Effect of PEG on the biodegradability studies of Kenaf cellulose -polyethylene composites

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1 (200) Effect of PEG on the iodegrdility studies of Kenf cellulose -polyethylene composites 1, 4 Behjt, T., 2 Russly, A. R., 3 Luqmn, C. A., 4 Yus, A. Y. nd 5 Nor Azow, I. 1 Deprtment of Food Engineering & Post Hrvest Technology, Irnin Agriculturl Engineering Reserch Institute (IAERI), P.O. Box: , Krj, Irn 2 Fculty of Food Science & Technology, University Putr Mlysi, Serdng, Selngor, Mlysi 3 Lortory Biopolymer nd Derivtives, Institute of Tropicl Forestry nd Forest Products (INTROP), UPM, Serdng, Selngor, Mlysi 4 Deprtment of Process & Food Engineering, Fculty of Engineering, UPM, Serdng, Selngor, Mlysi 5 Deprtment of Chemistry, Fculty of Science, UPM, Serdng, Selngor, Mlysi Astrct: Severl lends of cellulose derived from st prt of kenf (Hiiscus cnninus L.) plnt, with different thermoplstics, low density polyethylene (LDPE) nd high density polyethylene (HDPE), were prepred y melt lending mchine. Polyethylene glycol (PEG) ws used s plsticizer. Biodegrdility of these lends ws mesured using soil uril test in order to study the rtes of iodegrdtion of these polymer lends. It ws found tht the cellulose/ldpe nd cellulose/hdpe lends were iodegrdle in considerle rte. The io-composites with high content of cellulose hd higher degrdtion rte. In ddition, iodegrdility of the io-composites mde up using PEG ws superior to those of the io-composites fricted without PEG, due to the improved wetting of the plsticizer in the mtrix polymer. The results were lso supported y the scnning electron microscopy (SEM). Keywords: Kenf cellulose, polyethylene, iodegrdtion, PEG, soil uril test Introduction Polyethylene (PE) is non-degrdle polymer eing used extensively in mny pplictions. It is lso the first commodity plstic to e used for food pckging, cme into generl use in the 150s. Since then it hs chieved its dominnt position s pckging mteril for wide rnge of foods nd everges ecuse of its reltively low cost, its verstile properties, nd the ese with which it cn e mnufctured nd converted. The min end forms of PE plstics used for food pckging re films, mde y oth cst nd oriented processes, ottles nd other continers mde y thermoforming nd low molding processes. Recently, there is growing interest in replcing some or ll of the synthetic polymers, like PE, to ecome iodegrdle mterils due to their environmentl impcts (Arvnitoynnis et l., 1). Despite of good iodegrdility properties of some nturl polymers such s 3-hydroxyl utyrte (PHB) nd its copolymers nd liphtic polyesters, their higher cost compre to petroleum- sed commodity plstics prevents them from lrger commercil usge nd finds pplictions only in niche sectors (Avell et l., 2005). The est-known renewle resources le to crete iopolymer nd iodegrdle plstics re strch nd cellulose (Chndr nd Rustgi, 1; Selke, 2000). There re lot of studies out using strch in iopolymer production ut fewer for cellulose. Cellulose otined from kenf (Hiiscus cnninus L.), n nnul plnt with mny environmentl dvntges, is good source of iodegrdle polymer (Nishino, 2004). Biodegrdtion occurs with enzymtic ction nd involves living microorgnisms. Almost ll microil degrdtions re crried out y oth fungi nd cteri. There re four iodegrdtion environments for polymeric products nmely soil, qutic, lndfill nd compost. Ech environment contins different microorgnisms nd hs its specil conditions for degrdtion. In soil, fungi re mostly responsile for degrdtion of orgnic mtter including polymers (Bker nd Med, 2000; Chndr nd Rustgi, 1; El-Hdi Adel Ghffr, 2002; Hodzic, 2004; Sridch et l., 2006). *Corresponding Author. Emil: ehjt.tjeddin@yhoo.com All Right Reserved

2 244 Behjt, T., Russly, A. R., Luqmn, C. A., Yus, A. Y. nd Nor Azow, I. The iodegrdtion rte in iopolymers depends on numer of fctors including fier content, the iodegrdility of ech component nd the qulity of the interfce. The fier ddition generlly increses the degrdtion rte of composites nd lkline tretment of fiers produce slightly higher degrdtion rte thn pure mtrix (Plckett nd Vzquez, 2004). Other thn tht, the dditives used (e.g. plsticizers, fillers, etc.) re importnt in iodegrdtion kinetics s well s the type of polymer reflected in moleculr weight, structure nd crystllinity (Guilert nd Gontrd, 2005). In ddition, iodegrdility nd the rte of iodegrdtion depend in generl on the sustrte structure, the sustrte composition nd the existing microorgnisms. Also, the rte of iodegrdtion decreses with the progress of the rection (Sridch et l., 2006). The ojective of this study is to investigte the kenf cellulose-pe iocomposites iodegrdility. Soil uril test is used to determine the iodegrdility on the polymer lends. The effects of plsticizer, PEG, in iodegrdtion of these polymers were lso studied. Mterils nd Methods Mterils The cellulose used in this study ws extrcted from kenf, vriety V36, plnted in Mlysin Agriculturl Reserch nd Development Institute (MARDI). LDPE with density 0.23 g/cm 3, melt flow index 6.0 g/ min nd HDPE with density 0.45 g/cm 3, melt flow index 20.0 g/min were supplied from TITAN PETCHEM (M) SDN. BHD. PEG with verge moleculr weight 000 ws supplied from SIGMA. The soil used for this experiment ws topsoil from Seri Serdng, Selngor, Mlysi with ph Cellulose extrction The cellulose processing ws crried out ccording to Stndrd Test Method, ASTM No.D13-60 nd using method of Hn nd Rowell (16) from kenf fier. Figure 1. Prt of specimens efore filling y soil 30%Cel 40%Cel 50%Cel 0%Cel 30%Cel 40%Cel 50%Cel Figure 2. Biodegrdility of () LDPE/cellulose nd () HDPE/cellulose composites during uril time

3 Effect of PEG on the iodegrdility studies of Kenf cellulose -polyethylene composites %Cel 30%Cel+5%peg 30%Cel+%peg time (dys) %Cel 40%Cel+5%peg 40%Cel+%peg 50%Cel 50%Cel+5%peg 50%Cel+%peg c %Cel 30%Cel+5%PEG 30%Cel+%PEG %Cel 40%Cel+5%PEG 40%Cel+%PEG time (dys) 50%Cel 50%Cel+5%PEG 50%Cel+%PEG c Figure 3. Biodegrdility of LDPE/PEG (Left) nd HDPE/PEG (Right) composites with 30% (), 40% () nd 50% (c) cellulose during uril time Blending PE/Cellulose/PEG formultions were processed using two different types of PEs (LDPE, HDPE) with 0, 30, 40 nd 50% of cellulose nd 0, 5 nd % of PEG, respectively. Predetermined mount of mterils were mixed using Thermo Hke PolyDrive R600/6 lending mchine. Blending ws performed for LDPE t 125 o C with rotor speed 30 rpm in minutes nd 145 o C for HDPE t 30 rpm in12 minutes. Soil uril test A soil uril test ws crried out on lortory scle to exmine the iodegrdility. First, rectngulr sheets (out cm 15 cm 1 mm thickness) of specimens were uried in the soil y rndom pttern (Figure 1). The pot contining the soil nd smples were incuted t lmost constnt temperture of 26 o C for four months. The moisture content ws mintined t 40-50% of the soil s mximum wter holding cpcity. This humidity is optiml for microil ctivity (Chndr nd Rustgi, 1). Also, the pots were covered with plstic film to void wter evportion from the soil surfce. Biodegrdtion ws estimted y monitoring chnges in weight s function of uril time. The smples were removed from the soil every 20 dys. The deris on the specimens ws removed y wshing with wter. The smples were then dried in n oven t 0-5 o C for 24 hours. After drying, they were weighed using n electronic lnce with precision of 0.1 mg. For comprtive reson, the weight of tretments ws normlized to g in the first mesurement.

4 246 Behjt, T., Russly, A. R., Luqmn, C. A., Yus, A. Y. nd Nor Azow, I. Figure 4. Scnning electron microgrphs (Mg. 500) of the frcture surfce of 5lulose+5%PEG for LDPE (Left) nd 5lulose+%PEG for HDPE (Right) composites fter 4 months in the soil Results nd Discussion Figure 2 shows the iodegrdtion test experimentl dt for the lends of LDPE nd HDPE with cellulose. The dispersion of integrity nd rekup of smples ws oserved fter round 40 dys nd incresed during uril time. It cn e noted tht higher content of cellulose hd led to higher degrdtion. These oservtions were in greement with the findings reported in the works y Oldk et l. (2005) nd Kczmrek nd Oldk (2006). They found tht with very smll mount of cellulose (5-15%) in polyethylene (PE) composite, it my not improve its iodegrdility. The iodegrdility in PE films will only hve the pronounced effect if it contins 30% cellulose nd ove. Figure 3 presents the effect of PEG content on the iodegrdtion of LDPE nd HDPE/PEG composites. The compounds show some degree of iodegrdility with incresing PEG. The degrdtion is out 20% for LDPE nd 25% for HDPE compounds fter 120 dys, respectively. From the dt in Figures 2 nd 3, it shows the effect of different cellulose nd PEG loding on iodegrdility of LDPE nd HDPE/Cellulose/PEG compounds. With dditionl PEG, ll PE/cellulose smples show sustntil decrese in their weight in the first 30 dys. It ws noted tht for LDPE/cellulose compounds, ddition of 5% PEG shows higher degrdtion rte fter 120 dys. And for HDPE/ cellulose compounds, ddition of % PEG shows the highest degrdtion rte. It ws lso noted tht 50% cellulose nd 5% PEG for LDPE tretments nd 50% cellulose nd % PEG presented highest degrdtion rte mong ll tretments. Figure 4 illustrtes the Scnning electron microgrph (SEM) results for LDPE tretment with 50% cellulose + 5% PEG nd HDPE tretment with 50% cellulose nd % PEG. From these figures, it is pprent tht cellulose is lmost completely degrded from the surfce of the smples due to soil uril. Conclusion As the iodegrdility test progressed over time up to 120 dys, the composites iodegrdility enhnced with incresing cellulose content ecuse the cellulose is esily ttcked y microorgnisms. It ws oserved tht for LDPE/cellulose composites, with ddition of 5% PEG, it shows etter iodegrdility rte. As in the HDPE/cellulose compounds, higher degrdtion rte ws chieved with the ddition of % PEG. It is due to good interctions etween moleculr structure of mtrix (PE), cellulose nd PEG in ech cse. The results suggested tht it is possile to lend the non-degrdle polyethylene polymer with kenf cellulose in order to improve its iodegrdility. The successful iodegrdility test cn e continued with more percentge of cellulose nd PEG; however, it my e weken the mechnicl properties of the composites. These results were supported y surfce degrdtion of iocomposites oserved through morphologicl study.

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