Melt intercalation and/or exfoliation of polystyrene-montmorillonite nanocomposites

Thermal stability of organoclays and polystyrene (PS) intercalation in organoclays by melt processing were studied. The effects of polymer viscosity, processing conditions, type of mixing and the type of fillers on the intercalation process were evaluated. The resulting nanocomposites were tested to characterize structure, thermal stability and mechanical properties.;Two new organoclays were used in this study exhibited good thermal stability. This suggested their potential use in the preparation polymer nanocomposites at high processing temperatures.;Batch mixing promoted polymer intercalation in most cases. PS nanocomposites showed a combination of intercalated and unintercalated or collapsed structures. In general, thermal stability and mechanical properties of PS were enhanced by incorporation of organoclays. Processing conditions in the batch mixer had only a small influence on intercalation behavior. However, they had a strong effect on thermal stability and mechanical properties. The degree of intercalation was dependant on the type of organoclay. As a result thermal stability and mechanical properties were influenced by the type of organoclay used. The best mechanical properties were obtained with Cloisite 10-A.;Mixing in the twin screw extruder promoted intercalation of low viscosity PS. Thermal stability was increased in all cases, but mechanical properties did not improve significantly.;The tensile modulus of nanocomposites was calculated using five models reported in the literature. The results were compared to experimental data obtained in this study. Up to 1% wt Cloisite 10-A content, the experimental results showed very good agreement with the predictions of the Halpin-Tsai and Brune models, which predicted the highest modulus values. The experimental values fell rapidly bellow theoretical predictions above 1% wt clay content.