Crystallization kinetics of crosslinkable polymer complexes of novolac resin and poly(ethylene oxide)

Results of a study on the isothermal crystallization and thermal behavior o f both uncured and hexamine-cured novolac/poly(ethylene oxide) (PEG) comple xes are reported. The crystallization behavior of PEG in complexes is stron gly influenced by factors such as composition, crystallization temperature, complexation, and crosslinking. The time dependence of the relative degree of crystallinity at high conversion deviated from the Avrami equation. The cured complexes exhibited an obvious two-stage crystallization (primary cr ystallization and crystal perfection), and this was more evident at higher crystallization temperature and high PEG-content. The addition of a noncrys tallizable component into PEG caused a depression of both the overall cryst allization rate and the melting temperature. In general, complexation and c uring resulted in an increase in the overall crystallization rate. Complexa tion and curing are beneficial to the nucleation of PEG. Additionally, curi ng led to changes of the nucleation mechanism. Experimental data on the ove rall kinetic rate constant K-n were analyzed by means of the nucleation and crystal growth theory. For uncured complexes, the surface free energy of f olding, sigma(e), increased with increasing novolac content, whereas for cu red complexes, sigma(e) displayed a maximum with the variation of compositi on. (C) 1999 John Wiley & Sons, Inc.