Kinetics of crystallization of polyamide 6 from the glassy state

Abstract

AbstractGlassy polyamide 6 was obtained by quenching the melt in liquid toluene at 210°K. On the DSC thermogram of such a polyamide a small endothermic peak of glass transition at 310°K, and an exothermic peak at 325°K of cold crystallization are observed (both temperatures were calculated by extrapolation to zero heating rate).The kinetics of cold crystallization was investigated in the range 321‐339°K by DSC technique using three different methods of measurement: 1) standard isothermal, 2) isothermal by Miller, and 3) nonisothermal by Ozawa. The data obtained from 1 and 2 were analyzed by the simple Avrami equation, and from 3 by a modified equation. It was confirmed that the exponent n is not constant; in the range up to 328°K it has an average value of 2.2, and then varies with the rise in crystallization temperature. Unfortunately, the mechanism of the variation of n is not known and this prevents the calculation of the crystallization rate from the nonisothermal dynamic data.Thus, an assumption was made that crystallization follows first‐order kinetics: K and t0.5 for different temperatures were calculated; the Arrhenius function was plotted; and from it the activation energy of 69.7 kcal/mole was estimated.