Characterization of the interface in polymer-silica composites containing an acrylic silane coupling agent

Microscopic dynamics of the interfacial layer and macroscopic mechanical pr operties of [3-(acryloxy)propyl]trimethoxysilane (APMS) at a polymer-silica interface were studied using NMR and three-point bending tests. Wide-line deuterium NMR studies of deuterium-enriched [3-(acryloxy)propyl]trimethoxys ilane-d (APMS-d), showed that when chemically bonded to silica, the acrylic group of APMS moved rapidly at the interface with air, more slowly when co ated with a poly(methyl methacrylate)(PMMA) overlayer, and slowest when cop olymerized with methyl methacrylate. A two-component line shape was found f or the coated composite and these were assigned to relative immobile and mo bile surface groups. From three-point bend tests, the PMMA/glass-fiber comp osite, made from glass laminates treated with APMS, had almost two times th e flexural strength of a composite made from glass laminates not treated wi th APMS. Electron micrographs of the fracture surfaces revealed that the un treated fibers were smooth, while those from the APMS-treated glass were ro ugher, indicating the presence of polymer at the interface.