Styrene-based plastics

Table 1. Mechanical Properties of Injection-Molded Specimens of Main Classes of Styrene-Based Plastics ...

Fig. 2. Stress—strain curves for styrene-based plastics.

Stress-relaxation measurements, where stress decay is measured as a function of time at a constant strain, have also been used extensively to predict the long-term behavior of styrene-based plastics (9,12). These tests have also been adapted to measurements in aggressive environments (13). Stress-relaxation measurements are further used to obtain modulus data over a wide temperature range (14). 

Injection molding of styrene-based plastics is usually carried out at 200—300°C. For ABS polymers, the upper limit may be somewhat less, because these polymers tend to yellow somewhat if too high a temperature and/or too long a residence time are imposed. 

Lamination of polymer films, both styrene-based and other polymer types, to styrene-based materials can be carried out during the extmsion process for protection or decorative purposes. For example, an acryUc film can be laminated to ABS sheet during extmsion for protection in outdoor apphcations. Multiple extmsion of styrene-based plastics with one or more other plastics has grown rapidly from the mid-1980s to the mid-1990s. 

Styrene-based plastics are used somewhat in blow mol ding but not as much as linear polyethylene and PVC. HIPS and ABS are used in specialty botdes, containers, and furniture parts. ABS is also used as one of the impact modifiers for PVC. Clear, tough bottles with good barrier properties are blow-molded from these formulations. 

In the absence of impurities there is frequently no termination step in anionic polymerisations. Hence the monomer will continue to grow until all the monomer is consumed. Under certain conditions addition of further monomer, even after an interval of several weeks, will eause the dormant polymerisation process to proceed. The process is known as living polymerisation and the products as living polymers. Of particular interest is the fact that the follow-up monomer may be of a different species and this enables block copolymers to be produced. This technique is important with certain types of thermoplastic elastomer and some rather specialised styrene-based plastics. 

In addition to polystyrene and high-impact polystyrene there are other important styrene-based plastics. Most important of these is ABS, with a global capacity of about 5 X 10 t.p.a. and production of about 3 X 10 t.p.a. The styrenic PPO materials reviewed in Chapter 21 have capaeity and production figures about one-tenth those for ABS. Data for the more specialised styrene-acrylonitrile copolymers are difficult to obtain but consumption estimates for Western Europe in the early 1990s were a little over 60000 t.p.a. 

Some typical properties of styrene-acrylonitrile plastics, referred to in many countries as SAN, are compared with those of other styrene-based plastics in Table 16.7. 

Styrene maleic anhydride SMA is a copolymer made with or without rubber modifiers. They are sometimes alloyed with ABS and offer good heat resistance, high impact strength and gloss but with little appreciable improvement in weatherability or chemical resistance over other styrene based plastics. 

Dynamic differential thermal analysis is used to measure the phase transitions of the polymer. IR is used to determine the degree of unsaturation in the polymer. Monitoring of the purity and raw is done commercially using gas phase chromatography for fractionization and R1 with UV absorption at 260 nanometers for polystyrene identification and measurement Polystyrene is one of the most widely used plastics because of fabrication ease and the wide spectrum of properties possible. Industries using styrene-based plastics are packaging, appliance, construction, automotive, radio and television, furniture, toy, houseware and baggage. Styrene is also used by the military as a binder in expls and rocket propints... 

Impact strength (impact resistance), 10 177 of polycarbonates, 19 810-811 of styrene-based plastics, 23 362-363 Impact testing, 19 580 Impact tests, for polymer blends, 20 352... 

Stress-relaxation measurements of styrene-based plastics, 23 362 on tempering, 23 285-286... 

Styrene-based copolymers, 10 171 orientation of, 23 399 Styrene-based plastics. See also Styrene plastics... 

Svec, P., et al., Styrene-based Plastics and Their Modification, Ellis Horwood, New York (1989). 

Styrene is one of the most important aromatic monomers used for the manufacture of plastics. Small-scale commercial production of styrene began in the 1930s. Demand for styrene-based plastics has grown significantly, and in 2003 the worldwide annual production capacity was approximately 24.5 million metric tons. ... 

Table 16.12 Production and consumption breakdown for main types of styrene-based plastics in the late 1990s...

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