Gel-to-solid transition in polyethylene from the viewpoint of the crystallization process

Abstract

The crystalline phase in gels and solid gel-derived samples of ultrahigh molecular weight polyethylene was studied using the infrared spectroscopy, low-frequency Raman spectroscopy and wide-angle X-ray scattering methods. The spectroscopic data evidence the presence in gels of tiny crystallites whose thickness (3-5 nm) depends on the sort of the solvent used and it is insensitive neither to the concentration of the diluted solution, nor to the molecular weight of the polymer. After removal of the solvent, there appear crystalline clusters composed of closely attached folded platelets. The total thickness of these stacked entities is about 10-20 nm while their transverse size reaches similar to50 nm. In addition, the crystalline domains in the gelled material exhibit a kind of mosaic structure which is much more pronounced in solid xerogels than in wet gels.