Copolymers, crystallization kinetic Avrami exponent

Crystallization Kinetics. Typical isothermal crystallization curves, which were measured using cast films of both types of copolymers, are presented in Figures 9 and 10. At the early stage of crystallization, the effect of the noncrystalline PS block on the rate curves was only shifts of the degree of crystallinity [1 — A(t)] vs. time curve along the time axis. However, the extent of shift does not correspond to PS content in the block copolymers. The change in crystallization temperature also causes the crystallization curves to shift. At the initial stage of crystallization, these rate curves could be superimposed on the rate curve of the homo-PTHF (Mn = 6 X 104), and an Avrami exponent... 

The overall crystallization kinetics of copolymers and their blends have been studied by DSC in the temperature range 1(X)-132°C [69]. For all examined blend compositions a single crystallization exotherm was observed at each T, whereas crystallization of mechanical mixtures of the copolymers showed separated exotherms of each component, thus supporting that the crystallization of melt mixed blends occurred from a homogeneous melt. The overall crystallization rate of copolymers was found to be affected by the copolymer structure and lower than that of PP homopolymer (BP < EP < PP), while the crystallization rate of the blends was intermediate between those of pure components (Fig. 10.12). The kinetics were analyzed by means of the Avrami equation (Eq. 10.14) the calculated values of the Avrami exponent for the blends, with average values of n from... 

---