Effect of SEBS on Impact Strength and Flexural Modulus of Polystyrene/Polypropylene Blends

Abstract

Pengadunan polistirena (PS) dengan polipropilena (PP) dibangunkan dengan objektif untuk mengatasi masalah kerapuhan PS dan meningkatkan kekuatan hentaman pada suhu bilik. Walau bagaimanapun, pengadunan PS dan PP adalah tidak serasi. Kajian terdahulu menunjukkan bahawa ko–polimer blok seperti stirena–b –(etilena–co– butilena)–b–stirena (SEBS) adalah agen penyerasi yang baik bagi adunan PS/PP ini. Kajian ini juga menyelidiki kegunaan SEBS dalam meningkatkan keserasian adunan PS/PP. Mesin penyemperit skru berkembar Brabender PL2000, digunakan untuk melakukan adunan PS/PP pelbagai komposisi dalam julat 90–60% PS yang mengandungi kandungan SEBS yang berbeza dalam julat 5–25 phr, dan diacu–suntikan bagi menentukan sifat mekanikal. Keputusan yang didapati daripada sifat mekanikal menunjukkan peningkatan sifat adunan yang menunjukkan kesan penyerasian dalam sistem adunan. Penambahan SEBS telah meningkatkan kekuatan hentaman adunan tetapi mengurangkan kekuatan dan modulus lenturan. Adunan 90/10 PS/PP dengan 25 phr SEBS menunjukkan kekuatan hentaman yang unggul. Yang menarik, keputusan menunjukkan bahawa SEBS lebih berkesan pada kandungan PP yang rendah. Kata kunci: PS; PP. SEBS; sifat mekanikal; adunan polimer Blends of Polystyrene (PS) with Polypropylene (PP) were developed with the objective to overcome the inherent brittleness of PS and enhance the impact strength at room temperature. However, the blends of PS and PP were known to be immiscible. Previous studies have concluded that the block copolymer such as styrene–b– (ethylene–co–butylenes)–b–styrene (SEBS) is good compatibiliser for this PS/PP blends. The present study investigates the use of SEBS as a compatibiliser in this immiscible blend system. Using a Brabender PL2000 twin–screw extruder, blends of PS/PP in various composition range of 90–60 wt% PS containing different amount of SEBS in the composition range of 5–25 phr were prepared and injection molded to evaluate for mechanical properties. The results obtained from mechanical properties show some improvement in the properties of the blends indicating some compatibilisation effect in the blend system. The addition of SEBS enhanced the impact properties of the blends but reduced the flexural strength and flexural modulus. The blends of 90/10 PS/PP with 25 phr SEBS gave superior impact properties. Interestingly, the results show that SEBS is more effective at lower PP content. Key words: PS; PP; SEBS; mechanical properties; polymer blends