聚硅氧烷 HPSO-VPSO 体系的交联和裂解

摘要

Joining of ceramics and ceramic matrix composites is of importance to extend the engineering applications of the materials. In view of the fact that successful joining of SiC ceramic has been achieved using the joining agent based on the mixture of hydrogen-containing polysiloxane and vinyl-containing polysiloxane (denoted by HPSO-VPSO), it is necessary to investigate the crosslinking and pyrolysis of the mixture in order to reach a better understanding of the mechanism of the joining. The crosslinking and pyrolysis of HPSO-VPSO were studied by thermogravimetry (TG), differential scanning calorimetry (DSC), infra-red spectroscopy (IR), and X-ray diffraction (XRD). The results show that, chloroplatinic acid (H2PtCl6) catalyst can effectively improve the crosslinking of HPSO-VPSO, which contributes to the increase of the ceramic yield. The mass loss of the crosslinked HPSO-VPSO is about 45% in the temperature range of room temperature to 1 200 ℃. The main mass loss takes place in the range of 370~825 ℃. The pyrolyzate of HPSO-VPSO pyrolyzed at 1 300 ℃ and below this temperature forms amorphous material. The crystallization of the pyrolyzate takes place between 1 300 ℃ and 1 400 ℃, leading to the formation of crystalline SiC and SiO2.%　　陶瓷及陶瓷基复合材料的连接技术具有重要的工程意义。鉴于采用以含氢聚硅氧烷(HPSO)和含乙烯基聚硅氧烷(VPSO)的混合物(用 HPSO-VPSO 表示)为主要成分的连接剂能够有效地连接 SiC 陶瓷，采用热重法(TG)、差热扫描量热法(DSC)、红外光谱(IR)以及 X 射线衍射(XRD)研究 HPSO-VPSO 体系的交联和裂解过程。试验结果表明，氯铂酸催化剂能促进 HPSO-VPSO 体系的交联，从而提高体系的陶瓷产率。HPSO-VPSO 从室温到1200℃的质量耗损约为45%，主要的质量耗损过程发生在370~825℃之间。在1300℃及以下裂解产物为非晶态物质，在1300~1400℃范围内裂解产物发生结晶，形成 SiC 和 SiO2晶体。