Gelation/crystallization mechanisms of UHMWPE solutions and structures of ultradrawn gel films

The gelation mechanisms of ultra-high-molecular-weight polyethylene (UHMWPE) chains differed significantly in decalin and paraffin, although these are typical solvents used to gel spin UHMWPE fibers with high strengths and moduli. In both solvents, gelation was attributed to liquid liquid phase separation driven by concentration fluctuations during the initial stage. The gelation speeds and temperatures differed significantly in the two solvents. In decalin, solvent flowed from the gels, syneresis occurred during crystallization and dry gel films were prepared. In contrast, in paraffin, many nucleating points appeared immediately, and no syneresis occurred even after quenching to room temperature. To prepare dry gel films, paraffin was blotted with filter paper, and paraffin residues were removed in hexane. However, the small-angle X-ray scattering spectra from both films were similar, indicating crystalline lamellae and ultradrawing.