An investigation of recycled expanded polystyrene/polybutadiene blends

In this paper we studied the mechanical, rheological and morphological properties of recycled expanded polystyrene/polybutadiene (rPS/PB) blends. Mechanical properties including tensile strength, impact strength and Durometer hardness were investigated as a function of PB content. A differential scanning calorimeter (DSC) was used to determine the glass transition temperature and heat flow associated with material transition. Rheological and morphological behaviour of rPS/PB blends was studied using a capillary rheometer and scanning electron microscopy (SEM). Viscosity was investigated in terms of the effects of shear rate and content of PB. The shear viscosity of blends was measured at 473, 483 and 493 K with shear rates from 50 s(-1) to 400 s(-1). The activation energy of flow was also estimated. The compositions of the rPS/PB blends were 98/2, 95/5 and 90/10. The results showed that the properties of brittle recycled PS could be changed by introducing a ductile polymer such as PB. The ductility of recycled PS/PB blends was improved when PB content was higher than 2 wt%, which showed significant increase in elongation at break and impact strength. The tensile strength and hardness decreased with increasing PB content. The heat flow at the glass transition decreased with increasing the content of PB. The changes in the glass transition temperature for rPS/PB blends were statistically insignificant in the range of PB content considered in this study. The viscosity of the blends decreased with an increase in shear rate and increased with increasing the content of PB. The activation energy of flow increased with increasing PB concentration. Negative deviation from the rule of mixtures and poor homogeneity of blends were related to viscosity ratio of rPS/PB systems and injection moulding process.