Polymer blends of poly(ε-caprolactone) and poly(vinyl methyl ether) -: thermal properties and morphology

We report on thermal properties and the phase behaviour of polymer blends comprising poly(epsilon-caprolactone) (PCL) and poly(vinyl methyl ether) (PVME). The blends were subjected to different thermal histories. In all cases, the fraction of PCL, that crystallizes in the blends, increases slightly up to 30% content of PVME. Crystallization rates of PCL are found markedly reduced in blends as compared to neat PCL. Ring-banded spherulites develop during isothermal crystallization. Radial growth rates of spherulites decrease exponentially with increasing PVME content up to approximately 40% of PVME. At higher PVME contents non-exponential decrease was observed. Melting points of PCL in blends were determined applying a step-wise annealing procedure. The glass transition temperatures of the blends reveal formation of PVME-rich phases even after rapid quenching of the homogeneous melt owing to crystallization of PCL. Lower critical solution temperature behaviour of the melts could be determined tentatively by optical inspection. The homogeneous melt phase-separates above approximately 190 degrees C. (C) 1999 Elsevier Science Ltd. All rights reserved.