Crystallisation process on the stage of the gel-to-solid transformation in thermo-reversible polyethylene gels

Abstract

The crystalline phase in gels and solid (gel derived) samples of ultra-high molecular weight polyethylene was studied using the low-frequency Raman spectroscopy and the differential scanning calorimetry methods. The Raman data evidence the presence in gels of tiny crystallites whose thickness (3-5 nm) depends on the sort of solvent used. After removal of the solvent by drying or squeezing the original gels, there appear some extra ordered regions (6-12 nm in size) coexisting in solid material with the primary crystallites which remain unchanged. It is concluded that the gel-to-solid transformation is accompanied by a secondary crystallisation process which is weakly (if ever) dependent on the incipient crystalline entities in gels. (C) 2002 Elsevier Science Ltd. All rights reserved.