Impact polystyrene synthesis

There are few results in the literature on the evolution of transformation diagrams during chain reactions of thermosets. From a thermodynamic point of view, before the gel point the behavior is similar to the well-studied synthesis of high-impact polystyrene (Bucknall, 1989). But after the gel point, which arrives at low conversions, the contribution of elastic forces to the free energy of mixing has to be added in Eq. (8.1) (De Gennes, 1979). 

Styrene and butadiene also form copolymers known as high impact polystyrene, or rubber-modified polystyrene, when the content of butadiene is 10%. This type of material has excellent mechanical properties, and it is widely used in practice for the manufacturing of numerous objects, including parts for household appliances, furniture, etc. Rubber-modified polystyrene is commonly used as wood replacement and also for packaging. The synthesis of this material typically is done by dissolving polybutadiene in styrene monomer, followed by free radical polymerization achieved using a peroxide catalyst. This procedure leads to block or graft type copolymers. 

Li, D. Peng, J. Zhai, M. Qiao, J. Zhang, X. Wei, G., Novel Methods for Synthesis of High-Impact Polystyrene with Bimodal Distribution of Rubber Particle Size. J. Appl. Polym. Sci. 2008,109, 2071-2075. 

Another type of linear flow reactor system for the synthesis of high-impact polystyrene is shown in Fig. 5 [1]. Here, the first-stage backmixed reactor (CSTR) is maintained just beyond the phase-inversion point (98 C, 14% solids) and the dissolved styrene reacts to form either a graft copolymer with the rubber or a homopolymer in the linear flow reactor train. Note that a portion of the effluent (130°C, 35% solids) from the second reactor is recycled to the first reactor. The temperature of the polymerizing mixture is gradually increased as it travels through the linear flow reactors and the final conversion of about 72% is achieved. 

Copolymerization allows the synthesis of an almost unlimited number of different products by variations in the nature and relative amounts of the two monomer units in the copolymer product. A prime example of the versatility of the copolymerization process is the case of polystyrene. More than 11 billion pounds per year of polystyrene products are produced annually in the United States. Only about one-third of the total is styrene homopolymer. Polystyrene is a brittle plastic with low impact strength and low solvent resistance (Sec. 3-14b). Copolymerization as well as blending greatly increase the usefulness of polystyrene. Styrene copolymers and blends of copolymers are useful not only as plastics but also as elastomers. Thus copolymerization of styrene with acrylonitrile leads to increased impact and solvent resistance, while copolymerization with 1,3-butadiene leads to elastomeric properties. Combinations of styrene, acrylonitrile, and 1,3-butadiene improve all three properties simultaneously. This and other technological applications of copolymerization are discussed further in Sec. 6-8. 

MacDonald AA, Dewitt SH, Ghosh S, Elogan EM, Kieras L, Czarnik AW, Ramage R, The impact of polystyrene resins in solid-phase organic synthesis, Mol. Diversity, 1 183-186, 1996. 

An easy recovery of a catalyst from a mixture of reagents/products as well as its simple handling and recycling are important problems in chemical synthesis. Consequently, new recoverable catalysts attract increasing attention and the use of polymeric supports became a common practice. Polystyrene [1] is one of the most popular polymer supports due to its availability, facile functionalization and chemical inertness. However, such organic polymers usually show a solvent swelling dependent performance, which impacts the catalytic activity of the supported species. Polysiloxanes, due to unusually high flexibility of the polymer chain and low barrier... 

N. Devia-Manjarres, G. Yenwo, J. Pulido, J. A. Manson, A. Conde, and L. H. Sperling, Castor Oil Based Interpenetrating Polymer Networks Synthesis and Properties of Emulsion-Polymerized Products, AIChE Symp. Ser. 73(170), 133 (1977). Sulfur-vul-canized/polystyrene IPN. Impact resistance. Sodium ricinoleate as emulsifying agent for polymerization of polystyrene. 

---