Polystyrene clear impact resistant

Clear impact-resistant polystyrene is a commercial plastic with the desirable combination of toughness and exceptional clarity. It is a styrene-1,3-butadiene multiblock copolymer containing more than 60% styrene. Most of these products are mixtures of block copolymers formed by incremental additions of initiator and monomers followed by coupling (Sec. 5-4c). The products generally have a tapered and multiblock composition with branching (due to the coupling agent). 

The annual worlwide production of triblock thermoplastic elastomers, clear impact-resistant polystyrene, and other styrene-diene products produced by anionic polymerization exceeds a couple of billion pounds. (Commercial utilization of anionic polymerization also includes the polymerization of 1,3-butadiene alone.)... 

K-Resin BDS Polymer A New Clear Impact-Resistant Polystyrene... 

Triblock polymers and radial block polymers of styrene and butadiene (or isoprene) are successful commercial thermoplastic elastomers pioneered by the Shell Chemical Company and the Phillips Petroleum Company. The low diene and high styrene block polymers are clear impact resisting plastics marketed by the Phillips Petroleum Company under the trade name K-Resins. One common deficiency of these polymers is the relatively low glass temperature (Tg) of the polystyrene end blocks. For the thermoplastic elastomers the service temperatures are limited to below 65°C. The Vicat softening... 

Styrene—acrylonitrile (SAN) copolymers [9003-54-7] have superior properties to polystyrene in the areas of toughness, rigidity, and chemical and thermal resistance (2), and, consequendy, many commercial appHcations for them have developed. These optically clear materials containing between 15 and 35% AN can be readily processed by extmsion and injection mol ding, but they lack real impact resistance. 

An important result of such studies was the realization that almost all commercially important polymer blends, blocks, and grafts clearly exhibit phase separation, and that each has its own characteristic fine structure. An example of a typical morphology for an impact-resistant plastic is shown in Figure 2.4. Although the polymer contains only 6% rubber, much of the volume of polystyrene is occluded (Wagner and Robeson, 1970). Those interested in the details of electron microscope construction and operation, as well as experimental techniques, should consult Hall (1966) or Kay (1965). 

While the impact resistance of the mechanical blends is clearly superior to that of the parent polystyrene, they have two important deficiencies that cause them to be inefficient. First, due to the high viscosity of the melts, the problem of attaining intimate mixing cannot be entirely overcome. As a result, the dispersed phase maintains a relatively large particle size, as shown in Figure 3.1. Second, the two phases are bonded together only by weak van der Waals forces, so that the material as a whole exhibits poor cohesion. 

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