM)rdquo Carbohydrate Poly-mers vol 97 no 2 pp 429ndash435 2013
[15] H A EssawyM BM Ghazy F A El-Hai andM FMohamedldquoSuperabsorbent hydrogels via graft polymerization of acrylicacid from chitosan-cellulose hybrid and their potential incontrolled release of soil nutrientsrdquo International Journal ofBiological Macromolecules vol 89 pp 144ndash151 2016
[16] T Fekete J Borsa E Takacs and L Wojnarovits ldquoSynthesisof cellulose-based superabsorbent hydrogels by high-energyirradiation in the presence of crosslinking agentrdquo RadiationPhysics and Chemistry vol 118 pp 114ndash119 2014
[17] F F Montesano A Parente P Santamaria A Sannino and FSerio ldquoBiodegradable superabsorbent hydrogel increaseswaterretention properties of growing media and plant growthrdquoAgriculture and Agricultural Science Procedia vol 4 pp 451ndash458 2015
[18] S Mohammadi-Khoo P N Moghadam A R Fareghi andN Movagharnezhad ldquoSynthesis of a cellulose-based hydrogelnetwork characterization and study of urea fertilizer slowreleaserdquo Journal of Applied Polymer Science vol 133 no 5Article ID 42935 2016
[19] M Bakass J P Bellat A Mokhlisse and G Bertrand ldquoTheadsorption of water vapor on super absorbent product at lowtemperatures and lowmassrdquo Journal of Applied Polymer Sciencevol 100 no 2 pp 1450ndash1456 2006
[20] Y Zhang H Wang C Gao X Li and L Li ldquoHighly orderedmesoporous carbon nanomatrix as a new approach to improvethe oral absorption of the water-insoluble drug simvastatinrdquoEuropean Journal of Pharmaceutical Sciences vol 49 no 5 pp864ndash872 2013
[21] J Slane J Vivanco J Meyer H-L Ploeg and M SquireldquoModification of acrylic bone cement with mesoporous silicananoparticles effects on mechanical fatigue and absorptionpropertiesrdquo Journal of the Mechanical Behavior of BiomedicalMaterials vol 29 pp 451ndash461 2014
[22] J E Mathis Z Bi C A Bridges et al ldquoEnhanced visible-lightabsorption of mesoporous TiO
[23] D Sun W Jiang Y Wang et al ldquoSynthesis and enhancedelectromagnetic wave absorption properties of Fe
3O4ZnO
mesoporous spheresrdquoMRS Proceedings vol 1663 2014[24] W Cui Y Li Y Ma and G Yu ldquoResearch on the dehydration
property of one of super absorbent resin on the swill oilrdquoModern Applied Science vol 4 no 10 article no 71 2010
[25] H Ye J-Q Zhao and Y-H Zhang ldquoNovel degradable super-absorbent materials of silicateacrylic-based polymer hybridsrdquoJournal of Applied Polymer Science vol 91 no 2 pp 936ndash9402004
[8] L Zhou Y Wang Z Liu and Q Huang ldquoCharacteristics ofequilibrium kinetics studies for adsorption of Hg(II) Cu(II)and Ni(II) ions by thiourea-modifiedmagnetic chitosan micro-spheresrdquo Journal of Hazardous Materials vol 161 no 2-3 pp995ndash1002 2009
[9] C Chang B Duan J Cai and L Zhang ldquoSuperabsorbenthydrogels based on cellulose for smart swelling and controllabledeliveryrdquo European Polymer Journal vol 46 no 1 pp 92ndash1002010
[10] Y Bulut G Akcay D Elma and I E Serhatli ldquoSynthesis of clay-based superabsorbent composite and its sorption capabilityrdquoJournal of Hazardous Materials vol 171 no 1ndash3 pp 717ndash7232009
[11] J Zhang L Wang and A Wang ldquoPreparation and swellingbehavior of fast-swelling superabsorbent hydrogels based onstarch-g-poly(acrylic acid-co-sodium acrylate)rdquoMacromolecu-lar Materials and Engineering vol 291 no 6 pp 612ndash620 2006
[12] S Changchaivong and S Khaodhiar ldquoAdsorption of naph-thalene and phenanthrene on dodecylpyridinium-modifiedbentoniterdquoApplied Clay Science vol 43 no 3 pp 317ndash321 2009
[13] G R Mahdavinia A Pourjavadi and M J Zohuriaan-MehrldquoA convenient one-step preparation of chitosan-poly(sodiumacrylate-co-acrylamide) hydrogel hybrids with super-swellingpropertiesrdquo Journal of Applied Polymer Science vol 99 no 4pp 1615ndash1619 2006
[14] Y Zhou S Fu L Zhang and H Zhan ldquoSuperabsorbentnanocomposite hydrogels made of carboxylated cellulosenanofibrils and CMC-g-p(AA-co-AM)rdquo Carbohydrate Poly-mers vol 97 no 2 pp 429ndash435 2013
[15] H A EssawyM BM Ghazy F A El-Hai andM FMohamedldquoSuperabsorbent hydrogels via graft polymerization of acrylicacid from chitosan-cellulose hybrid and their potential incontrolled release of soil nutrientsrdquo International Journal ofBiological Macromolecules vol 89 pp 144ndash151 2016
[16] T Fekete J Borsa E Takacs and L Wojnarovits ldquoSynthesisof cellulose-based superabsorbent hydrogels by high-energyirradiation in the presence of crosslinking agentrdquo RadiationPhysics and Chemistry vol 118 pp 114ndash119 2014
[17] F F Montesano A Parente P Santamaria A Sannino and FSerio ldquoBiodegradable superabsorbent hydrogel increaseswaterretention properties of growing media and plant growthrdquoAgriculture and Agricultural Science Procedia vol 4 pp 451ndash458 2015
[18] S Mohammadi-Khoo P N Moghadam A R Fareghi andN Movagharnezhad ldquoSynthesis of a cellulose-based hydrogelnetwork characterization and study of urea fertilizer slowreleaserdquo Journal of Applied Polymer Science vol 133 no 5Article ID 42935 2016
[19] M Bakass J P Bellat A Mokhlisse and G Bertrand ldquoTheadsorption of water vapor on super absorbent product at lowtemperatures and lowmassrdquo Journal of Applied Polymer Sciencevol 100 no 2 pp 1450ndash1456 2006
[20] Y Zhang H Wang C Gao X Li and L Li ldquoHighly orderedmesoporous carbon nanomatrix as a new approach to improvethe oral absorption of the water-insoluble drug simvastatinrdquoEuropean Journal of Pharmaceutical Sciences vol 49 no 5 pp864ndash872 2013
[21] J Slane J Vivanco J Meyer H-L Ploeg and M SquireldquoModification of acrylic bone cement with mesoporous silicananoparticles effects on mechanical fatigue and absorptionpropertiesrdquo Journal of the Mechanical Behavior of BiomedicalMaterials vol 29 pp 451ndash461 2014
[22] J E Mathis Z Bi C A Bridges et al ldquoEnhanced visible-lightabsorption of mesoporous TiO
[23] D Sun W Jiang Y Wang et al ldquoSynthesis and enhancedelectromagnetic wave absorption properties of Fe
3O4ZnO
mesoporous spheresrdquoMRS Proceedings vol 1663 2014[24] W Cui Y Li Y Ma and G Yu ldquoResearch on the dehydration
property of one of super absorbent resin on the swill oilrdquoModern Applied Science vol 4 no 10 article no 71 2010
[25] H Ye J-Q Zhao and Y-H Zhang ldquoNovel degradable super-absorbent materials of silicateacrylic-based polymer hybridsrdquoJournal of Applied Polymer Science vol 91 no 2 pp 936ndash9402004
