Styrenic plastics chemical structure

This chapter on styrenic plastics covers a hroad class of polymeric materials of which an important part is styrene. Styrene, also known as vinyl benzene, is an organic compound with the chemical formula C6H5CH=CH2- Its structure is shown in Figure 2.1. 

ABS plastics are derived from acrylonitrile, butadiene, and styrene with the following general chemical structure ... 

Phenylene oxide Based (PPO) plastic that is a choice for electrical applications, housings for computers and appliances, both neat and in structural foam form. It has superior dimensional stability, moisture resistance due to styrene components, which, however, cause some sacrifice of weather and chemical resistance. Use includes automobile wheel covers, pool plumbing, consumer electronic external and internal components. 

In his famous work of 1920 Hermann Staudinger first described the correct structure of polystyrene (10). It was Staudinger, too, who gave polystyrene its name and elucidated the mechanism of its formation (11). The polymerization of styrene provided access to a big class of substances and made a significant contribution to the understanding of natural polymers and to the synthesis of industrial plastics. A whole new branch of the chemical industry is based on the key substance polystyrene. 

Acrylonitrile resembles VC, a carcinogen, in structure. It is a flammable, explosive liquid (b.p. 77 C, V.P. 80 mm at 20°C). AN is a component of acrylic and modacrylic fibers produced by copolymerization with other monomers, e.g., with methyl acrylate, Me-methacrylate, vinyl acetate, VC and VDC. Other major uses of AN include copolymerizations with butadiene and styrene to produce ABS polymers, and with styrene to yield SAN resins which are used in the manufacture of plastics. Nitrile elastomers and latexes are also made with AN, as are a number of other chemicals, e.g. acrylamide and adiponitrile. Acrylonitrile is also used as a fumigant. 

Characteristic functions and the representative structures of plastics additives providing marketable and durable materials are included in this chapter. Types of additives for plastics used in contact with food are listed in Table 3-1. Similar additives as for PS are used for elastomer-modified plastics forming multilayer systems (blends) and used rather exceptionally in contact with food, such as high-impact polystyrene (HIPS) or acrylonitrile-butadiene-styrene polymer (ABS). Some of the additives, stabilizers in particular, are very reactive and are present in the plastic matrix in a chemically transformed form. 

Synthetic polymers in general can be classified (1) by thermal behavior, i.e., thermoplastic and thermosetting (2) by chemical nature, i.e., amino, alkyd, acrylic, vinyl, phenolic, cellulosic, epoxy, urethane, siloxane, etc. and (3) by molecular structure, i.e., atactic, stereospecific, linear, cross-linked, block, graft, ladder, etc. Copolymers are products made by combining two or more polymers in one reaction (styrene-butadiene). See cross-linking block polymer epitaxy homopolymer plastics. 

The polymers described in this chapter are industrial-grade materials, and consequently some of the examples may contain additives and/or may be chemically modified. Polymers in various morphological forms may be analyzed, and these include films, fibers, solid pelletized and powdered products, and dissolved/dispersed materials in liquids such as paints and latex products. Also, the same base polymer, such as a styrene-butadiene copolymer, for example, may exist in a rubber, a resin, or a plastic. In general, reference will not be made to the original source of the polymer samples. Because infrared spectroscopy is more widely used than the Raman method, the authors will focus more on the applications of this technique. However, the Raman method, which is complementary to the IR method, does have important and unique applications in the polymer analysis, especially with regard to the determination of the fundamental polymer structure and its... 

Furthermore, the C=C bonds in the natural rubber structure might induce poor thermal and oxidative resistance in the natural rubber blends. Thus, Thawornwisit and coworkersproposed the preparation of hydrogenated natural rubber, which is one of the chemical modifications available to improve the oxidation and thermal resistance of diene-based natural rubber before blending with poly(methyl methacrylate-co-styrene). The poly(methyl methacrylate-co-styrene) was resistant to the outdoor environment and had excellent optical properties with a high refractive index, but it was extremely brittle and had low impact strength. Hydrogenated natural rubber could, however, be used as an impact modifier, as well as to improve its thermal and oxidative resistance for these acrylic plastics. 

Other plastics are used in plant structures, although less extensively. Among these are the acrylonitrile butadiene styrene (ABS) resins, the polyvinyl fluoride resins, the polycarbonate resins, and the polyurethanes. The epoxy resins have been used extensively in structural apph-cations (such as flooring) and adhesives. Specialized apphcations include use in chemically resistant coatings and in plasters for exposed aggregate wall finishes. 

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