Crystallization kinetics of poly (ε-caprolactone) in miscible thermosetting polymer blends of epoxy resin and poly (ε-caprolactone)

The results of a study on the isothermal crystallization kinetics and melting behavior of poly(epsilon -caprolactone) (PCL) in miscible thermosetting polymer blends of epoxy resin (ER) and PCL are reported. Blends of PCL and bisphenol-A-type ER were cured with 4,4 ' -methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) and compared with blends of PCL with uncured bisphenol-A-type ER, i.e. diglycidylether of bisphenol-A (DGEBA). The crystallization behavior of PCL in blends is strongly influenced by factors such as composition, crystallization temperature and curing. The time dependence of the relative degree of crystallinity at high conversion deviates from the Avrami equation. The addition of a non-crystallizable component into PCL causes a depression of both the overall crystallization rate and the melting temperature. The influence of curing on the crystallization and melting behavior of PCL is rather complicated. In general, curing leads to an increase of the overall crystallization rate of the blends and enhances the nucleation rate of PCL. Experimental data on the overall kinetic rate constant K-n are analyzed according to the nucleation and growth theory. For the uncured blends, the surface free energy of folding, sigma (e), increases with increasing DGEBA content, whereas for the cured blends, sigma (e) remains almost unchanged with the variation of composition. (C) 2001 Elsevier Science Ltd. All rights reserved.