The Influence of Copolymerization on Thermal Properties

FIGURE 6.5 Specific volume-temperature relation for crystallizable polymers. Numbers apply to Example 6.8. 

Polymer blends, which are mixtures of two or more different homopolymers, are also commonly used in commercial materials. Except in the rare case where interpolymer crystallites can form, blends exhibit multiple TgS and Tm s, one for each component of the blend. 

FIGURE 6.6 Phase diagram for a random copolymer system. 

A copolymer in region 5 is atypical amorphous, glassy polymer hard, rigid, and usually brittle. Again, if the polymer is pure, it will be perfectly transparent. PMMA (Lucite, Plexiglas) and PS are familiar examples of homopolymers with these properties. 

Copolymers in regions 4 and 6 consist of crystallites in an amorphous, glassy matrix. Since both phases are rigid, the materials are hard, stiff, and rigid. Again, the two phases impart opacity. Nylon 6/6 and nylon 6 are examples of homopolymers in a region below both Tg and Tm at room temperature. 

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