Processing of Syndiotactic Polystyrene

DAVID bank KEVIN NICHOLS, HAROLD FOWLER, JASON REESE, and GERRY BILLOVITS  

Because of its semicrystalline nature, syndiotactic polystyrene (SPS) exhibits performance attributes that are significantly different from amorphous sty-renic materials. These properties include a high melting point, excellent hydrocarbon resistance, a high degree of dimensional stabUity, and excellent electrical performance. This combination of properties opens a wide array of potential applications. These applications are arrived at through a combination of formulation science and melt processing to enable maximum benefit from the crystalline structure of the material [1]. 

Syndiotactic Polystyrene, Edited by Jurgen Schellenberg Copyright 2010 John Wiley Sons, Inc. 

The level of crystallinity achieved following melt processing of SPS can be determined using differential scanning calorimetry. The calculated heat of fusion of 100% crystalline SPS is 53.2 J/g. Integration of the melting peak and 

Analysis of the melting behavior of SPS indicates a melting point of 270 °C. It is interesting to note that this represents one of the highest melting temperatures for a thermoplastic system that is produced from a single-monomer feedstock. Further, SPS has a glass transition temperature similar to that of atactic polystyrene measured at 100 C. 

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MELT PROCESSING OF SYNDIOTACTIC POLYSTYRENE Skin Intermediate... 

Figure 5.26 Illustration of the structural regularization process of syndiotactic polystyrene derived from Figure 5.25 [118].

With conventional polymerization processes, atactic chains are predominantly formed for the formation of isotactic and syndiotactic chains a special catalyst system is required, e.g. Ziegler-Natta catalysts. Such a process is called stereospecific polymerization. It enables the manufacture of, i.a., technically usable PP and also unbranched PE (see 4.1). The newest development is the metallocene katalyst it enables the building-up of chains-to-measure with very high degrees of chain regularity also the manufacture of syndiotactic polystyrene is technically possible in this way (see Qu. 2.47). 

Coxe, M., et al., The Establishment of a Processing Window for Thin-Wall Injection Molding of Syndiotactic Polystyrene, SPE ANTEC, 2000. 

In the present text we attempt to do justice to the different topics of polymers and their uses. This text is generally suitable for researchers rather than students. The first chapter of this book discussed sorption mechanism of organic compound in the nanopore of syndiotactic polystyrene crystal. In the second chapter, a discussion was done to illustrate a physico-chemical characterization and processing of pulse seeds. The chemo-enzymatic polymerization for peptide polymers were illustrated in the third chapter. In the fourth chapter, an electrokinetic potential method was used to characterize the surface properties of polymer foils and their modifications. Also, an emulsion polymerizations was discussed in the fifth chapter. Nonconventional methods of polymer surface patterning, polymer characterization using atomic force microscope, biopolymers in the environment, and carbon nanostructure and their properties and applications were discussed in the sixth, seventh, eighth and ninth chapters respectively. Finally, let us point that although many books in the field of pol)nner science appear, none of them are complementary. 

Finally, a few comments about the uniqueness of polymer crystal structures and phase space localization are warranted. Almost all crystallizable polymers exhibit polymorphism, the ability to form different crystal structures as a result of changes in thermodynamic conditions (e.g., temperature or pressure) or process history (e.g., crystallization conditions) [12]. Two or more polymorphs of a given polymer result when their crystal structures are nearly iso-energetic, such that small changes in thermodynamic conditions or kinetic factors cause one or another, or both, to form. Polymorphism may arise as a result of competitive conformations of the chain, as in the case of syndiotactic polystyrene, or as a result of competitive packing modes of molecules with similar conformations, as in the case of isotactic polypropylene. In some instances, the conformational change may be quite subtle isotactic polybutene, for example, exhibits... 

Pantani, R., Sorrentino, A., Speranza, V., Titomanlio, G. Morphology distribution in injection moldings of syndiotactic polystyrene. PPS-Polymer Processing Society, 18th Annual Meeting, Taipei, Taiwan, November 4-8,2002. 

Yoshioka, A., Tashiro, K. Polymer-solvent interactions in crystalline d form of syndiotactic polystyrene viewed from the solvent-exchange process in the d form and the solvent evaporation phenomenon in the thermally induced d-g phase transition. Macromolecules, 36, 3593-3600 (2003). 

Many types of commercial styrene polymerization processes are applied. However, the process for the production of syndiotactic polystyrene (SPS) is completely different from those for atactic polystyrene polymerizations. Catalysts are sensitive to the impurities in styrene monomer and SPS is insoluble in aromatic solvents. 

Cover image Scanning electron micrographs of syndiotactic polystyrene prepared by a powder bed polymerization process showing the typical cauliflower structure of the powder (SEM Dow Central Germany). 

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