Rubber-toughened transparent

There is always a concern when one tries to optimize properties such as transparency and toughness, because the requirements for those two in terms of particle size conflict with each other. For example, rubber-toughened ABS is opaque because the particle size of the rubber particles is kept at 1 /am in order to optimize toughness. 

Polystyrene may be extruded to produce film and other transparent articles with high gloss finish but in commercial practice the formulations toughened with rubber are used to a greater extent (extruded transparent film is toughened by stretching and orientation while it is still hot from the die). 

Two families of transparent polycarbonate-silicone multiblock polymers based on the polycarbonates of bisphenol acetone (BPA) and bisphenol fluorenone (BPF) were synthesized. Incorporation of a 25% silicone block in BPA polycarbonate lowers by 100°C the ductile-brittle transition temperature of notched specimens at all strain rates silicone block incorporation also converts BPF polycarbonate into a ductile plastic. At the ductile-brittle transition two competing failure modes are balanced—shear yielding and craze fracture. The yield stress in each family decreases with silicone content. The ability of rubber to sustain hydrostatic stress appears responsible for the fact that craze resistance is not lowered in proportion to shear resistance. Thus, the shear biasing effects of rubber domains should be a general toughening mechanism applicable to many plastics. 

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