Champion Industries, Vitthal Udyognagar 388121, IndiaInstitute of Science & Technology for Advanced Studies & Research, Vallabh Vidyanagar 388120, IndiaDepartment of Chemistry, Sardar Patel University, Vallabh Vidyanagar 388120, India
r t i c l e i n f o
rticle history:eceived 10 August 2009eceived in revised form 16 October 2009ccepted 28 November 2009
eywords:olyurethaneispersionsatty acid
a b s t r a c t
The higher molecular weight fatty acid modified polyurethane–urea dispersions (PUDs) were preparedwith effective utilization of fatty acid and ionic emulsifier. The PUDs were prepared using oligomerof linoleic fatty acid, dimethylol propionic acid (DMPA), linear polyester diol, isophorone diisocyanate(IPDI), triethylamine (TEA) and ethylenediamine (EDA) by prepolymer mixing method. Resultant PUDshad so-called controlled branched polymer structures. To incorporate fatty acid residues in the backboneof the polyurethane two types of oligomers were used which were synthesized by esterifying linoleicacid and phthalic anhydride (PA) with different monomers having different hydroxyl functionality i.e.trimethylol propane (TMP), pentaerythritol and neopentyl glycol (NPG). The oligomers were mixed with
uto-oxidationontrolled branch polymer structure
linear polyester diol in different proportions and used as polyol part in prepolymer for PUDs. Variouscompositional variations such as type of oligomer, content of oligomer and ionic emulsifier were studiedfor stability and compatibility with water. The PUDs were also examined by FTIR, AFM, GPC, particle sizeanalyzer, viscometer, TGA, DMA and tensile tester to analyze structures and properties. Chemical, waterand corrosion resistances of the dried films were also evaluated to study the effect of oligomer content inmodified PUDs. These properties are found to be significantly affected by the content and type of oligomer
the
as well as ionic content in
. Introduction
Auto-oxidizable resin systems represent the oldest family forurface coatings and still are in wide use. The highest performinglasses are those that are urethane modified. Recent advances inuto-oxidizable urethane resins have primarily been in waterborneechnologies and applications in context to the recent and upcom-ng demand for VOC compliant eco-friendly coating solutions.ralkyds adapted to waterborne application and new polyurethaneispersions with drying oil modifications are breathing new life
nto an established chemistry. Aqueous dispersion of polyurethanes achieved by having acid residues on the backbone and quat-rnizing these groups by tertiary amines render ionic groups onhe polymer backbone, which imparts the water dispersibility. The
ost frequently used monomer to incorporate hydrophilic groups dimethylol propionic acid (DMPA).
Polyurethane dispersion is generally prepared by prepolymerixing process [1–8] in which isocyanate terminated prepoly-
mer is dispersed in water and chain extended with difunctionalor multifunctional amine through very fast reaction between iso-cyanate groups and amines. At the same time phase reversal takesplace.
PUDs contain a hard segment and soft segment in polymerbackbone with polymeric diols as soft segments and urethaneand urea groups as hard segments [9,10]. Proposed oxidativePolyurethane–urea dispersions can be prepared by replacing softsegment with polyhydric precursors containing double bonds suchas monoglyceride of the drying oils, transesterified precursors ofdrying oil and oligomer of fatty acids [11–16]. However, use ofthese oligomers as such apt to easy gelation and/or separation ofdispersion masses during chain extension. This may be due to thehigh degree of branching during chain extension or poor seed for-mation during phase reversal process. Some of the work had alsobeen reported, in which chain extension was omitted to overcomethis deficiency but it leads to low molecular weight polymer [17].Therefore, they were often mixed with linear diol to control the
functionality of the prepolymer. However, to achieve stable disper-sion with smaller particle size, these routes utilized higher amountof internal emulsifier than those for linear polyester diols. Andbecause of higher ionic content polymer film has high water sensi-tivity. In this regard, the studies are meager on controlled branching
f the polymer backbone of the PUD that can be effectively utilizedor the water dispersibility.
In the present work, linoleic acid modified PUDs were syn-hesized using prepolymer mixing process with variation in typef oligomer, amount of oligomer (therefore % fatty acid content)nd DMPA content. Two types of oligomers were used in theresent study; first one was synthesized by esterifying linoleic acid,hthalic anhydride, TMP and pentaerythritol while second one wasrom linoleic acid, phthalic anhydride, TMP and NPG. The study wasocused on behavior of dispersion mass upon the chain extension inerms of stability and average particle size. It is necessary to achieveontrolled branch polymer structure during chain extension stepo yield stable PUDs. Therefore, to study the effect of amount ofligomer on degree of branching in the polymer backbone, dif-erent combinations of oligomers and linear polyester diols weresed to prepare PUDs and optimized for effective branching of theolymer backbone which is so-called controlled branch polymertructure. Film formation of stable PUD was studied by atomic forceicroscopy (AFM). Then performance properties like water, chem-
cal and corrosion resistance and tensile properties of the castedlms of the stable PUDs were evaluated to investigate the effectf oligomer and also % fatty acid content in the composition. Alsohe same was studied by thermo gravimetric analysis (TGA) andynamic mechanical analysis (DMA) of the dried films.
. Materials and methods
.1. Materials
In the present study poly-neopentylglycol adipate (PD) (OHumber = 110 mg KOH/g) was used as linear polyester diol, whichas prepared by esterifying neopentyl glycol and adipic acid. Itas dried and degassed under vacuum at 80 ◦C for 8 h before use.ther materials viz. linoleic acid (LA) (N.R. Chemicals, Mumbai,
Fig. 1. Schematic diagram of prepara
Color (Gardner scale) 3 3Acid value (mg KOH/g) 4.1 4.5Average functionality 1.98 1.79
India), neopentyl glycol (NPG) (Chiti Chem, Vadodara, India), pen-taerythritol, phthalic anhydride (PA), trimethylol propane (TMP),triethylamine (TEA), 1,2-ethylenediamine (EDA), isophorone diiso-cyanate (IPDI) (Degussa, USA), 1-methyl-2-pyrrolidone (NMP)(Merk, India), and 2,2-bis(hydroxymethyl)propionic acid (DMPA)(Perstrop India Pvt Ltd., Vapi, India) were used as received. Deion-ized water (DIW) was procured from SICART, Vallabh Vidyanagar,India.
2.2. Methods
2.2.1. Preparation of fatty acid based oligomers (PE)Linoleic acid based oligomers were prepared by esterification of
linoleic fatty acid and phthalic anhydride with TMP and neopentylglycol or pentaerythritol in the presence of dibutyl tin dilaurate(DBTDL) as esterification catalyst as per the reported procedure
tion of fatty acid modified PUD.
A. Patel et al. / Progress in Organic Coatings 67 (2010) 255–263 257
er Stru
[pwT
2
wtcp8bt
TltptsTp
22i
Fig. 2. Controlled Branched Polym
18] until the acid number was below 5 mg of KOH/g. Com-osition and physico-chemical properties of different oligomersith different hydroxyl functional monomers are presented in
able 1.
.2.2. Preparation of PUDsPUDs were synthesized in round bottom glass reactor equipped
ith a mechanical stirrer, a thermometer, a reflux condenser, aemperature controller, and a nitrogen inlet using prepolymer pro-ess as described in literature [19]. The isocyanate terminatedrepolymer was prepared by reacting IPDI, PE, PD and DMPA at0 ◦C using NMP as solvent until the NCO content as determinedy the di-n-butylamine back-titration method [20] reached to aheoretical value.
The isocyanate terminated prepolymer is then neutralized byEA to 90% neutralization at 60 ◦C and then cooled to 30 ◦C fol-owed by dispersion in water and chain extension by EDA as perhe reported process [20]. Water-based PUD was formed throughhase inversion process. The schematic illustration of the prepara-ion of the PUD is given in Fig. 1. The controlled branched polymertructure of resulting polymer is represented schematically in Fig. 2.he compositions of fatty acid modified polyurethane dispersions
repared are given in Table 2.
.2.3. Characterization of intermediates and PUDs
.2.3.1. Physical properties. The PUDs were characterized for var-ous physical characteristics viz. viscosity, color, particle size,
cture of Fatty acid Modified PUD.
compatibility with water and stability. The viscosity of dispersionswas determined by Brookfield viscometer (ASTM D 2196) using RVTModel (spindle 6 at 100 rpm). Particle size distributions of PUDswere determined by dynamic light scattering using a Malvern 1000particle size analyzer. Color of the dispersion masses were checkedon gardener scale. As the present work deals with the developmentof water-based resin, the dispersions prepared must be compatiblewith water even at high dilution; therefore prepared PUDs wereexamined for water compatibility test. In the test, the sample wastaken in 100 ml glass cylinder and water (equal amount) was added.After addition the material was mixed thoroughly and observed formiscibility. The storage stability of the PUDs was checked by stor-ing the sample for 1 month at 50 ◦C. Any negative change in theappearance like phase separation was observed and reported. Theresults are reported in Table 4.
2.2.3.2. Performance properties. The dried PUD films were also eval-uated for their performance properties such as water uptake,solvent resistance and corrosion resistance. Water-based dri-ers were used to induce oxidative polymerization of the filmsto be used for performance properties. The water uptakeof the films was measured by immersing preweighed films
(40 mm × 20 mm × 0.10 mm in size) in deionized water for 5 daysat room temperature. After each 24 h the film was taken out andsurface water was wiped from the film surface using tissue paperfollowed by immediate weighing of the swollen film. The wateruptake (WU) was expressed as the weight percentage of water in
258 A. Patel et al. / Progress in Organic Coatings 67 (2010) 255–263
of 2 ◦C/min and a testing frequency of 1 Hz. Samples are dumb-
A4 20,543 66,055 3.22
he swollen film expressed as
U (%) =[
Ws − WdWd
]× 100%
here Ws is the weight of the swollen film and Wd is the weightf the original dry film.
Solvent resistance was determined on PUD films applied on-1000 phosphate-treated steel panels. Coatings were subjectedo a 10-min spot test [21] by placing a 25-mm diameter piece oflter paper on the coating and adding 10 drops of solvent. The sol-ent was covered with a watch glass to prevent evaporation. After0 min, coating was examined for softening and loss of gloss. Theorrosion resistance was checked by salt spray test according to
STM B 117. The test panels were scribed diagonally and test wasun for 100 h. Rating of 1–5 was used to express the solvent resis-ance and corrosion resistance where 1 being the worst and 5 beinghe best.
of ionic monomer of total weight solid of polymer.
2.2.3.3. Instrumental analysis. Different intermediates and film offinal PUDs were analyzed for Fourier transform infrared (FTIR) spec-troscopy using Spectrum GX FTIR spectrophotometer (PerkinElmer,USA) in the mid operating range of 4000–400 cm−1. The molec-ular weights of final PUDs were determined by gel permeationchromatography (GPC) performed on instrument Series 2000(PerkinElmer, USA). The films of PUDs were casted and dried undervacuum at 60 ◦C. They were dissolved in THF and the solutionswere pumped through the column at a flow rate of 0.1 �l min−1.The cured casted films of the dispersions were tested for ten-sile properties using a Lloyd LR10K tensile tester. Films werecasted to give around 60-�m dry film thickness and matured for7 days at room temperature. The test specimens of the dimensions200 mm × 10 mm × 0.06 mm were cut from the dried films andpulled at cross-head speed of 300 mm min−1 to determine initialYoung’s modulus, tensile strength and the elongation at break. Toevaluate hydrophilicity of the PUD films, the contact angle formedbetween water drops and the surface of the sample was measuredusing contact angle measuring system G-10 (KRUSS). The drop ofwater was mounted on the surface to be tested with a micro-syringe and contact angle was measured from the view of waterdrops as observed on monitor. Results are mean value of threemeasurements on different parts of the film. Dynamic mechani-cal analysis was carried out on a DMA apparatus at a heating rate
bell shape (3.8 mm × 10 mm × 5 mm) and are measured in a singlecantilever mode. Surface morphology was studied by atomic forcemicroscopy using instrument Model DICP2 (Veeco-Asia, Singapore)before and after drying of the casted film.
of oligomer PE2.
A. Patel et al. / Progress in Organic Coatings 67 (2010) 255–263 259
prepo
3
3
AImTCssambbtm
tiaml
Fig. 4. The FTIR spectra of
. Result and discussion
.1. FTIR spectroscopy
The FTIR spectra of oligomer PE2, prepolymer of composition4 and final dispersion of composition A4 are shown in Figs. 3–5.
n the spectra of PE2, the characteristic strong band at 3528 cm−1
ay be attributed to O–H stretching vibrations of hydroxyl group.he small shoulder at 3008 cm−1 corresponds to unsaturated–H stretching of alkene i.e. unsaturation of linoleic acid. Thetrong absorption at 2926 cm−1 and 2855 cm−1 corresponds to C–Htretching of alkyl group. The strong band at 1738 cm−1 may bettributed to carbonyl (C O) stretching of ester linkages in the poly-er. The peak at 1464 cm−1 is due to C–H bending of –CH3 and the
roadening in the peak due to –C C– group. The peak due to –CH3ending exists at 1385 cm−1. The peak at 1122 cm−1 correspondso C–O–C stretching of ester, and the peak at 741 cm−1 is due to
ultiple CH2 split from (–CH2–)n.In FTIR spectra of prepolymer of composition A4, strong absorp-
−1
ion at 2264 cm reveals the presence of free isocyanate (free NCO)n the prepolymer. The lesser intensity of the bands at 3312 cm−1
s compared to those in PE2 indicates the reaction of free pri-ary hydroxyl with isocyanate group of IPDI to generate urethane
inkages in the prepolymer. The peaks at 1537 cm−1 are due to
Fig. 5. The FTIR spectra of final p
lymer of composition A4.
stretching vibration of –CONH– group representing the formationof urethane linkage.
In FTIR spectra of PUD of composition A4 an absorption bandis observed for the N–H stretching at 3376 cm−1, aliphatic C–Hstretching peak at 2878 cm−1 and 2958 cm−1 belongs to –CH2–and –CH3– groups. The carbonyl (C O) stretching at 1731 cm−1,N–H bending vibration (stretching vibration of C–N and bend-ing vibration of N–H) at 1657 cm−1and C–O–C stretching at1000–1150 cm−1. These vibrations are strong evidences for theformation of PU. The peak at 1458 cm−1 is due to methyl and methy-lene groups of all polyesters.
3.2. Effect of the oligomer content
Composition of linoleic acid modified oligomers and PUDs fromthem is given in Tables 1 and 2, respectively. In compositions A1and B1, PE2 and PE1 were used as a sole polyol segment in theprepolymer, respectively. Both the batches were not succeeded(Table 4). The composition A1 showed poor stability (immediate
separation after dispersion) and composition B1 got gelled duringchain extension. This is due to the high functionality of oligomersthat yields highly branched prepolymer which in turn results inuncontrolled polymer structure upon further chain extension andget gelled or separated. The same was also concluded by Russiello
olymer of composition A4.
260 A. Patel et al. / Progress in Organic Coatings 67 (2010) 255–263
Table 4Physico-chemical properties of PUDs.
Composition Oligomer content (wt%) Particle size (nm) Viscosity (centipoise) at 25 ◦C Compatibility with water Stability Color
A1 54.01 a a a S 3A2a 36.75 650 60 C S 3A2 37.82 120 150 C NS 3A3 45.90 110 155 C NS 3A4 53.91 114 147 C NS 3B1 54.88 b b b b b
B2 38.13 110 83 C NS 3B3 45.80 – 70 C S 3
b b b b b
S
[clrpifomoBwigBsAoA5tbBwibd[d
opb
B4 53.6
= separation; NS = no separation; C = compatible.a No data.b Gelled.
22] that higher functionality of the prepolymer prepared usingrosslinked polyester polyol or using short chain triol or tetrol withinear functional polydiol forms very large micelles during phaseeversal process which ultimately reduces the stability of the dis-ersion or gets separated immediately in extreme cases. Therefore,
n other compositions the oligomers had been mixed with PD in dif-erent ratios in increasing PE content and hence increasing contentf linoleic acid residues, i.e. around 20%, 24% and 28% of polymerass. However, NCO/OH mole ratio was kept constant. From set
f the PUDs based on PE1 with 8% ionic content, only composition2 with 38% oligomer (20% linoleic acid) exhibited good stabilityith average particle size of 110 nm. This was found to be the max-
mum limit for fatty acid inclusion and above this, compositionselled (composition B4) or got separated on storage (composition3). On the other hand for set of PUDs based on oligomer PE2howed encouraging results in terms of oligomer incorporation.ll the PUDs based on PE2 were successful and maximum 54% ofligomer (28% linoleic acid) could be included i.e. for composition4. For the compositions A2, A3 and A4 the ionic contents were 5.2,.3 and 5.5, respectively. Below this limit, dispersion of coarser par-icle size was resulted with unstable mass on storage as revealedy poor stability of composition A2a. The stability of compositions2, A2, A3 and A4 can be attributed to substitution of part of the PEith PD which being linear polymeric diol, controls the functional-
ty of the prepolymer which yield stable dispersions with controlledranched polymer backbone upon chain extension. This is in accor-ance with the work by the Schafheutle et al. [23] and Gündüz et al.24,25], who prepared PUDs with effective use of crosslinked polyol
iluted with the polymeric diol in appropriate amount.
One of the reasons for these distinguished results for PUDs basedn PE1 and PE2 lies in the functionality of the monomers used torepare these oligomers. Trifunctionality of the TMP used in PE2 isalanced by monofunctional linoleic acid that ultimately controls
Fig. 6. AFM images of PUD films before dr
the functionality of the oligomer. Combination of these oligomerswith difunctional PD further limit the functionality of the prepoly-mer up to the level that can be effectively used in the preparationof controlled branched polymer to yield polyurethane dispersionwithout any gelation or separation. While pentaerythritol used inPE1 is tetrafunctional hence its functionality in oligomer cannot belimited effectively to produce stable dispersion with higher fattyacid content. The ionic content also play a major role in such prepa-rations. Study indicates that higher amount of ionic emulsifier isrequired for such modification than lower up to 2% by mass asdocumented for linear chain soft segment based PUDs [26]. Thisis also in remembrance of the fact that the work is focused onpreparing higher molecular weight fully reactive polymer back-bone, dispersed in water and not the short chain free hydroxylcontaining polymer backbone, in which the inclusion of somewhathigher functionality may be possible like in water-based alkyds.
3.3. Molecular weight
The number and weight average molecular weights of the dis-persion films are given in Table 3. Composition B2 containinghigh ionic content had least number and weight average molec-ular weight. This is due to the fact that molecular weight of theDMPA is lower than PE and PD. If there is no significant differencein reactivity between polymeric diol and DMPA, prepolymer chainwill be shorter for higher DMPA content. The other compositions(A2, A3 and A4) had reasonably high molecular weight for goodperformance properties of the film.
3.4. Film formation evaluation by atomic force microscopy (AFM)
Film formation of composition A4 was evaluated before andafter air drying. AFM images as shown in Fig. 6 were obtained
ying (Left) and after drying (Right).
A. Patel et al. / Progress in Organic Coatings 67 (2010) 255–263 261
Composition Water/IPA Water/ethanol Xylene Salt spray test
B2 2 2 1 3A4 5 4 3 5
Fig. 7. Stress- Strain curve of casted coating films of dispersions.
n height mode to evaluate roughness after drying at microscopicevel. From the images it can be concluded that a good coalescence
ith very low roughness values and without important microscopicefects was observed after drying.
.5. Mechanical properties
The mechanical properties of the PUD films are given in Table 5.hey were found to be affected by the amount of oligomer andolecular weight. Films of PUDs with higher oligomer content in
he polymer chain had higher tensile strength and Young’s mod-lus as compared to films of PUDs with lower oligomer contenthereas their elongation at break was lower. The reason is thatith increased oligomer content, molecular branching among theolymer backbone is also increased. Thus mobility of chain seg-ents is reduced. Furthermore, due to oxidative polymerization
ccurring through polyunsaturated fatty acid residues, crosslinkingensity is further increased to synergize above effect. Another rea-on for improved stiffness might be the hard monomers like TMPnd PA used in oligomer and reduced content of linear polyesteriol from the composition. Films based on oligomer PE1 showedigher % elongation and lower tensile strength due to lower molec-lar weight. The stress–strain curves of films of different PUDs arexpressed in Fig. 7.
.6. Contact angle and water uptake
The contact angles of water drop placed on the film of the PUDsre presented in Table 6. Remarkable difference in contact angleetween compositions with different oligomer contents had beenbserved. It increases from 80◦ for composition A2 which con-
Table 6Contact angle data.
Composition Contact angle
B2 75A2 80A3 87A4 92
A3 4 3 2 4A2 4 3 2 3
1: worst; 5: best.
tain 38% oligomer to 92◦ for composition A4 which contain 54%oligomer. The increased contact angle represents lower wettingof the coating films by water and hence increased hydropho-bicity. This reveals that increase in oligomer content increasesthe hydrophobicity of the film. The least contact angle for B2 isattributed to lower oligomer content and higher ionic content.
Water uptake for different compositions is shown in Fig. 8. Theresult revealed that water uptake of film of A4 was the minimumwhile that for B2 was the maximum. Higher water resistance exhib-ited by composition A4 may be attributed to higher hydrophobicityand higher crosslink density.
3.7. Chemical and corrosion resistance
As shown in Table 7 composition A4 showed very good chemi-cal as well as corrosion resistance than others. Improved corrosionresistance of the composition A4 attributed to the higher crosslinkdensity of the dried polymer film resulted from higher incorpora-tion of oligomer in the polymer backbone. Higher oligomer loadingresults in more branched structure, which upon further oxidativepolymerization increases the crosslink density of the polymer film.
3.8. Thermogravimetric analysis (TGA)
The TGA thermogram of cured films of A2, A3, A4 and B2 isshown in Fig. 9. Detailed analysis of the thermogram is representedin Table 8. The onset of urethane bond dissociation is somewherearound 300 ◦C, depending upon the type of isocyanate and polyol
employed. The degradation of the PU films that is observed inthe range of 150–300 ◦C can be attributed to decomposition ofthe urethane bonds, which takes place through the dissociationto isocyanate and alcohol, the formation of primary amines andolefins, or the formation of secondary amines, which results in the
Table 8Thermal stability of PU films with different oligomer content.
Composition Td, on set (◦C) Td, ½ (◦C) Td, max (◦C) Oligomer content
262 A. Patel et al. / Progress in Organic Coatings 67 (2010) 255–263
of cured films of A2, A3, A4 and B2.
lptroPwi13fbfew(bss
3
tdafi3
tFstmfoiiosic
Fig. 10. Tan delta vs. temperature profiles of films of composition A2, A3 & A4.
Fig. 9. The TGA thermograms
oss of carbon dioxide from the urethane bond. The degradationrocesses in the temperature range of 300–400 ◦C are attributedo linoleic acid chain scission. The last steps in the weight-lossate centered at a temperature of 450 ◦C correspond to thermo-xidative degradation of the films. For PU films based on oligomerE2, with different oligomer (PE2) content, the temperature ofeight loss due to dissociation of urethane bonds increases with
ncrease in oligomer in it. It was observed that temperature for0% and 50% degradation shift from 265 ◦C to 293 ◦C and from55 ◦C to 383 ◦C, respectively, when oligomer content increasesrom 38% to 54% in polymer compositions. This can be explainedy the higher molecular branching and crosslink density resultedrom oxidative polymerization of fatty acid residue as discussedarlier. While film of composition B2 has least temperature ofeight losses through whole range due to the high ionic content
8% DMPA) and lower crosslinking. From the above results, it cane concluded that polymer of composition A4 has highest thermaltability than A3 and A2, while composition B2 shows least thermaltability.
.9. Curing studies by dynamic mechanical analysis (DMA)
DMA is the most sensitive method for measuring the viscoelas-ic properties of a polymer as crosslinking proceeds. The crosslinkensities of the films as they cure were expected to vary with themount of oligomer present in the formulation from which thelms were prepared. Changing the amount of oligomer PE2 from7% to 54% changed the viscoelastic property of the films.
The plot of storage modulus and tan ı versus temperature forhe casted films with different oligomer contents is shown inigs. 10 and 11. Here a single tan ı peak is seen implying that theseegmented polymers are phase mixed. The value glass transitionemperature (Tg), obtained as the maximum value of tan ı peak,
oves toward the higher temperature i.e. increases from 11.02 ◦Cor A2, 22.4 ◦C for A3 to 32.05 ◦C for A4 with respective increase inligomer content in the compositions. Also the tan ı peak heights decreased with increasing oligomer content indicating increas-
ng crosslinking density [27]. This is due to the higher branchingf the polymer dispersion as discussed earlier. Also, the increase intorage modulus due to chain entanglements caused by crosslink-ng was observed with increased oligomer content for the sameompositions.
Fig. 11. Storage modulus vs. temperature profiles of films of composition A2, A3 &A4.
ganic
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[25] G. Gündüz, Y. Idlibi, G. Akovali, J. Coat. Technol. 74 (2002) 59.[26] R. Satguru, J. McMahon, J.C. Padget, R.G. Coogan, J. Coat. Technol. 66 (1994)
A. Patel et al. / Progress in Or
. Conclusion
Fatty acid modified polyurethane dispersions were successfullyrepared by prepolymer mixing process but it was found that theunctionality of the oligomer must be adjusted effectively to attainighest possible incorporation of the fatty acid to achieve stable dis-ersion with controlled branched polymer structure of the PUDs.verall PE2 oligomer was found to be more effective in achiev-
ng highest fatty acid loading (28%) in the polymer backbone. Thexidative crosslinking had also been proved effective in enhanc-ng overall performance properties of the PUDs as studied throughFM, TGA and DMA along with chemical and corrosion resistanceroperties.
cknowledgements
The authors wish to express their gratitude to The Director,ophisticated Instrumentation Center for Applied Research andesting (SICART), Vallabh Vidyanagar, India; The Director, Insti-ute of Science and Technology for Advanced Studies and ResearchISTAR), Vallabh Vidyanagar, India and Head, Department of Chem-stry, Sardar Patel University for providing necessary research,esting and library facilities.
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