Toughened polystyrene

Poly(phenylene sulphide) Polypropylene Polystyrene toughened with rubber Styrene-acrylonitrile... 

Synonyms High-impact polystyrene HIPS Polystyrene, toughened... 

Figure 13 Attenuation plots for a variety of polymer systems as a function of temperature (a) poly(phenylene sulfide) (b) poly(ether sulfone) (c) polyester DMC (d) copoly(acrylonitrile/styrene/acrylate) (e) poly(acrylonitrile/butadiene/styrene) (f) polystyrene (toughened) (g) polyester resin (h) melamine formaldehyde (i) polyimide (j) ekonol (k) nylon 6 (1) poly-(phenylene oxide) (m) polypropylene (n) phenol formaldehyde (o) poly(vinyl chloride) (rigid) (p) poly(vinyl chloride)...

Cheap moulded objects. Toughened with butadiene to moke high-impact polystyrene (FIIPS). Foamed with CO2 to moke common packaging. 

In addition to the high-impact (toughened) polystyrenes dealt with later in this chapter, polystyrene is available in a number of grades. These may conveniently be grouped as follows ... 

High-impact Polystyrenes (HIPS) (Toughened Polystyrenes (TPS)) 437... 

HIGH-IMPACT POLYSTYRENE (HIPS) (TOUGHENED POLYSTYRENES (TPS))... 

Transparent toughened polystyrene polymers are produced by blending polystyrene with SBS block copolymers (see Section 11.8). During the 1970s and 1980s most development was with block copolymers with a radial (or star) shape. Two types were developed block copolymers with a central butadiene block, and block copolymers with a central polystyrene block. 

The largest outlet for polystyrene is in packaging applications. Specific uses include bottle caps, small jars and other injection moulded containers, blown containers (a somewhat recent development but which has found rapid acceptance for talcum powder), vacuum formed toughened polystyrene as liners for boxed goods and oriented polystyrene film for foodstuffs such as creamed... 

Polycarbonate-polystyrene blend along with poly(alkylene-dicarboxylate) such as SMA SEBS copolymer for toughening blends of PPO with nylon and polyolefin (proprietary compatibilizer)... 

We have considerable latitude when it comes to choosing the chemical composition of rubber toughened polystyrene. Suitable unsaturated rubbers include styrene-butadiene copolymers, cis 1,4 polybutadiene, and ethylene-propylene-diene copolymers. Acrylonitrile-butadiene-styrene is a more complex type of block copolymer. It is made by swelling polybutadiene with styrene and acrylonitrile, then initiating copolymerization. This typically takes place in an emulsion polymerization process. 

We most often encounter polystyrene in one of three forms, each of which displays characteristic properties. In its pure solid state, polystyrene is a hard, brittle material. When toughened with rubber particles, it can absorb significant mechanical energy prior to failure. Lastly, in its foamed state, it is versatile, light weight thermal insulator. 

One of the principal weaknesses of pure polystyrene is its low impact resistance. To counteract this problem, we toughen it with various types of rubber. This is most effective when a portion of the rubber is chemically grafted to the polystyrene. The rubber forms small inclusions within a matrix of polystyrene. The presence of rubber also improves polystyrene s extensibility, ductility, and resistance to environmental stress cracking. 

Rubber toughened polystyrene is widely used in electronic and kitchen appliances. This type of application requires a good balance of stiffness, impact resistance, and ready coloration. Telephones, which are frequently dropped, are an excellent example of the benefits of rubber toughened polystyrene. The high surface gloss that we desire is obtained by minimizing the size of the rubber particles. Larger items, such as canoes, can be thermoformed from extruded sheet. 

An important class of copolymers made by chain copolymerisation is graft copolymers, synthesized in order to toughen brittle materials through inclusion of a rubber phase. Examples are the cases of styrenic copolymers called "HIPS" for High-Impact Polystyrene and ABS for Acrylonitrile-Butadiene-Styrene. Both are synthesized in two steps. 

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