Fabrication and properties of syndiotactic polystyrene/organoclay nanocomposites

Abstract

The fabrication of syndiotactic polystyrene (sPS) nanocomposite was conducted by melt intercalation method. The fabrication method proper to high temperature processing of sPS was proposed and the microstructure and thermal and mechanical properties of obtained nanocomposites were investigated. In order to avoid the thermal instability problem of organophilic clay, various amorphous styrenic polymers were introduced. By using amorphous styrenic polymers during the melt mixing process, sPS nanocomposite could be obtained successfully in both fabrication methods: step-wise mixing method and simultaneous mixing method. Amorphous polymers intercalated into the clay gallery previously was considered to play an important role in maintaining the intercalated or exfoliated structure without any contraction of interlayer spacing even at sPS melting temperature. One notable result is that the pre-melt intercalation of amorphous polymers is possible even in the simultaneous mixing method as well as the step-wise mixing method because of the great increase of diffusion coefficient at high processing temperature. The microstructures of the nanocomposites depended on the kind of amorphous styrenic polymers. Nanocomposites using poly(styrene-co-maleic anhydride) have firmer intercalation structure than those using atactic PS due to the interaction of maleic anhydride with layer surface of clay. And the exfoliated structure is obtained in nanocomposites using maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer. The improvement of mechanical properties is observed by accomplishing the nano-scaled hybrid between polymer and clay. However, there is a difference between the two fabrication methods in view of the tensile strength. The step-wise mixing method is more favorable than the simultaneous mixing method in the case of the occurrence of intercalation structure since the former method yields more complete intercalation structure. On the other hand, th...