Study On Heat-Resistant Hybrid Methylsilicone Porous Materials

Porous methylsilicone resins have great potential applications as heat-resistant materials owing to their backbone of Si-O-Si and porous structure. However, these applications inhibited because of the brittleness and demand of high thermal stability. In this dissertation, epoxy groups and iron oxide nanoparticles were doped into methylsilicone to improve both the mechanical properties and therma l stability.In this study, the molecular structure of methylsilicone resin-was modified by copolymerization of methylsilicone with γ- glycidoxypropyl trimethoxysilane(KH560) to increase the crosslinking degree of silicone.The influences of epoxy groups on the gel time,structure and properties of the silicone were studied. The modified resin were characterized by means of scanning electron microscopy(SEM), thermal gravimetric analysis(TG), Fourier transform infrared spectroscopy(FTIR), compression testing and N2 adsorption analysis.The SEM results showed that with the increase of KH560, the particle size of methylsilicone resin was reduced.The N2 adsorption results showed that with the increase of KH560,the volume of mesopores was reduced but the macropores increased. The compression test results showed that when adding 5wt% of KH560, the modified silicone porous materials had a maximum compressive rapture strength of 4.104 MPa but thermal gravimetric analysis results showed that its weight loss only increased 2.2% than the unmodified resin.Then the Fe2O3 and Fe3O4 were synthesized by liquid-phase method and were doped into the modified resin, respectively. The doped resin were characterized by means of SEM,TG,FTIR, compression testing and X-ray photoelectron spectroscopy(XPS). The FTIR results showed that both the doped resin retained Si-CH3 groups after heat-treatment for 30 minutes at 400℃ while the undoped sample had been completely converted to inorganic structure at the same condition and when Fe3O4 were added in an amount 10wt%, the doped resin retained Si-CH3 groups after heat-treatment for 30 minutes at 350℃ while the undoped one was turned into Si-O.When Fe3O4 were added in an amount 10wt%, the epoxy-modified methylsilicone resin showed a high resistance to compression performance(compression strength of 2.325 MPa when fractured) at room temperature, and had a mass retention rate of 82.33% after heated from room temperature to 1000 ℃ measured by TGA. The activation energies of methylsilicone resin, Fe2O3 doped epoxy-modified-methylsilicone resin and Fe3O4 doped epoxy-modified-methylsilicone were calculated by the Flynn-Wall-Ozawa(FWO) method. The activation energies were 48.2k J/mol, 174.9k J/mol and 285.4k J/mol when the conversion was 90%.