Isotactic polystyrene heat resistance

Polystyrene (PS) now on the market is atactic PS (APS), but there is a problem of low heat resistance. Isotactic PS (IPS) is also known, but there is a problem of low crystallization rate. A homogeneous Ti/metal-locene and MAO system is an effective catalyst for syndiotactic polystyrene (SPS). Advantages of SPS are heat resistance 7 110°C) and chemical resistance like engineering plastics, which are derived from its high crystallinity compared with APS produced by radical polymerization. Furthermore, the crystallization rate of SPS is faster than that of APS or IPS. 

Improvements in the performance of homopolymer GPPS through polymerization with traditional Ziegler-Natta catalysts are primarily limited to flow and glass transition temperatures. Polymerization into an isotactic backbone configuration results in a semicrystalUne structure that improves both heat and chemical resistance however, isotactic polystyrene (IPS) is slow to crystallize and therefore of little practical use with modem injection molding production techniques [3]. 

SPS is entirely different from conventional polystyrene (GPPS) in structure, physical properties, and synthetic method. The material is a new crystalline thermoplastic. Its melting point (Tm) is 270 C, the crystallization rate is very fast in comparison with isotactic polystyrene (IPS). And SPS have some superior properties such as heat resistance, chemical resistance, water/steam resistance and so on. A brief summary of these polystyrenes is given in Figure 2. 

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