Effect of Rubbery Phase Dispersed in Glassy Matrix on Impact Strength

2 Effect of Rubbery Phase Dispersed in Glassy Matrix on Impact Strength 

The necessary properties of the rubbery phase have been discussed by many authors [37,39-42]. They are as follows  

It is necessary for the dispersed rubbery substance to have a Tg value lower than the temperature at which the high-impact material is to be used. Many elastomers will satisfy this condition they are butyl rubber, polybutadiene, SBR, BAN, ethylene-propene elastomer, polychloroprene, EVA, polyisoprene, polyacrylates, PIB, and chlorinated polyethylene (CPE) elastomers. However, they are not all useful for specific blends such as PVC-based blends because they do not fulfill the other necessary properties. 

However, the rubbery phase should be immiscible with the matrix polymer. Rubbers miscible with glassy polymers function as macromolecular plasticizers for these polymers, showing a decrease in Tg value, toughness, elasticity modulus, and so on. When miscible rubbers are used in small quantity, they produce antiplasticization (see Section 1.5). Polyurethane elastomers are typical examples of those miscible rubbers [40]. 

The optimum morphology is another property necessary for good impact strengths of two-phase polymer systems. According to a theory that attributes improved impact resistance to the presence of rubbery particles, it is necessary to obtain a solid dispersion made of rubber particles of 1000-2000 nm in diameter within the glassy polymer matrix, as shown in Fig. 3.4 [44]. On the other hand, another theory assumes that the rubbery modifier functions as a continuous lattice-like phase having a honeycomb structure [45-47]. If the 

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