Characteristics of Impact Modified Polystyrene/Organoclay Nanocomposites

The poor impact resistance of Polystyrene (PS) was enhanced by the addition of elastomeric material, SEBS-g-MA. To prevent the reduction in strength and stiffness, organoclay Cloisite (R) 25A was used as filler and introduced into the matrix by a corotating twin screw extruder. Throughout the study, the clay content was kept at 2 wt%, whereas the content of SEBS-g-MA was varied between 5 and 40 wt%. It was found that Cloisite (R) 25A displays well dispersion in the ternary nanocomposites and the degree of dispersion increases with the elastomer content. The elastomeric phase has a greater viscosity than pure PS. Thus, as expected, at low elastomer contents, it forms the dispersed phase in the matrix as droplets. Transmission electron microscopy results show that the clay layers reside at the interphase between PS and elastomer and also inside the elastomeric phase. Owing to the location of the clay particles, the average elastomer domain size in ternary nanocomposites are found to be greater than that in the relative binary blends of PS(SEBS-g-MA). Moreover, with the organoclay addition, phase inversion point shifts to lower elastomer contents. The mechanical test results showed that the nanocomposites containing 15 and 20 wt% SEBS-g-MA have the optimum average domain size that results in high-impact strength values without deteriorating the tensile properties. POLYM. COMPOS., 31:1853-1861, 2010. (C) 2010 Society of Plastics Engineers