Thermal degradation,mechanical behavior and Co 60 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 ~400ºC 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 (430–580ºC), the elimination of benzene (450–680ºC) and the rupture of Si-CH₃ and Si-OH (620–850ºC), within which the first degradation step can be retarded by the steric effect of the phenylene-silica framework. In order to study Co⁶⁰ 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 × 10⁵ 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.