Polymers grafted-rubber reinforced

ABS and HIPS. The yield stress vs. W/t curves of ABS and HIPS are very similar. They are somewhat surprising because the yield stresses reach their respective maximum values near the W/t (or W/b) where plane strain predominates. This behavior is not predicted by either the von Mises-type or the Tresca-type yield criteria. This also appears to be typical of grafted-rubber reinforced polymer systems. A plausible explanation is that the rubber particles have created stress concentrations and constraints in such a way that even in very narrow specimens plane strain (or some stress state approaching it) already exists around these particles. Consequently, when plane strain is imposed on the specimen as a whole, these local stress state are not significantly affected. This may account for the similarity in the appearance of fracture surface electron micrographs (Figures 13a, 13b, 14a, and 14b), but the yield stress variation is still unexplained. 

Since these rubber particles are highly filled with a homopolymer or a copolymer, the rubber is already reinforced with a resin to give a higher modulus particle than the grafted rubber latex. On the basis of the uniqueness of these rubber particles, this process is also more appropriate in manufacturing high-strength medium-impact ABS polymer (31), or rubber-reinforced styrene-methyl methacrylate copolymer (32). The... 

This type of graft copolymerization has been applied to the grafting of monomers like styrene and methyl methacrylate to natural rubber [271], directly in the latex [272,273]. Similar methods have been developed for grafting the foregoing monomers, and many other vinyl monomers, to synthetic rubbers like SBR, leading to a variety of plastic-reinforced elastomers and rubber-reinforced high-impact plastics [270,274]. In this case, grafting can also occur by the copolymerization of the monomer with the unsaturated bonds (mainly vinyl) in the polymer as described previously [see Eq. (96)] thus... 

For the ensuing discussion of mechanical reinforcement effects it will for the most part be sufficient to regard the carbon black-rubber bond as predominantly physical, with a relatively minor, but significant portion of the surface involved in the formation of chemisorptive attachments or polymer grafts. 

The impact strength of brittle thermoplastic materials is generally improved by adding small amounts of rubber, either pure or modified by grafting with the monomer or monomers constituting the matrix to be reinforced (1, 2, 3, 4, 5). As a rule, modification is achieved by monomer polymerization in the presence of the reinforcing elastomer, which is usually a butadiene polymer or copolymer (6, 7). 

Polymer blends containing one plastic phase and one rubbery phase will be emphasized in the next eight chapters. Depending on which phase predominates, such combinations yield impact-resistant plastics or reinforced elastomers. The briefer development of rubber-rubber blends given here belies the importance of the subject, since some 75% by volume of all rubber used is in blends. Also treated briefly are the plastic-plastic grafts, the best known of which are the castable polyesters. 

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