The Preparation Of Nano Fe₂O₃ Modified Polymethylsiloxand Resin And Properties Of It's Composites

The silicone resin matrix composites will be the first choice for the wave transmission materials in intercontinental missile warhead and space shuttle, due to theirs low heat expansion coefficient and light weight, especially the properties of high temperature stability and dielectric. In present paper, the methysilicone resin and its composites which were modified with nano Fe₂O₃ were prepared. And the heat-resistance property, mechanical performance and electric characteristic in high temperature of the composite were also studied.The methylsilicone resin of low carbon content was prepared by methyltriethyoxysilane. The structure of the prepared methysilicone resin was characterized by FT-IR and solid ²⁹S NMR, and it is confirmed that the prepared methysilicone resin contained hydroxyl group. Furthermore, the heat–resistance performance and thermal oxidative degradation stability of the aforementioned methysilicone resin were also invested through thermogravimetric analysis. The result indicated that the prepared methysilicone resin had good thermal stability and thermal oxidative degradation stability at elevated temperature.In order to avoid the agglomeration of Fe₂O₃ nano-particle, the polybutylmthacrylate (PBMA) was used to modify Fe₂O₃ nano-particle, and the modified Fe₂O₃ nano-particle was characterized by IR, XPS and TG. The result revealed that the PBMA had grafted onto Fe₂O₃ nano-particle surface. Then, the resulting Fe₂O₃ nano-particle was mixed with methysilicone resin, and the compatibility and distribution between Fe₂O₃ nano-particle and methysilicone resin was evaluated by wettability test, TEM and TG. It is found that the modified Fe₂O₃ nano-particle had well distribution in methysilicone resin. Thus, the studies of effect of adding content of Fe₂O₃ nano-particle on heat-resistance performance of methysilicone resin were achieved. Through the analysis of TG, TG-IR, ²⁹Si-NMR and XPS, it can be conclude that with the addition of Fe₂O₃ nano-particle, the thermal stability was improved and the content of residual carbon was decreased.The kinetic parameters of methylsilicone resin and the resin modified by Fe₂O₃ nano-particle were determined using Flynn-Wall-Ozawa and Friedman methods. Coats-Redfern and Master curve methods were used to study the solid-state decomposition mechanism of the"unzipped"and"rearranged"degradation. The results showed that the activation energy of methysilicone resin modified by Fe₂O₃ nano-particle was higher that that of methysilicone resin untreated. Furthermore, a two-reaction kinetic model was proposed, and the results obtained form this model had well agreement with experimental results.The effect of resin content of methysilicone resin, impurity, pores, temperature, interface and moisture absorption on the dielectric properties of polymethysilicone resin composite were studied. The results indicated that the dielectric properties of methysilicone resin in high temperature were improved with the addition of Fe₂O₃ nano-particle. Moreover, the mechanical properties of polymethysilicone resin composite were also carried out. It showed that the flexural strength and interlaminar shear strength of silica glass fiber/methylsilicone resin composites were all improved after the addition of Fe₂O₃ nano-particle.