Studies on crystallization kinetics of nylon 6-polyoxypropylene-nylon 6 copolymers

The crystllization kinetics of anionic-prepared nylon6-poly(oxypropylene) 1000-nylon 6 (NPN) block copolymers containing 1.20 to 8.76 wt% poly(oxypropylene)(POP) were studied. The thermograms of isothermal and nonisothermal differential scanning calorimetry of NPN block copolymers obtained were used for the study. The Avrami equation was used to analyze the isothermal crystallization of NPN nylon block copolymers. The Avrami exponent n obtained in the temperature range of 180 to 200 °C was 2.0 to 2.5. It was not similar to that for nylon 6 reported in literature. The activation energies of crystallization for the nylon block copolymers were smaller than that of nylon 6, and showed a minimum with POP content. The equilibrium melting point increased as the POP content decreased. For the nylon block copolymers with lower POP content, the slopes of T_c vs. T_m plots were higher than the values reported elsewhere. The Ozawa plot was used to analyze the data of nonisothermal crystallization. The obvious curvature in the plot indicated that the Ozawa model could not fit our system well, and there was an abrupt change of the slope in the Ozawa plot at a critical cooling rate.