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

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.