The effect of electron beam irradiation on the properties of low density polyethylene (LDPE, LH0075) and ethylene vinyl acetate (EVA, with 18 %VA) blends were investigated. The improvement of the measured gel content, stress at ultimate, strain at Auto breaks and transition temperatures (Tg, Tm) have confirmed the positive effects on blends but ineffective in density of blends

Hassan, Azman

Sabet, Mazyiar

Wahit, Mat Uzir

English

Universiti Teknologi Malaysia Institutional Repository

rte proceear:rgs or TAFSS 2OO7Rdsromr Anrual Fundrrent l sde@ s€nhd 2007Modified effects of LDPE/EVA blends by electronbeam irradiationMMyisr Sabet, Amsn HassaD, Mat UziI WlhifFacuhy of Chedical a"d Natwal R?.sources Eryi"eeriry, Uniwnity TechtlologMalalsia PTM, 81310 Skudai, Johor Bahm, Malq,siaAbstractThe etrect of el€ctron bean inadiation on the propedies of low density poly€thyl€ne(LDPE, LH0075) and €thylene vinyl ac€tate (EVA, with 18 ToVA) bl€nds wereinvestigated. The improvement of the measured gel conient, sh€ss at ultimale, stain atAuto breaks and transition tempqatures (Tg ,Tm ) have cotrfimed the positive etrects onbleds but inefectiv€ in d€nsity ofblends.ItrtroductionBlending is a well kno*n method of modifying properties of polym€r. L is aneconomically viable flnd versatile way to produce new materials dd to ov€r comedeficiency in son€ material chaieteristics. Thete has been an irnpressive dout ofrese@h and developm{t work carried out in radiarion processing ofpolyner blends forelechical insularion purposes, Spenad€ et al. (19?5) found that by blending 10-30 wt%rubb€r to polyethylene can produce s wire insulation that is more flexible and thus easierto install and splice. Low densit lolyethylene (LDPE, LH0075) cm be radiationcrosslinlcd without any addirion of spechl addtives or crosslinking agents. Radiationcrosslinkins makes this honopolyner harden dd split 6ily at low temperature (ZhangHui and Xu Jiufir 1993). On th€ other hand, ethylene vinyl ac€tate (EvA, with 18 %VA)has a nrbbery property that is highly flexible. Ethylene vinyl aceLate (EVA, with l8%VA) can attain th€ same degree of crosslinking 6 LDPE but at lower dose (LDPELH0075 at 210 KGY ad EVA wi.h 187oVA at 140 KGY). Ther€fore it is possible byblendins certnin amount of EVA wi.h LDPE to inprove the inadiation ctosslinkingperfornance of LDPE. The €ffect of€lectron bem iradiation md EVA cont€nt upon thesel-fonning process in LDPE-BVA fi'rs have be€n studied by Mateev dd Karageorgi€r(1998) and Janalih, Sharifah together with Karnaruddin (1999). This paper will presdtson€ fiiding on th€ elTect of elechon beam imdiation on the propenies of LDPEEVA2B-2s t ay2407rbnu s na rmlitne lor Fundomental scl6n6 stud63UnteF Teknolosilra]at€latE Ptuc..d/re. ot ttAFss 2007Expelimentdi. Mitertsls:LDPE wirh density of 0.92 grlcml and rn€lt flow index of 0.83 grl cm3 and EVAwidll8% vinyl ac€tate conient and melt flow ind€x of 1.83 grllonin w€re purchas€dfiom lran( pet ochenical complex of iban khotrt€iny) md China (attachd Tane elfii. Simple Pr€pantioniLDPE and EVA werc bletrded together at ratios of 90/10, 8020 and 70/30 by usingBrabender Plasticordei Pl 2000 Model lab_ station TYPE 815801 at 50 'c and 130 RPM.The blended sanples were then coEpression moulded into r€ctanguld sheets (150x200mm) of2nn thickness under lton pressur€.iii. Irrrdtrdon:Irradiation was carried out under air atlospheric by usins a rhodotron 200TT, hishvoltage, 5-10MeV md 100x2 Kw power. Ii.adiation doses were s€lect€d in the range of120-240 KGY and 30 KOY/pass.iv. Gel Cont€nt:Gel content was det€rmined by reflruiag the sanple with xylene for 24 nr. The renaininginsoluble smple wa! rinsed with melhanol and dri€d in a vacuum oven at 70'c to aconstant weight. It is shoM in Fig. 1 that gel content increased rapidly up to 200 KCY inall sanples atrd then increase gadually with futher inciease in dose. Gel contentincreas€d by incrasiry EVA €ontent in blends.The highert gel content was for pule EVA .B!ms (1979) proposed that part ofthe reasonfor superior crosslinking in EVA than the hornopolymer. This finding was bas€d on thecontinuilg consensus (Lawton et., 1958; Patel and K€ller, 1975) thai at mbientconditions mdiation crosslinking occws mainly within the amorphous reeions of aloly€thylene. Ir is interesting to note thar gel content of LDPE€VA blend showedaverase value of gel content fo. pure LDPE and EVA.v. Hot Set test:Hot set test was done to measure the elongation of sanples for static load at a fixedtemp€rature. Measur€ments were carded out_ iD an oven at 200"c with no-mal sirconditiod. Th€ sample loading was 20 N/cn' lhe elongation between two marks wasdetermined after l5 min heatins ofthe sample.vi. Measurement of mechanical properties:Tensile tests w€re canied out on dumbell shap€d of specin€ns by using Instron tensilenachin€ model 441 t with a crosshead spe€d of solfir/mir accoiditrg to ASTM D'638.97Ih. Pnc.edinss ol RAFSS mo|R€sult and discussionCel content:Fig.l shows th€ relation ship betwem the gel conienl with iradiatio! for LDPE, EvAud LDPEDVA blends. Uninadiated samples wer€ found solubl€ in ho. xylene, howeverupon iEadiation they underso crosslinking and as a result of network formation in th€pob{ier, solubilit ofthe samples was reduced significantly. It is shown in Fig.l that gelcontent increases rapiilly up to dose 200KGY in all sanples ud tho increases gnduallywith turth€r increase in dose. Incr€ase in 8el content in bl€nds was enhanced byincreasing EVA cont€ni Gel content wa! highest for pure EVA. Burns (1979) proposethat pert of the re3son for superior crosslinldng in EVA than the honopo\mer- Thisfinding was b6ed on the continuing consensus (Lawton et al., 1958; Patel and Keller,1975) that at ambied conditions radiation crdslinking occurs nainly with in thea.morphous regions of a polyethylen€. It is interesting to note lha! gel conient ofLDPE€VA blends showed average value of gel contetrt for pure LDPE and EVA.aE90.080.070.060.050.0160 190Dos6 (KGy)+IDPE 100%-|-EVA 100%Fie 1. Etrect of absorbed dose on gel conieni ofLDPE, EVA and blendsi. Hot Set test:Hot Set provides a quick check on crosslinking of samples and can be conelakd with gelcodent. This t€st was cdied out and the results are shown in table . I it was found ihatUninadiated sanples failed the t€st irnm€diately mder el€vated terpenture 20cfc andload 20 N/crn for 15 min. Irradist€d sanples up to 120 KGY still failed in this tesl but it98Ih. Ptuc.e.Itlss ot RAFss 2007took more time. However, r€sults of sanples at 200 'c temperatui€ irlprov€d as the doseincr€a!€d. These achievernents are due to formaton mor€ uosslink€d polym€r bleod as€vident by th€ g€l content. It is obvious that EVA reach€s a certain value of hotelonga.ion at nuch low€r dose ftu LDPE.Th€ pedormances ofthe blends rely on th€ amount ofEVA in the blends. This behavioris b€liev€d to be due to the nfiIe ofEVA hich more €asily crosslinks when expose toelectron beam. Wi€sn er (1991) report€d that ditr€rent polymer structur€s requiredifferent specific numbeN of crosslinking for certain reduction of defomation caused byahe load in the hot set test. Formation of ad€quate radiation crosslinking n€t work in thepobmer rend€r the pobmer better elongation at high temperahne. It is shown that hotelongation value was noted when gel content value reached more than 75% for puepolym€rs as well as th€ir blends.Tible 1. Hot s€t test results a 200 0c under 20 N/cm'1 load for lsminii. MechanicalProperties:Fig .2 illustraies the tensile strength, Ts as a tunction of inadiation dose. It was shownthat upotr inadiation Ts of LDPE increased rapidly up to dose 200 KGY and remainedIOO% LDPE90% LDPE-1O% EVA80% LDPB20%EvA10o/oLDPE-3t%wA100% EvADoserKGY)0Fails Fails Fails Fails Fails30Fails Fails Fails FailsFails (t5 sec)60 Faik r0.5 rnin) Fails (40 sec) Fails {l rninr Fails (1.5 min) Fails (2 min)90 Fails (0.7s mD) Fails al min) Fails (l.5 minl Fails (2 nin) Fails (3 min)120 Fails (2 inin) Faih (1J5 sec) Faibrl48 sec) Fails (247 sec) Fails (6.5 min)150 Fails (4 min) Fails (5.5 nin) Fails (6.5 min) Fai ls (7.5 min) 160%180 Fails (4.s min) Fails (7.3 nin) 208% 197.30/, 78%210 t85% t830/o t66.7% 146j% 64.5%240 t47% 1t8j% 1t7.95./o 1090/0 45%99m. P@..rnss of ttAFss 2017constant with turther incr€ase of radiation dose to 240 KGY. It w6 reported by Bums(1979) that in ord€r to set optinum mechanical properties fion BVA the iiradiation doseshould not exceed 200 KGY. TeNil€ shength of the blends also inoeased with the doseand d€cr€ded after 210 KGY. The reduction is nost likely to be caused by th€ chairscission ar hish dose. It is obvious that te.sile str€ngth of the blends was ascertained byrhe anount of EVA in th€ blends. Blend wiih high content of EVA showed high value oftensile strength.--.- LDPE 100%{- EVA 100%o- 40uJ(,--zLrlz-10150DoSE(KGy)200Flg 2. Effect ofabsorbed dose on tensile stenelh ofLDPE, EVA and blendsFis .3 shows ihe r€lationship between elongation at break and irradiation dose of t]lesamples. Cenerally increasing inadiation dos€ results in reduction in elongation ai breakofth€ LDPE, EVA and blends. As the dose increas€s nore crosslink! are produc€d in th€sanpl€ nal x which Fevents rhe stuotural reorganization dur;ng dmwing (De Bore andPeming, 1983). Therefor€ by incr€asine tbree- dinensional and gel- like structulesintemal chain nobiliry and elonSation d€deasas. . It is obvious fton Fig.3 that€longation at break of th€ blends w€r€ ascert ined by the amount of EVA in the blends.Blend with hish content of EVA showed high value of elongation at break. As a100rh. P66.dkss.r RAFss 21o?consequenc€ elongation at break ofblends has in ag.e€ment with th€ amounr of EVA inblends.650.: 600;. .^E.5 450ftP' 4ootr 3503000 50 100 150 200 250Dose (KGy)+LDPE 100%Fig J Emecr of absorbed ose on etongaLion ar break orLDPI. EVA and blendsFtg 4.Effect ofabsorbed os€ on density ofLDPE, EVA and blends.0.990.980.97^E 096; 0.95fi 0.s40.93o.920,91101Ih. PtuF..tlnss or FuFss 20orFig .4 shows lhe plot of conposition dependence of the densiry of the sarnple withircreasins imdiation doses. It was found that at the beginning of inadiation the dmsityof LDPE EVA and blends siadually decreased (up to 120 KGY) but with tur.herabsorbed dose there is no sisrificant changes. Fig.5 shows th€ plot of €omposinondeDendefte of th€ hardness ofihe sanPle with inc.easing irndiation dose. In d€finition,h;dness is eenemlty refmed to resistance ofrnat€rial io local defomaiion (Vishu Shah,1984).It was found tllat the hardness of LDPE increased gmdually with incr€ase iradiationdos€ up to 240 KGY. In agreenent with the results of tensile srrength dle hardness ofEVA incr€as€d up to 210 KGY and th€n decreas€d with turther increased in radiationdose. Hardness of the bl€nds depended on the polymer composition s€emed to showslight ircreared in hardrcss. Thus it is evid€nt that the enhancenent in hardn€ss ofLDPE, EVA .nd bl€nds is due to the formation of ndiation caosslinlG as conflnn€d byo=oE6)534945413733.--._ LDFE,-"1- 90% LDPE10% F,/A"'r- 80% LDFE20% EVA--x- 70% LDPE30% EVA-i(- EVA100 150 200 250Absorbed dose (KGY)Fts 5. Effect of absorb€d ose on hardness of LDPE, EVA and blends102m. Pb@.dkss .r RiFss 2tx7ConclusionThis study has confimed that electron bem radiation has positive effects on theproperties ofLDPE, EVA and bl€nds. It was foud that:I . Crosslinking of .he LDPE, EVA and blends increase as the dose incr€ase up to240 KGY. The amount of crosslinking in the blends increale as the conopositionofEVA increase.2. The tensile strength of LDPE increased when inadiated up to 240 KGY. Thetensile strensth of EVA and th€ blends increased when inadiated up to 200 KGYand decreased with turther increase in dose.3. The d{siq ofLDPE, EVA and blends did not change significantly with increaseinadiaiion dose up to 240 KGY.4. The hardness of ihe inadiated samples inproved due to th€ formation ofmdiationcmsslinks. Hardrcss of EVA was found to be hish€r than .hai of LDPE whereashddn€ss ofthe blends depended on the polymer composition.R€fer€ncesl Bums.N.M"The radialion crosslinking of €thylene copolyneN". Radiationphysics and chemistry 14,797-808, 1979.2. De Bo€r.J.Pemings.L.," The effect ofpe ant chains on the elasticity behavior ofpoly€thylene networks". Colloid pob.mer sci€nce 26 t, ?50, 1983.3. Lflwron. E.J.Balwit.J.S.Powell.R.S." Etrect of physical state duing the electroniradiation of hydrocarbon polymeN. Pari 1 TIIe influ€n@ of physical state onreactions occuning in polyethylene dlring and following th€ inadiation".J.Pobn€r Science 32,257, 1958.4. Mat€ev.M.,Karageorgev.S." The effect of electron beab inadiation and content ofEVA upon .he gel forming process in LDPE-EVA filrn". Radiaiion physics andch€mistry 51, 205, 1998.5. Patel.G.N.Keller.A." Crystallinity and .he effect of ionizing radiation inpolyethylene. II crosslinking in chain folded single crlstals!'. Gamma rays.J.Polym.Sci. Poly.Ph)s., Ed.l3, 323, 1975.6. Spenadel.L." Radiation crosslinking of pollmer blen&". Radiation physics andchemisnyl4, 681,697, l9?9.7. Spenadel. L.,Smith. w.S.,[,fi.rthy.,J.J" Crosslink able EPDM". Rubb€r Age107.41.t97 5.L Vishu Shah"Hud book of plastic testing tecbnolosy".wiley,New York, p 79,1984.9. Wiesner.L." Eff€cts of radiation on polyethylene and other polyolefins in thepresence of oxyg€n' Radistion phlsica and chemistry 37 ,7'7 -81, 1991.10. zhang Hui. xu Jiutu." The modification ofthe fl€xibility of radiation crosslinkedPE by blending PE with EVA and CPE" Radiation physics and chenistry 42,117-l l9,  1993.t l. Jamaliah Sharif,Sharifah Hanisah Syed Abdul Abdul Aziz, Kamaruddin Hashim"Radiation effects on LDPE/EVA blends".103

Modified effects of LDPE/EVA blends by electron beam irradiation

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Modified effects of LDPE/EVA blends by electron beam irradiation

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