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Journal of Cleaner Production 57 (2013) 327e334

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Journal of Cleaner Production

journal homepage: www.elsevier .com/locate/ jc lepro

Mechanical, thermal, morphological and leaching properties ofnonmetallic printed circuit board waste in recycled HDPE composites

Shantha Kumari Muniyandi a, Johan Sohaili a,*, Azman Hassan b

aDepartment of Environmental, Faculty of Civil Engineering, Universiti Teknologi Malaysia, UTM, 81310 Skudai, Johor, MalaysiabDepartment of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, UTM, 81310 Skudai, Johor, Malaysia

a r t i c l e i n f o

Article history:Received 1 January 2013Received in revised form16 May 2013Accepted 20 May 2013Available online 1 June 2013

Keywords:Nonmetallic PCBRecycled HDPECompositesMechanical propertiesThermalLeaching

* Corresponding author. Tel.: þ60 197609295.E-mail addresses: shantha87@yahoo.com (S.K.

utm.my (J. Sohaili), azmanh@cheme.utm.my (A. Hassa

0959-6526/$ e see front matter � 2013 Elsevier Ltd.http://dx.doi.org/10.1016/j.jclepro.2013.05.033

a b s t r a c t

The nonmetallic powder recycled from waste printed circuit boards (PCBs) is used as a filler material inrecycled HDPE (rHDPE) in production of rHDPE/PCB composites. This study aims to propose methods forreuse of waste nonmetallic PCBs in a more environmentally friendly way. Mechanical, morphological,thermal and leaching characteristic properties of compatibilized and uncompatibilized composites wereassessed. A good balance between stiffness, strength and toughness was achieved for the system con-taining 30 wt% PCB. Thus, this system was chosen in order to investigate the effect of the compatibilizeron the mechanical properties of the composites. The results indicate that MAPE as a compatibilizer caneffectively promote the interfacial adhesion between nonmetallic PCB and rHDPE. The addition of 6 phrMAPE increased the flexural strength, tensile strength and impact strength by 71%, 98% and 44%respectively compared to the uncompatibilized composites. While, overall thermal properties of thecompatibilized and uncompatibilized rHDPE composites were low, which can be attributed to incor-poration of nonmetallic PCB fillers in rHDPE possessing low thermal conductivity. In terms of environ-mental, after nonmetallic PCB was filled in rHDPE composites, the concentrations of Cu and Br in theleachates were far below the regulatory limits which are only 3.07 mg/L and 3.50 mg/L, respectively. So, itcan be recommended that a balance in mechanical and thermal properties of composites withoutviolating the environmental regulation was achieved with the incorporation of 30 wt% PCB and 6 phrMAPE compatibilizer.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

The production of electrical and electronic equipment (EEE) isone of the fastest growing sectors of the manufacturing industry inthe world. Every year, 20e50 million tonnes of waste electrical andelectronic equipment (WEEE) are generated worldwide (LaDou,2006).

In recent years throughout the world including Malaysia, therehas been increasing concern about the growing volume of end oflife electronics and the fact that much of it is consigned to landfill ordisposed of by combustion without any attempt being made torecycle the nonmetallic materials it contains. It is also being pre-dicted by Department of Environmental Malaysia (Department ofEnvironment, 2009) in their inventory report that the amount ofWEEEwill increase by an average of 14% annually and by the year of

Muniyandi), johansohaili@n).

All rights reserved.

2020, a total of 1.17 billion units or 21.38 million tonnes of WEEEwill be generated (Department of Environment, 2009). One of thisWEEE is printed circuit boards (PCBs). PCBs form about 3% byweight of total amount of electronic waste (Guo et al., 2008). Re-cyclers use different methods to reclaim the metals in PCBs withhigh purity, which can be sold at high price while enormousamount of nonmetallic materials in PCBs (up to 70 wt%) present anespecially difficult challenge for recycling due to their complexnetwork structure. Nonmetallic materials in PCBs are disposed ofby combustion and disposed in landfill as the main methods fortreating nonmetallic materials in PCBs but it may cause secondarypollution and resource wasting (Guo et al., 2010).

Moreover, the recyclers incur additional expenses whenhandling and disposing of these nonmetallic materials as they haveto pay fee when nonmetallic materials are sent to the landfill sitesor waste incineration plants, reducing the recycler’s net revenue.

In this study, the objective of the research is to study thefeasibility of reusing the nonmetallic recycled from waste PCBs inthe recycled High Density Polyethylene (rHDPE) composites withthe aim of developing a new potential reuse of recovered

Table 2Designations of rHDPE/PCB (70/30) with different content of MAPE.

Designation wt% phr

rHDPE PCB MAPE

rHDPE/PCB/MAPE (70/30/3) 70 30 3rHDPE/PCB/MAPE (70/30/6) 70 30 6rHDPE/PCB/MAPE (70/30/12) 70 30 12rHDPE/PCB/MAPE (70/10/18) 70 30 18

S.K. Muniyandi et al. / Journal of Cleaner Production 57 (2013) 327e334328

nonmetallic PCBs and resolving the environmental pollutionsassociated with the recycling of PCBs.

2. Experimental work

2.1. Materials

Tables 1 and 2 show the blends system used in this study. Therecycled HDPE (rHDPE) used in this study was supplied by a localrecycling company in Johor, METAHUB Industries Sdn Bhd. TheMaleic anhydridemodified linear low-density polyethylene (MAPE)used was OREVAC� 18365 supplied by Arkema. The nonmetallicPCB was an industrial solid-waste byproduct, from METAHUB In-dustries Sdn Bhd (Johor, Malaysia). This was in the form of powder.

2.2. Preparations of samples for toxicity characteristic leachingprocedure (TCLP) test

To conduct this test, the pulverized nonmetallic PCB that wassieved was taken. Then prepare as much as 2 L of extraction liquidfollowing the EPA standard TCLP method _EPA 1992a_. Extractionliquid was placed in a bottle High Density Polyethylene (HDPE).Then, a total of 100 g Nonmetallic PCB was placed in HDPE bottles.Sample was prepared with mixing ratio of extraction liquid tononmetallic PCB was 20:1. Bottle is then put into the National Bu-reau Standards leaching machine. Spin the bottle for 18 h with arotation rate of (30 þ 2) rpm. After completion of the leachingprocess, the sample was filtered with borosilicate glass fiber filtersize 0.6e0.8 mm with 50 psi pressure. This process must be doneimmediately after the sample was collected. Sample was placedinto bottles and stored in the refrigerator. After that, samples wereanalyzed by using the ICP MS.

2.3. Compounding and preparation of composites

The nonmetallic PCBs were added to the rHDPE substrate atlevels of 10, 20 and 30wt% and the blends were prepared with a co-rotating twin screw extruder Brabender Plasticoder PL 2000.Adding larger amount of nonmetallic PCBs (>30 wt %) to rHDPEworsened the processibility of the composite material, and createdgreat difficulty for molding process. The rHDPE and the nonmetallicPCBs were dried at 80 �C for 24 h prior to extrusion. The barreltemperature profile adopted during compounding of all blends was210 �C at the feed section, decreasing to 200 �C at the die head andthe screw rotation speed was fixed at 50 rpm.

Composites with MAPE compatibilizer, was extruded under thesame condition used to prepare blends of rHDPE with nonmetallicPCBs. The materials were extruded and palletized. The extrudedmaterials were compression molded into standard tensile, flexuraland Izod impact specimens. The operating temperature was 200 �Cwith 15 min of preheat and another 10 min for compression, fol-lowed by cooling process at room temperature for 5 min beforeremoving it from the mold. Fig. 1 shows the process of the prepa-ration for the rHDPE/PCB composites.

Table 1Designations of rHDPE/PCB and their compositions.

Designation wt%

rHDPE PCB

rHDPE 100 e

rHDPE/PCB (90/10) 90 10rHDPE/PCB (80/20) 80 20rHDPE/PCB (70/30) 70 30

2.4. Measurement of properties

Tensile, flexural and Izod Impact strength tests were carried outaccording to ASTM D638, ASTM D790 and ASTM 256, respectively,by using an Instron (Bucks, UK) 5567 universal testing machineunder ambient conditions. Crosshead speeds of 50 and 3mmmin-1were used for tensile and flexural testing, respectively. Five speci-mens of each formulation were tested and the average values re-ported. The morphology of the composites was examined by usinga field emission scanning microscopy, FESEM to analyze thedispersion of fillers into the rHDPE matrix using fractured surfaces.Prior to the analysis, the fractured surfaces of the specimens weresputter coated with a thin layer of gold. Water absorption test wasconducted in accordancewith ASTMD570-98 to study themoistureintake in the composites. In total, five replicates were tested foreach composite formulation. The weight of the specimens wasmeasured periodically until the samples attained equilibrium. Themoisture absorption was determined as the weight gain over theoven-dry weight of the samples, and calculated using the followingexpression:

Wa ¼ Ww �Wd=Wd � 100

Where Wa ¼ Percentage of water absorption Ww ¼ Weight of wetspecimen Wd ¼ Weight of dry sample.

A differential scanning calorimeter (DSC7-Perkin Elmer) wasalso carried out to study the crystallization and melting behavior ofcomposites. DSC performed by heating composite samples of about

Fig. 1. SEM micrograph of nonmetallic materials from waste PCBs.

Table 3Component of nonmetallic PCBs materials.

Sieve size (mm) Cumulative percentretained (%)

0.3e0.15 500.15e0.9 250.09e0.07 14.3

<0.07 10.7

S.K. Muniyandi et al. / Journal of Cleaner Production 57 (2013) 327e334 329

5e12 mg from room temperature to 180 �C and cooled down toroom temperature. The heating rate used was at 5 �C/min.

3. Results and discussion

3.1. Properties of recovered nonmetallic PCB powders

The waste nonmetallic PCBs used in this study are withoutelectronic elements. A stack of five sieves with hole widths from 0.3to 0.07 mm were selected. The PCBs were sieved to remove im-purities and manually sieved according to BS 812 sieve test: Part103: Section 1 (BSI, 1985). The specimens were agitated for 20 minand the nonmetallic PCBs collected on each sieve were weighed tocalculate the particle size distribution. The component of nonme-tallic PCB materials is shown in Table 3. The nonmetallic PCBs withparticle size of less than 0.3 mm were selected for making com-posites. Microscopic observation shows that most of them aresingle glass fibers and thermosetting resin powders (Fig. 2). A seriesof Energy e dispersive X-ray spectroscopy (EDS) analysis have beencarried out to determine the chemical composition of thesenonmetallic PCBs. It was found that the nonmetallic PCBs containedapproximately 5% of metallic materials such as Cu, Ni, As, and Sn,approximately 60% organic resin materials containing elementssuch as C and H, and approximately 33% glass fibers materials suchas SiO2, MgO, Al2O3. These glass fibers possess many excellentcharacteristics, such as high length diameter ratio (L/D ratio), highelastic modulus, low elongation and low thermal conductivity(Zhen et al., 2009).

3.2. Mechanical properties of the composites

Table 4 summarizes the overall mechanical properties of therHDPE with various nonmetallic PCB contents. Fig. 3 shows thetensile properties of RHDPE/PCB composites. The addition ofnonmetallic PCB has led to a substantial improvement in stiffness ofcomposites with addition of nonmetallic PCB (10e30 wt%). TheYoung’s modulus has increased by about 262.5% upon the incor-poration of 30 wt% PCB. The increase in modulus is mainly influ-enced by the incorporation of rigid fiber/filler reinforcements in tothe polymer making it stiffer (Muniyandi et al., 2013). Interestingly,there is no significant changes were observed in the tensilestrength of rHDPE/PCB composites with addition of nonmetallicPCBs. This might happened due to the immiscibility betweennonmetallic PCB and rHDPE phases as nonmetallic PCB contentscausing voids or weak points inside the specimens. Increasingamount of glass fibers in nonmetallic PCBs also can decreased the

rHDPE

Nonmetallic PCB

Premixed in sealed container

Cut into test specimens

Fig. 2. Production process of th

flow ability of composites and reduced the dispersion of in-gredients, which may lead to poor interfacial adhesion (Guo et al.,2010).

Meanwhile for flexural properties, as can be seen in Fig. 4,flexural modulus of the composites increased by about 96.7% uponthe incorporation of 30 wt% PCB. It increased steadily as the PCBcontent increased from 10 to 30 wt%. The flexural strengthincreased by 20 wt% with the incorporation of 30 wt% nonmetallicPCB. These results are consistent with previous studies, Guo et al.(2010) reported similar results where the flexural strengths ofWPC with nonmetallic PCBs were slightly greater than those ofcontrol specimens. This is because the glass fibers in nonmetallicPCB reinforced the properties of composites. Similar results werealso observed by Zhen et al. (2009) in blends of PP/nonmetallic PCB.They reported that the flexural properties of the composites wereincreased with increasing of the nonmetallic PCB contents from 10to 30 wt%. The maximum increment at the flexural strength andflexural modulus recorded was 86.5% and 133.0%, respectively.Another study by Wang et al. (2010) also reported that using ofnonmetallic powders from PCBs, as an additive to PVC substrate,increased the bending strength up to 39.83 MPa representing123.1% improvement over pure PVCwith the incorporation of 20 wt% PCB. The increasing trend in flexural properties is expected since,with such millions of glass fibers and good compatibility betweenthe nonmetallic PCBs and matrix, there are mass excellent sup-porting bodies and appropriate interfacial adhesives are formedbetween the particles and matrix (Zhen et al., 2009). All the pre-vious research showed that the outstanding characteristics of thenonmetallic materials in PCB is its flexural strength. Therefore, theyconcluded that this characteristics is good for products that mainlybear bending stresses.

Apart from that, Fig. 5 shows that there are decreases in elon-gation at break and Izod impact strength with incorporation of 10e30 wt% nonmetallic PCB contents. It implies that, increasing fillercontent can reduce the mobility of polymer chain thus restricted itsmovement (Raymond and Charles, 1981). The reinforcements alsowill cause stress concentrations and exhibits brittle nature whichresulted in lower elongation at break and impact strength. Theseresults explained that glass fibers in nonmetallic PCB enhanced thestiffness of the composites but reduced the performance of thetoughness.

Due to the poor adhesion between the rHDPE matrix and thenonmetallic PCB fibers, MAPE compatibilizer has been used toimprove the adhesion between the fibers and the matrix which cansignificantly improve the performances of the rHDPE/PCB com-posites. System containing 30 wt% PCB was chosen to investigatethe effect of compatibilizer on the mechanical properties of thecomposites. The effects of the MAPE contents (3, 6, 12 and 18 phr)on the mechanical properties are depicted in Table 5. Fig. 6 showsthat the tensile strength and Young’s modulus of the compositesincreasewith MAPE contents. The addition of 6 phr MAPE increasesthe tensile strength and Young’s modulus of composites by 98% and38%, respectively, when compared to uncompatibilized composites.The tensile properties reached maximum at a MAPE content of6 phr, with a decrease with further addition of MAPE. The sametrend were observed in flexural properties as can be seen in Fig. 7,

Thermoformed into sheets

Extruded into thread

Compounded using twin screw extruder

Palletized

e rHDPE/PCB composites.

Table 4Mechanical properties of the rHDPE with various PCB contents.

PCB content (wt%) 0 10 20 30

PropertyTensile testingYoung’s modulus (GPa) 0.64 0.85 1.32 2.32Tensile strength (MPa) 7.95 6.67 6.71 6.78Elongation at break (%) 3.5 2.8 2.0 1.6Flexural testingFlexural modulus (GPa) 1.68 7.32 13.81 16.41Flexural strength (MPa) 10.40 10.71 11.00 12.44Impact strength (J/m) 59.6 48.3 44.2 42.5

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0 10 20 30 Flexu

ral S

tren

gth

(G

Pa

)

Flexu

ral m

od

ulu

s (G

Pa)

PCB Content (wt%)

Flexural modulusFlexural Strength

Fig. 4. Effect of PCB contents on the flexural strength and flexural modulus of rHDPE/PCB composites.

S.K. Muniyandi et al. / Journal of Cleaner Production 57 (2013) 327e334330

flexural properties achieved a maximum level when the amount ofcompatibilizer was about 6 phr with increment in flexural strengthand flexuralmodulus by 71% and 69%, respectively. Further additionof MAPE up to 18 wt% caused a slight reduction in flexural prop-erties. The improvements in tensile and flexural properties arebelieved to be due to the MAPE being able to associate with thefunctionality of the nonmetallic PCB, which enhanced the interfa-cial adhesion between the nonmetallic PCB and rHDPE matrix.However, MAPE is noted to have enhanced the properties of rHDPE/PCB composites up to certain level only. The presence of excessivecompatibilizer amounts causes a significant reduction in flexuraland tensile properties of the composites and this demonstrates thatexcessive MAPE does not favor the improvement of mechanicalperformances. This is in agreement with Sathe and his co-researchers, whereby they stated that up to a saturation level ofthe compatibilizer, its molecules are located in the interphase be-tween the matrix and the dispersed phase (Sathe et al., 1996).However, when the concentration of a compatibilizer is above thesaturation level, only a part of the molecules locates in the inter-facial area, and the excess is dispersed in the matrix affecting itshomogeneity and consequently the mechanical properties of theblends.

Same trend were observed in the elongation of break andimpact strength for rHDPE/PCB composites (Fig. 8) whereby, whencompatibilizer MAPE was introduced, the rHDPE/PCB systemshowed an increasing in elongation and impact properties and hadcaused a balance in properties between the matrix and filler, butbeyond 12 phr of MAPE contents, the elongation at break andimpact strength began to achieve the constant value. This mighthappened because at high maleic anhydride contents, in-compatibility ‘problems’ could arise. Therefore, high contents ofsuch oligomers can adversely affect the elongation at break andimpact properties. It seems that the incorporation of MAPE im-proves the toughness and overall performances of the blends ifused in sufficient amount.

4

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0 10 20 30 Te

ns

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tre

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(M

Pa

)

Yo

un

g's

m

od

ulu

s (G

Pa

)

PCB Content (wt%)

Young's modulusTensile Strength

Fig. 3. Effect of PCB contents on the tensile strength and Young’s modulus of rHDPE/PCB composites.

3.3. Morphology of the composites

FESEM was used to examine the morphology of the blends.Fig. 9aed show the SEM images of fractured surface of rHDPE/PCBcomposites filled with 0, 10, 20 and 30 wt% nonmetallic PCB,respectively. It can be observed that, without compatibilizer deepvoids and gaps appeared in the matrix indicating lack of sufficientparticle bonding as shown in Fig. 9bed. There were obvious sepa-ration between rHDPE and the nonmetallic PCB as well, because ofthe incompatibility between matrix and fillers. Large holes also canbe seen due to pullout of glass fibers in nonmetallic PCBs from thematrix (Fig. 9b). The gaps between the matrix and the fillers werereduced when 6 phr of MAPE compatibilizer were added (Fig. 10a).The adhesion between glass fibers and matrix was seen by a closerobservation at higher magnification in Fig. 10b. There was filler/matrix filled in the gap of glass fibers, which showed a very stronginterfacial bonding between glass fibers in nonmetallic PCBs andrecycled HDPE. The good adhesion between glass fibers and matrixcan strengthen the mechanical properties of the composites.

The MAPE significantly improved the compatibility between thematrix and nonmetallic PCB fillers, and the matrix was bonded tothe fillers well, thus improved the compatibility and interfacialadhesion of the rHDPE/PCB composites. However, with incorpora-tion of 18 phr of MAPE, it can be seen that the excessive use ofcompatibilizer results in the formation of a weak elastomeric phasethat starts to deteriorate the composite’s mechanical properties(Fig. 10c) which in agreement to the results obtained in mechanicalproperties earlier.

3.4. The concentration of heavy metals and Br leached from therHDPE/PCB composites

Nonmetallic PCB waste may contain various metal elements,likely Cuwith the highest contents and brominated flame retardantas well. Therefore, it is feasible to determine the concentration of

0

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60

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0 10 20 30 Elo

ng

atio

n a

t B

re

ak

(%

)

Im

pa

ct S

tre

ng

th

(J

/m

)

PCB Content (wt%)

Elongation at BreakImpact Strength

Fig. 5. Effect of PCB contents on the impact strength and elongation at break of rHDPE/PCB composites.

Table 5Mechanical properties of rHDPE/PCB (70/30) with various MAPE contents.

MAPE (phr) 0 3 6 12 18

PropertyTensile testingYoung’s modulus (GPa) 2.32 2.8 3.2 2.34 2.32Tensile strength (MPa) 6.67 11.35 13.23 12.78 10.25Elongation at break (%) 1.6 1.9 2.0 2.24 2.22Flexural testingFlexural modulus (GPa) 16.41 24.52 27.68 21.61 20.63Flexural strength (MPa) 12.44 17.50 21.26 20.00 14.26Impact strength (J/m) 42.5 48.4 52.6 61.1 60.0

0

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0 6 12 18

Flexu

ral S

tre

ng

th

(M

Pa

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Fle

xu

ra

l m

od

ulu

s (

GP

a)

PCB Content (wt%)

Flexural Modulus

Flexural Strength

Fig. 7. Effect of MAPE content on the flexural strength and flexural modulus of rHDPE/PCB composites.

S.K. Muniyandi et al. / Journal of Cleaner Production 57 (2013) 327e334 331

heavy metals, especially Cu and toxic compounds such as Brleached from the raw nonmetallic PCB powders and rHDPE/PCBcomposites. The EPA standard TCLP method_EPA 1992a_ wasemployed in this lecaching test. TCLP tests were done in threereplicates and the average value was reported. The rHDPE/PCBcomposites with maximum content of the nonmetallic PCB (30 wt%) were selected to study the leaching characteristics.

Table 6 lists the concentrations of metal ions leached fromnonmetallic PCB powders and rHDPE/PCB composites. From theleaching results of nonmetallic PCB powders, Cu was identified asthe most critical metal with the highest concentration of metal ionleached (59.09mg/L) among all the othermetals but it is still withinthe regulatory limits.

However, after nonmetallic PCB was filled in rHDPE composites,the concentration of Cu in the leachates were far below the regu-latory limits which is only 3.07 mg/L. It is reduced by almost 19times the concentration of Cu in nonmetallic PCB powders. This isdue to the encapsulation of the resin matrix of composites. Theconcentration of Cu was the highest among all the other metal ionsin the leachates mainly due to the highest residual Cu particles inthe nonmetallic PCB waste compared to other metals. Normally, Cuparticles in the nonmetallic PCB waste were encapsulated by resinpowder and glass fibers, making it difficult and hard to separate theCu particles from the nonmetallic materials completely.

Meanwhile, for the other metallic constituents as listed inTable 6, all the ion concentrations were far below the regulatorylimits and identification standards for hazardous waste.

Like the concentration of Cu, Br concentration leached from thebrominated compounds (such as brominated flame retardant) inthe nonmetallic PCBs waste is considerably high with concentra-tion of 14.0 mg/L. However, there is no relative standard forleaching of Br. When rHDPE was filled with nonmetallic PCBs, asexpected, concentrations of Br leached from the composites werereduced significantly up to 3.50 mg/L and it is far below the con-centration of Br leached from the nonmetallic PCBs alone.

4

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0 6 12 18

Te

ns

ile

S

tre

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(M

Pa

)

Yo

un

g's

m

od

ulu

s (G

Pa

)

PCB Content (wt%)

Young's modulusTensile Strength

Fig. 6. Effect of MAPE contents on the tensile strength and Young’s modulus of rHDPE/PCB composites.

Based upon the leaching characteristics, it can be said that,utilization of nonmetallic PCB waste as filler in composites candramatically restrain the solubility of heavy metals in leachate so-lution. In a word, the nonmetallic PCB in composites was not amajor concern in terms of environmental assessment since all theconcentrations of metal ions and Br in the leachates are consideredlow and complied with the regulatory limits. Hence, it is concludedthat nonmetallic PCBs can be successfully reuse in the rHDPEcomposites or any other practical composite products.

3.5. Thermal properties of rHDPE in uncompatibilized andcompatibilized rHDPE/PCB composites

The melting point (Tm), enthalpy of melting (DHm) and crystal-linity (% Xc) of rHDPE and the composites are listed in Table 7. DSCmelting thermograms of rHDPE/PCB blends are shown in Fig. 11. ForrHDPE component, the Tm is detected at 108.17 �C, DHm and %Xc are31.65 J/g and 10.80%, respectively. The Tm of rHDPE/PCB compositeswith 10, 20 and 30 wt% nonmetallic PCBs are close to those ofrHDPE with no significant changes. This behavior is normal forimmiscible polymer blends in melt state (Wilfong et al., 1986). DHm

and %Xc of rHDPE component decrease with adding nonmetallicPCB fillers in to the blends.

By adding 6, 12 and 18 phr of the MAPE compatibilizers inrHDPE/PCB (70/30) composites, Tm of rHDPE in the compositescompatibilized with (6e18 phr) MAPE is shifted to temperatureslower than those of the uncompatibilized composites. Thesemelting point displacements indicated compatibility between thecomponents with the presence of the compatibilizer that caused anincrease of the mechanical properties. The %Xc of rHDPE compo-nents decrease with increase of the MAPE contents. The loweredcrystallinity level suggested that the compatibility between rHDPEmatrix and nonmetallic PCB fillers was improved by the compati-bilizer, and the perfection of rHDPE crystals was reduced. Theseresults can be rationalized by considering the effect of the misci-bility of the functionalized polyolefins with the rHDPE phase at theinterface of the melt (Pracella et al., 2002).

0

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0 6 12 18 Elo

ng

atio

n a

t B

re

ak

(%

)

Im

pa

ct S

tre

ng

th

(J/m

)

PCB Content (wt%)

Impact StrengthElongation at Break

Fig. 8. Effect of MAPE content on the impact strength and elongation at break ofrHDPE/PCB composites.

Fig. 9. SEM photographs of the fracture surfaces of rHDPE/PCB specimens with different contents of nonmetallic PCBs: (a) 0 wt%, (b) 10 wt%, (c) 20 wt% and (d) 30 wt%.

S.K. Muniyandi et al. / Journal of Cleaner Production 57 (2013) 327e334332

Overall, reduction of the Tm and DHm in compatibilized anduncompatibilized rHDPE composites can be attributed to incorpo-ration of nonmetallic PCB fillers in rHDPE, possessing low thermalconductivity. There are obvious differences in Tm, DHm and % Xc be-tween thevirginHDPE and recycledHDPE and its blends. However, adirect comparison of the composite properties from virgin andrecycled HDPE is not always possible because it needs to be pointedthat there are many grades of virgin and recycled HDPE products.

3.6. Water absorption rate of compatibilized and uncompatibilizedrHDPE/PCB composites

Table 8 shows the water absorption rate of compatibilized anduncompatibilized rHDPE/PCB composites. Although not much dif-ferences can be seen in water absorption rate with different con-tents of nonmetallic PCBs, but composites with 10 wt% nonmetallicPCB showed the largest water absorption. This is unexpectedbecause nonmetallic PCB materials consisting glass fibers and resinpowders are water repellent and have much lower water absorp-tion capability (Guo et al., 2010). However, the reasons maybecomplex and can be explained by the micro-cracks and voids in thematrix formed during the compounding process. The water

absorption of thermoplastic filled with filler depends on the gapsand flaws at the interfaces, micro-cracks and fine pores in thematrix formed during the compounding process.

The presence of voids and defects located in the filler/matrixinterface was due to poor dispersion of the filler in the polymermatrix. The number of voids and defects between the filler andpolymer matrix decreased as the compatibilizer MAPE was incor-porated in the composites. The incorporation of the compatibilizerinto the composites consistently reduced the water absorption rateand the results are closed to the unfilled rHDPE. The MAPEimproved the interfacial adhesion between nonmetallic PCB andpolymer matrix, leading to less micro-voids and fiber-polyethylenedebondings, in the interface region. The SEM images confirmed thatthe filler was strongly bonded to the polymer with incorporation ofMAPE compatibilizer (Fig. 10a).

3.7. Potential applications of rHDPE/PCB composites

This research expects to develop a toughened composite fromrecycled rHDPE and waste nonmetallic PCB with balanced me-chanical properties. The success of this research will contribute tomany potential specific application in the future. Analysis of the

Fig. 10. SEM photographs of the fracture surfaces of rHDPE/PCB/MAPE specimens with different contents of MAPE: (aeb) 6 phr and (c) 18 phr.

S.K. Muniyandi et al. / Journal of Cleaner Production 57 (2013) 327e334 333

mechanical properties indicates that the recovered nonmetallicPCBs waste can best be used to make products which enduregreater bending stresses because of its excellent flexural strength.Recently, many researchers are exploring to reuse these nonme-tallic PCBmaterials in a more profitable waywithout neglecting theenvironmental problems associated with it. The nonmetallic ma-terials has been used in China in making few practical productssuch as sewer grates and surfboat in amusement park. The main

Table 6TCLP Result.

Method reference Parameters Units Results

Nonmetallic P

USEPA 6010 B Arsenic mg/l <0.05USEPA 6010 B Barium mg/l 2.462USEPA 6010 B Cadmium mg/l <0.01USEPA 6010 B Chromium mg/l <0.01USEPA 6010 B Lead mg/l 0.074USEPA 7470 A Mercury mg/l <0.001USEPA 6010 B Nickel mg/l <0.1USEPA 6010 B Selenium mg/l <0.1USEPA 6010 B Silver mg/l <0.01USEPA 6010 B Zinc mg/l 0.436USEPA 6010 B Copper mg/l 59.09e Bromine mg/l 14.0

advantages of using these products made of nonmetallic PCB arelower in cost and better mechanical strength especially flexuralstrength (Mou et al., 2007). Besides that, in term of cost, usingwaste materials will give extra effect of saving raw materials sincethe cost of waste materials are considered zero. From this study, asmuch as 30 wt% nonmetallic materials recycled from waste PCBscan be added in the rHDPE composites without violating theenvironmental regulation.

DOE limit Remarks

CB rHDPE/PCB composite

<0.05 5 Pass<0.1 100 Pass<0.01 1.0 Pass<0.01 5.0 Pass<0.05 5.0 Pass<0.001 0.2 Pass<0.1 100 Pass<0.1 1.0 Pass<0.01 5.0 Pass<0.1 100 Pass3.07 100 Pass3.50 e e

Table 7Melting temperature (Tm) and percent crystallinity (%Xc) of rHDPE in uncompati-bilized and compatibilized rHDPE/PCB composites.

Sample HDPE component

Tm (�C) DHm (J/g) %Xc

vHDPE (100) 115.83 123.52 42.16rHDPE (100) 108.17 31.65 10.80rHDPE/PCB (90/10) 107.67 25.54 8.72rHDPE/PCB (80/20) 107.67 16.37 5.59rHDPE/PCB (70/30) 107.17 12.56 4.29rHDPE/PCB/MAPE (70/30/6) 107.33 10.42 3.56rHDPE/PCB/MAPE (70/30/12) 106.83 9.09 3.01rHDPE/PCB/MAPE (70/30/18) 106.67 8.81 3.10

0

10

20

30

40

50

60

70

0 50 100 150 200

He

at F

lo

w E

nd

o U

p (m

W)

Temperature ( C)

vHDPErHDPE90/1080/2070/30

Fig. 11. DSC melting thermograms of rHDPE/PCB blends.

Table 8Water absorption rate of compatibilized and uncompatibilized rHDPE/PCBcomposites.

Sample Water absorptionrate (%)

rHDPE 0.32rHDPE/PCB (90/10) 0.80rHDPE/PCB (90/20) 0.50rHDPE/PCB (90/30) 0.43rHDPE/PCB/MAPE (90/10/6) 0.38rHDPE/PCB/MAPE (90/10/12) 0.36rHDPE/PCB/MAPE (90/10/18) 0.37

S.K. Muniyandi et al. / Journal of Cleaner Production 57 (2013) 327e334334

4. Conclusions

Mechanical properties have been successfully improved withthe incorporation of MAPE compatibilizer in rHDPE/PCB compos-ites. However, beyond 6 phr of MAPE compatibilizer, the mechan-ical performances of the composites began to achieve constant

value. SEM analysis showed that compatibilizer significantlyimproved the compatibility between the rHDPE matrix andnonmetallic PCB fillers thus, improved the mechanical perfor-mances of the composites. Thermal properties of the uncompati-bilized and compatibilized composites decrease with the additionof the nonmetallic PCBs since incorporation of nonmetallic PCBfillers in rHDPE possessing low thermal conductivity. The waterabsorption rate of the uncompatibilized and compatibilized com-posites are generally low since the nonmetallic PCB materials arewater repellent and have low water absorption capability.Regarding the leaching properties, after nonmetallic PCB was filledin rHDPE composites, the concentrations of Cu and Br in theleachates were reduced and far below the regulatory limits.

This study shows that a balance in strength, stiffness andtoughness of the composites without violating the environmentalregulation was achieved with the incorporation of 30 wt%nonmetallic PCB and 6 phr MAPE compatibilizer.

Acknowledgments

We would like to extend our gratitude to Univesiti TeknologiMalaysia (UTM) and Ministry of Higher Education (MOHE) for thesupports and grant awarded (Vot No: Q.J130000.2617.09J06).

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