Melting transition temperature free volume, effect

Crystallization may take place only within the temperature region limited on the upper side by the melting point, T, and on the lower side by the glass transition temperature, T. The crystallization behavior very much depends on the state of miscibility, as well as on the nature of other blend s components. In miscible blends Tg is a monotonic function of the components T s. When the second component is amorphous, its presence can either decrease or increase the tendency of the first resin to crystallize. The process depends on the blending effects on T and on the chain mobility (the free-volume effect). When T of the amorphous component is lower... 

A plasticiser is a material incorporated in a plastic to increase its workability and flexibility or distensibility. The melt viscosity, elastic modulus and Tg of a plastic are lowered by a plasticiser addition. There are several theories to explain plasticiser effects such as the lubricity, gel, and free volume. Plasticisers are essentially nonvolatile solvents and therefore, polymer and plasticiser compatibility is very important and the solubility parameter difference (A8) should be less than 1.8. When present in small amounts plasticisers generally act as antiplasticisers, (i.e., they increase the hardness and decrease the elongation of polymers). Figure 6.12 illustrates the effect of plasticiser on modulus. Increasing concentration of the plasticiser shifts the transition from the high modulus (glassy) plateau region to the low, i.e., to occur at lower temperature [9]. 

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