Miscibility and Mechanical Properties of High-Impact Polystyrene Blended with Poly(α-olefin) Grease

Abstract

Small amount of impurities or contaminations in recycled plastic have a possibility to influence on mechanical properties of product. In this study, miscibility and mechanical properties of melt-blended high-impact polystyrene (HIPS) and poly(a-olefin) (PO)-based grease have been investigated. We have focused attention on the molecular weight (M w ) of PO, and the range of M w for PO in the used greases was 690-8,500. Changes of glass transition temperature were observed for polystyrene and polybutadiene phases in the HIPS/grease blends, that indicated small amount of PO was solubilized into HIPS. When M w of PO was higher than 5,000, insoluble excess PO acted as lubricant, and sample preparation was difficult since slipping between the polymer and chamber wall or screw occurred during melt blending. By this limitation in solubility of HIPS/grease, depression of mechanical properties such as flexural modulus and strength for the obtained blends was not remarkable. On the other hand, blends with high grease content could be obtained for PO with low M w because of its good solubility with HIPS, as the result, their flexural properties were highly deteriorated than the original HIPS. Therefore, the grease containing high molecular weight PO has a smaller influence on the mechanical properties of HIPS/grease because of the limitation in solubility. Results of chemical stress crack tests for HIPS/grease were also explained by the miscibility of PO with HIPS.