Characterization and properties of hybrid composites prepared from poly(vinylidene fluoride-tetrafluoroethylene) and SiO2

Organic-inorganic hybrids were prepared using poly(vinylidene fluoride-tetr afluoroethylene) (P(VDF-TFE)) and tetraethoxysilane (TEOS) via a sol-gel pr ocess, and their crystallization and mechanical properties including the mo rphological features, were investigated. The hybrid films were transparent at TEOS contents up to 20 wt%. However, 3 0 wt% TEOS hybrid was less transparent due to formation of microvoids rathe r than pure polymer film. Crystallinity of P(VDF-TFE) in the hybrids increa sed with increasing TEOS content. This indicated that SiO2 played the role of nucleating agent in the polymer crystallization. The crystal structure o f P(VDF-TFE) in the hybrids was found to be B-phase according to X-ray diff raction measurements. No aggregation of SiO2 networks in the hybrids was ob served in small angle X-ray scattering measurements. The hybrid films, as well as pure P(VDF-TFE) film, showed clear yielding ph enomena in stress-strain relation. The yield strength, yield strain, and te nsile modulus of the hybrids increased with increasing TEOS content up to 2 0 wt%, but decreased abruptly at 30 wt% TEOS. It is interesting that the br eaking elongation of the samples was the highest at 10 wt% TEOS, two times higher than that of pure P(VDF-TFE) film. Consequently, the transparent hyb rid films could be obtained without any loss in either crystallinity of P(V DF-TFE) or mechanical properties. (C) 2000 Elsevier Science Ltd. All rights reserved.