Ultra High Molecular Weight Polyethylene (UHMW) UHMW, also known as UHMW-PE, is a semi-crystalline thermoplastic material, known for its extremely high molecular weight and temporarytility, with a ntinuous use temperature range of up to 180° F (82° C). It also retains its key physical properties at temperatures as low as minus-22° F (minus-30° C).