Surface modification of silica with ultrahighmolecular weight polyethylene (UHMWPE)

UHMWPE (Ultrahighmolecular Weight Polyethylene) was attached to silica using a two step process, in which the first step involves silanating the silica surface with a 0.5-1.2 mole % vinyltrimcthoxysilane-ethylene copolymer (PE-silane), and in which the UHMATE (M-w = 3-6 x 10) is solution coated onto the silanated silica in the second step. Glass beads (3.6 mum diameter) were cleaned using distilled water or refluxed with 5% aqueous Na2S2O8, to remove metallic surface contaminants, were used for UHMWPE attachments. SEM and optical microscopy showed individual particles. TGA (thermogravimetric analysis) studies confirmed the attachments as well as their stability after attachment. The integrity of the coatings was examined by SEM following treatment with HF, which left thin "skins" of polymer remaining. Both washing methodologies for the glass beads provided similar UHMWPE coatings. Bend bars (10) prepared using UHMWPE coated beads show no adverse drop in moduli and strength.