High-temperature polymer-silica composites and aerogels, and tear strengths of poly(dimethylsiloxane) networks reinforced with in situ precipitated silica

High-temperature organic-inorganic composites were prepared from a hydroxy-functionalized polybenzoxazole (HPBO) and silica using the sol-gel process. Proper bonding between the two phases was achieved by a bonding agent. Morphology studies indicated uniformly dispersed silica throughout the polymer. Modulus and ultimate strength were increased with increase in the amount of silica. Ultimate elongation and toughness were found to be large at low silica contents and relatively smaller at higher silica contents compared to the pure HPBO polymer. Thermal properties of the HPBO-silica composites were significantly improved and the extent of water absorption was decreased as the amount of silica present was increased.; High-temperature polymers, some poly(arylene ether)s and a HPBO copolymer, were toughened using dispersed rubbery phases generated using the sol-gel process. These rubbery phases were generated using combinations of sol-gel precursors with varying number of alkyl groups. Scanning electron micrographs showed uniformly dispersed particles in the material. In poly(arylene ether)s, a significant increase in toughness and ultimate elongation were achieved for samples prepared from relatively higher amounts of sol-gel precursor with higher number of alkyl groups. In HPBO samples having low levels of the rubbery phase, both toughness and ultimate elongation were increased with increasing the amount of rubbery phase. The results indicated improved thermal properties and decreased water absorption of the composites.; High-temperature sulfopoly(benzobisthiazole)-silica aerogels were prepared using the sol-gel process followed by the supercritical drying process. Morphologies of the samples were investigated using small angle x-ray scattering, N ₂ absorption measurements and transmission electron microscopy. According to the compressional stress-strain results, the deformability of silica aerogel is significantly increased by the incorporation of organic polymer into the inorganic silica network structure.; Tear strengths of poly(dimethylsiloxane) networks reinforced with in-situ precipitated silica were investigated. Electron micrographs showed well-dispersed, unagglomerated silica particles. Thermal properties of the PDMS networks were improved by the incorporation of silica. For unfilled materials, a steady tearing was observed. The filled materials showed unstable tearing, especially, at higher tearing rates. A marked increase in the tear strength occurred with increasing the silica content up to 10 wt% with less improvement as the silica content is further increased.