Role of compatibilizer and processing method on the mechanical, thermal and barrier properties of polystyrene/organoclay nanocomposites

Abstract

This study describes the role of compatibilizer i.e. styrene-maleic anhydride copolymer, its content and compounding method on the properties of polystyrene/clay nanocomposites. The nanocomposites were fabricated using three different methods: (i) simultaneous mixing of all the components i.e. polystyrene, required amounts of styrene-maleic anhydride and nanoclay using twin-screw extruder; (ii) stepwise mixing method i.e. in which blending of polystyrene and organoclay was first done using single-screw extruder and the mixed compound was then blended with varying amounts of styrene-maleic anhydride copolymer using twin-screw extruder and (iii) the effective combination of in situ polymerization of styrene-maleic anhydride copolymer in presence of varying amounts of nanoclay by free radical polymerization followed by melt mixing with polystyrene using twin-screw extruder. The effect of processing method on the micrsostructure of nanocomposites was investigated using X-ray diffraction and transmission electron microscopy. The mechanical properties of nanocomposites such as tensile, flexural and Izod impact strength were measured and discussed in relation to their microstructure. All the fabrication methods yielded nanocomposites with different microstructure ranging from intercalated to exfoliated structure of nanoclay. As expected the stepwise mixing method yielded more intercalated and exfoliated structure as compared to the simultaneous mixing method resulting in improvement in the properties of nanocomposites. On the other hand, combination of in situ polymerization with melt mixing method produced better exfoliation as compared to other two methods. Thermal stability and mechanical strength of polystyrene showed a significant improvement upon incorporation of nanoclay.