Structure and mechanical properties of the hybrid films of well dispersed SiO2 nanoparticle in polyimide (PI/SiO2) prepared by sol-gel process

The hybrid films of well dispersed SiO2 nanoparticle in polyimide (PI/SiO2) were prepared through the sol-gel processing. The pure PI was synthesized from 4, 4',-oxydianaline (ODA) and pyromellitic dianhydride (PMDA). The residual amino groups which were controlled by the reactant stoichiometric ratio reacted with the coupling agent isocyanatopropyltriethoxysilane (ICTOS) to provide an organic-inorganic bonding. A series amount of tetraethoxysilane (TEOS) was then added, thus producing chemically bonded composite films. The films with different silica contents (0 wt %, 5 wt %, 8 wt %, 10 wt %, 13 wt %, and 15 wt %) were characterized by a variety of techniques including FT-IR, SEM, TGA, and tensile analysis. The results indicated that the chemical interaction between the two phases resulted in the formation of well-dispersed nanoparticles (20-30 nm) in the PI matrix, and superior thermal stability of hybrid films. The tensile measurement showed that the mechanical properties were markedly improved with incorporating various amount of silica, and the maximum of tensile strength was 105.4 MPa with10 wt % of silica concentration.