Thermal degradation, mechanical behavior and Co60 gamma-irradiation induced effects of poly(methylphenylsiloxane)/phenylene-silica hybrid material

Poly(methylphenylsiloxane) (PMPS)/phenylene-silica hybrid material was prepared by a two-step sol-gel process. In the structure of the hybrid system, the phenylene-silica framework was imported into the crosslinked PMPS matrix to obtain interpenetrating networks. The results of thermogravimetric analysis (TGA) and mechanical tests show that the products exhibit excellent thermal stability at similar to 400 degrees C in an inert atmosphere and a tensile strength up to 25.9 +/- 1.7 MPa. The investigation of thermal degradation mechanism by TGA coupled with Fourier transform infrared (FTIR) spectroscopy (TGA-FTIR) reflects the linear segments unzipping (430-580 degrees C), the elimination of benzene (450-680 degrees C) and the rupture of Si-CH3 and Si-OH (620-850 degrees C), within which the first degradation step can be retarded by the steric effect of the phenylene-silica framework. In order to study Co-60 gamma-irradiation induced effects, the hybrid products after irradiation were also studied by the same characterization, showing slightly increased crosslinking degree of PMPS and unchangeable initial degradation temperature at an irradiation dose of 1.6 x 10(5) Gy. The mechanical behavior for hybrid products, including tensile strength and coating film properties, was well maintained under the effect of irradiation. An increase of phenylene groups inserted in the phenylene-silica framework was confirmed to induce more significant steric interactions to polymer backbones. This effect permits the hybrid products to enhance thermal and irradiation resistance, as well as mechanical strength.