Natural Rubber-Toughened Polystyrene: Effects of Mixing Procedure and Maleic Anhydride Content on Impact Property and Phase Morphology

Abstract

The toughening of polystyrene (PS) by melt blending with natural rubber (NR) was prepared in a brabender plasticorder. Two kinds of processing had been used: (a) one-step mixing in which the three components of PS (60 wt%), NR (40 wt%) and maleic anhydride (MA) were simultaneously introduced in the mixer; (b) two-step mixing in which NR and MA were separately premixed before the final mixing with PS. The effect of MA loading (3 and 5 phr) on gel content, impact energy and morphology of PS-NR-MA blend were further investigated. The results showed that the incorporation of NR into PS increased the impact energy of the blend. The results also showed a significant effect of the different mixing procedures on the properties of PS-NR-MA blend. High contents of unreacted MA and gel were found in the blend obtained by the one-step mixing, whereas the blend prepared by the two-step mixing showed lower values in both unreacted MA and gel content. On the other hand, the impact energy of the blend prepared by one-step mixing was slightly higher than that of the blend prepared by two-step mixing. This is due to the decreased molecular weight of NR in the formerly prepared MNR of the two-step mixing. For the effect of MA loading, the decrease of unreacted MA content, gel content and rubber particle size were found at low concentration of MA.