聚碳硅烷纤维的不熔化与SiC纤维制备研究

Research on Curing of Polycarbosilane Fiberand Preparation of SiC Fiber

以聚二甲基硅烷(PDMS)为原料,在高压釜内高温高压反应制备了聚碳硅烷(PCS)先驱体,经熔融纺丝制备了PCS纤维,研究了在190℃下不同不熔化时间对PCS纤维氧化增重、Si-H键反应程度、凝胶含量、氧含量及最终SiC纤维氧含量与性能的影响。研究表明,在不熔化过程中,PCS结构中的Si-H键与氧反应,在PCS分子间形成Si-O-Si交联结构。随着不熔化时间的延长,PCS纤维发生氧化增重、Si-H键反应程度提高、凝胶含量增加,SiC纤维中氧含量也逐渐增加。在不熔化保温3h,制备的SiC纤维强度可达2.52GPa。随着不熔化时间的进一步延长,SiC纤维氧含量增加,其强度逐渐降低。

The polycarbosilane (PCS), which was the precursor of SiC fiber was synthesized in an autoclave by thermal decomposition of polydimethylsilane (PDMS). PCS fiber was obtained by melt-spinning. The influence of curing time at 190°C on the weight gain, Si-H bond reaction degree, gel content and oxygen content of PCS fiber was investigated. The cured PCS fibers were then pyrolyzed up to 1250°C at a tube furnace in a N2 flow. The oxygen content and properties of SiC fibers were determined. The results show that Si-H bond in the molecular structure of PCS reacts with oxygen during the curing process. Si-O-Si linked structures are therefore produced among PCS moleculars. The weight gain, Si-H bond reaction degree, gel content and oxygen content of PCS fiber increase with increase of the curing time. The oxygen content of SiC fiber increases gradually also. When the PCS fiber is cured for 3 hours and pyrolyzed, the tensile strength of SiC fiber can reach 2.52 GPa, and decreases gradually when the curing time is more than 3 hours.