The effects of glass powder on some mechanical properties of engineering thermoplastics

Transcription

1 J. Natn.Sci Fundatin Sri Lanka (1): The effects f glass pwder n sme mechanical prperties f engineering thermplastics L.Karunanayake Department f Chemistry, University f Sri Jayewardenepura, Gangdawila, Nugegda, Revised: 13 March 2006 ; Accepted: 20 December 2006 Abstract: The manufacture f cmpsite materials based n plastics using fillers such as glass fibre, carbn black and wd dust is dne t impart better prperties r/and t reduce the cst f material. In this study, glass pwder was used as a filler in fur engineering plastics, namely, Nyln 6, Nyln 66, Plybutylene terephthalate and Plyarylamide. Mixing f glass pwder and plymers was achieved by melt blending using a twin-screw extruder. Prperties such as tensile prperties, flexural prperties, muld shrinkage, thermal expansin and specific gravity were ascertained using injectin-mulded samples. It was fund that glass pwder can be mixed effectively with the abve fur plastics. The desirable effects f mixing f glass pwder with the fur thermplastics was evident by the significant imprvement f sme prperties. The cmpsites f plyarylamide shwed mre desirable prperties indicating high cmpatibility. Keywrds: Blending, engineering plastics, glass pwder, physical prperties, plymer cmpsites. INTRODUCTION The incrpratin f glass fibre in plymeric materials t enhance prperties f end prducts has been well-studied 17. Sme f the plymer glass fibre cmpsites that have been studied cntain a wide range f plymers such as Nyln 6 (PA6) 16, Plybutylene terephthalate () 1, Plyprpylene 3 and Epxy resins 7. Glass fibre reinfrced plymer nancmpsites have als been recrded. Hwever, the use f glass pwders in plymer cmpsites is less cmmn. Fillers such as glass fibre imprves prperties f thermplastics like falling weight impact strength 5, cmpressive strength 8, albeit with sme adverse effects, fr example increase in density, decrease in melt flw and increase in brittleness 6. Further, the incrpratin f glass fibres t engineering plastics is fund t be essential in semi-structural applicatins t imprve strength, stiffness and fatigue resistance 1. Scientists 1 have reprted that when glass fibres are used as fillers, sme prperties f the material depend significantly n the rientatin f fibres, which in turn depends n, flw directin, gemetrical feature f the muld and psitins f gates. Althugh, the abve factrs can affect the distributin f glass pwders that are used in this study, the prblem f rientatin f the glass fibre becmes a trivial factr. Further, veryfinepwder like glass beads have been used in applicatins such as dental fillings 8 and prsthetic fixatin r as a bne substitute in rthpaedics, 9 where the penetratin f materials t very fine cavities and the strengthening f the plymeric material are imprtant. Glass pwder has significant advantages ver glass fibres. In sme studies, the suggested glass pwder level is as high as 70% (w/w) and this has been achieved by activating the surface f glass pwders using silane-cupling agents 9. Hwever, these bilgical applicatins d nt need the type f high physical prperties that applicatins f engineering plastics demand. The bjective f this investigatin was t study the effects f incrpratin f glass pwders n the prperties f fur engineering thermplastics at fur different lading levels. The prperties f fur thermplastic cmpsites with different glass pwder levels were measured. Since glass pwder is a material that can be prducedfrmwaste r scrap glass, it can be treated as an inexpensive material that can be used with different plastics. METHODS AND MATERIALS The glass pwder used in this study was f im average particle size and 2.5 specific gravity.

2 14 L Karunanayake Table 1: Temperature settings fr the injectin mulding machine Material Barrel Rear/ C Barrel/ C Barrel Middle / C Barrel Frnt/ C Nzzle/ C Muld/ C PA PA A Fur engineering plastics Nyln 6 (), Nyln 66 (6\ Plybutylene terephthalate () and Plyarylamide () were blended with different amunts f glass pwders using a Brabender twin-screw extruder. The barrel temperatures used fr the extruder are similar t the barrel temperatures f the injectinmulding machine (see Table 1). The feeding speed was kept at rpm. Samples cntaining 15%, 30% and % (w/w) glass pwder were prepared fr each plymer by mixing them in a plyethylene bag. The ttal weight f the sample was kept at 2 kg. A 2 kg sample f each virgin plymer was taken as the cntrl. Befre charging the extruder fr melt blending, all samples were dried vernight at 100 C in an air-circulating ven. Feeding the hpper was dne very carefully t minimize bridge frmatin in the metering area. Special attentin was required during the extrusin f highly laded plymers (i.e. %). The extruded plymer strands were cled using a water bath and subsequently granulated using a granulatr. The granules btained were dried fr 12 h in an air circulating ven perating at 100 C t remve the absrbed water. Test specimens were injectin mulded t determine flexural prperties 10, Izd impact strength 11, tensile prperties l2, density l3, cefficient f linear thermal expansin 14 and mulding shrinkage 15. The injectin mulding machine was prgrammed t btain temperature settings given in Table 1. Dimensins f test specimens prepared were in accrdance with crrespnding ISO standards. All the abve tests were dne accrding t the ISO standards. RESULTS The results f the prperties measured are presented as a rati t facilitate the fllwing. 1. Cmparisn f effects f glass pwder cntent n the prperties f individual plymers. 2. Cmparisn f effects f glass pwder filling n the prperties f fur plymers. The rati is calculated using the fllwing equatin. Prperty rati = DISCUSSION Value f the actual Prperty Value f the Prperty fr the virgin plymer The separatin f high-density glass pwder frm the lw-density plastic pellets was encuntered during the feeding f the materials fr melt mixing in the extruder. This was very significant with higher filler ladings and special attentin was given t ensure that the feed t the hpper f the extruder was as hmgeneus as pssible. Further, it was bserved that the frmatin f bridges by the fine glass pwder blcks the metering area when the hmgeneity f mixture was pr. This results in very shrt strands f the plymer making cntinuus prcess f granulatin impssible. Accrding t Figure 1, it is clear that the muld shrinkage decreases with the increase f glass pwder cntent. The highest decrease was bserved fr the and the lwest decrease was recrded fr PA66. This shws that the incrpratin f glass pwder in engineering plastics can significantly reduce the muld shrinkage Figure 1: Effect f filler cntent n muld shrinkage K - March 2007 Jurnal f the Natinal Science Fundatin f Sri Lanka 35(1)

3 Effects f glass pwder n engineering thermplastics 15 In Figure 2, althugh the plymer shws a remarkable increase in Izd ntched impact strength with the increase f glass pwder cntent, the ther three plymers shw steady decrease shwing very similar patterns. The latter is t be expected as the brittleness f die filled samples are fund t increase with the filler cntent and the resistance t crack prpagatin decreased 4,6, althugh the frmer is unexpected. That can be due t the fact that the incrpratin f glass filler t has imparted a resistance t crack prpagatin i75 1.? ^ jj 0. Figure 4: Effect f filler cntent n tensile strength j A -* g 0. a E 6 Figure 2: Effect f filler cntent n impact strength (Izd-ntched) Figure 3 shws a much larger variatin f Izd unntched impact strength values, and cnfirms the pattern shwn by and the ther three plymers seen in Figure 2. The increase in impact strength values f with the increase f filler cntent can be attributed t increase in interfacial adhesin between the plymer and the glass filler 3. It shws that the glass pwder is mre cmpatible with than the ther three plymers. On the ther hand, the decrease in unntched Izd impact strength is nrmal fr plymers with less cmpatibility with glass pwder as the fracture tughness is reduced due t the incrpratin f glass pwder 6. virgin samples althugh there is n linearity in the decrease, as well. These results als cnfirm the findings f impact strength experiments. Scientists 3 have attributed the increase f mechanical prperties f their blends f glass fibre reinfrced nyln 6/ prpylene blends t enhancement f stress transfer. Therefre, the enhancement f mechanical prperties such as impact strength and tensile strength in glass pwder enriched samples can be due t strng interactin and adhesin between the tw materials. As depicted in the Figure 5, the elngatins at break values recrded are lwer than thse f crrespnding virgin plymers, except in the case f 15% (w/w) filled sample. Hwever, less reductin f elngatin at break values f samples is nticeable. This clearly supprts the abve argument. A previus study 6 has attributed the reductin f tughness t the presence f rigid particles in the cmpsites. Mrever, the reductin f tughness is the cause fr the reductin f ultimate elngatin. _ E 2.00, CO * i Figure 3: Effect f filler cntent n impact strength (Tzd-unntched) Accrding t the tensile values illustrated in Figure 4, althugh there is n linearity f increase, the incrpratin f the filler has increased the tensile values remarkably fr cmpsites f. The tensile strength values f the ther three plymers have decreased with the incrpratin f glass pwder cmpared t that f their Figure 5: Effect f filler cntent n elngatin at break As in the prperties discussed earlier, flexural strength values f sample illustrated in the Figure 6 have shwn a clear increase. Hwever, in cntrast t the earlier results, PA6 has als shwn an increase f values with increase f filler cntent after an initial set back. PA66 has shwn decrease with filler cntent while values fr have shwn an irregular pattern. This is in accrdance with the argument f scientists' where they have claimed that flexural and tensile results can shw Jurnal f the Natinal Science Fundatin f Sri Lanka 35(1) March 2007

4 16 L. Karunanayake significant differences due t the methd f measuring tsuring the flexural strength ( f 1.10 & I 0. Figure 6: Effect f filler cntent n flexural strength 6 Figure 7 illustrates that the samples f and PA6 shw a steady increase in flexural mdulus values with the increase f glass pwder cntent where as the samples f and PA66 shw a lesser increase. As the decrease in flexural mdulus is anticipated with the increase f impact strengths 5, the decrease f flexural mdulus f with the increase f filler cntent is desirable. Hwever, it is remarkable that this decrease is very similar t that f PA66, which shws much lwer impact strength values with the filler ladings I Figure 7: Effect f filler cntent n flexural mdulus 6 Cmpsites f, PA6 and have shwn cnsiderably lw values f thermal expansin cefficient cmpared t their virgin materials (Figure 8). These values reduce with the increase f glass pwder cntent incrprated. The lwest values are fund t be fr the samples made with. The curves, which are very clse t each ther, that illustrate increases f specific gravity values with glass filler cntent seen in Figure 9 prvide the evidence f hmgeneity and effectiveness f mixing glass pwder t plastics. Hwever, the increase f specific gravity f plastics has been treated as a significant drawback in incrpratin f glass fillers t plastics 6. % w at Figure 8: Effect f filler cntent n linear thermal expansin.2 (0 \-> +- > t_ O 2L cefficient (LTEC) Figure 9: Effect f filler cntent n specific gravity CONCLUSION 6 The significant prperty changes that ccurrs, in particular the changes f specific gravity, due t the incrpratin f glass pwder have prvided evidence fr successful mixing f glass pwder t PA6, PA66, and. Further, it was fund that the plymer is highly cmpatible with glass pwder. This cmpatibility has imparted imprvements in prperties such as muld shrinkage, impact strength, tensile prperties and thermal expansin. All fur plymers have shwn imprvement in muld shrinkage, albeit they have shwn increase in density, which is a disadvantage, when mixed with glass pwder. Acknwledgement The Schl f Plymer, University f Nrth Lndn, Lndn, where the authr carried ut initial wrk f this prject is acknwledged. References 1. Wyzgski M.G., Krhn J.A. & Nvak G.E. (2004). Fatigue f fibre-reinfrced injectin mulded plastics. I: stresslifetime data. Plymer Cmpsites 25(5): Pegretti A., Fambri L. & Migliaresi C. (2000). Interfacial stress transfer in nyln-6/e-glass micrcmpsites: effect f temperature and strain rate. Plymer Cmpsites 21(3): March 2007 Jurnal f the Natinal Science Fundatin f Sri Lanka 35(1)

5 Effects f glass pwder n engineering thermplastics 17 3 Abbacha N & Fellahi S (2002) Synthesis f PP-g-MAH and evaluatin f its effect n the prperties f glass fibre reinfrced nyln 6/ prpylene blends Macrmleeulai Sympsia Gabbert J D, Garner A Y & Hednck R M (1983) Reinfrced nyln 6 blck cplymers Plymer Cmpsites 4(3) Mascia L & Kmsella M (1993) Thermplastics cmpsites with ductile fibre catings based n UHMWPE A study n shrt fibre GR nyln 6 Plymer Cmpsites 14(2) Akkapeddi M K (2000) Glass fibre reinfrced plymer nancmpsites Plymer Cmpsites 21(4) Mehlenpah A E, lshai O & Dibenedett AT (1971) The effect f time and temperature n the mechanical behavir f epxy cmpsites Plymer Engineering and Science 11(2) Akinmade A O, Braybrk J H & Nichlsn J W (1994) Glass plyalkenate dental cements based n physical blends f ply(acryhc acid) and ply(vinyl phsphnic acid) Plymer Internatinal 34(1) Shinzat S, Nakamura T, Kkub T & Kitamura Y (2002) PMMA based biactive cement Effect f glass bead filler cntent and histlgical change with time Jurnal f Bimedical Materials Research Internatinal Organizatin fr Standardizatin (2001) Plastics - Determinatin f exural prperties ISO Internatinal Organizatin fr Standardizatin (2000) Plastics - Determinatin f Izd impact strength ISO Internatinal Organizatin fr Standardizatin (1993) Plastics - Determinatin f tensile prperties ISO Internatinal Organizatin fr Standardizatin (2004) Plastics - Methd fr determining the density f nn-cellular plastics ISO Internatinal Organizatin fr Standardizatin (1999) Plastics - Thermmechanical analysis (TMA) Part 2 Determinatin f cefficient f linear thermal expansin and glass transitin temperature ISO Internatinal Organizatin fr Standardizatin (2001) Plastics Injectin mulding f test specimens f thermplastic materials Part 4 Determinatin f mulding shrinkage ISO Jurnal f the Natinal Science Fundatin f Sri Lanka 35(1) March 2007