固/液态聚碳硅烷共混制备碳化硅纤维的研究

以超支化液态聚碳硅烷(LPCS)与固态聚碳硅烷(纯PCS)的共混物作先驱体,熔融纺丝;所得原丝再在热空气气氛中氧化交联,在高温氮气气氛中热裂解,得到碳化硅纤维。研究表明,15%(质量分数)LPCS的加入,可使纯PCS先驱体的纺丝温度,从285℃降低到225℃;纺丝性能和纤维表面质量明显提高;还可以提高氧化交联的效率,降低交联温度,从而减少纤维部分融并、粘结的弊端;虽然纤维的室温力学强度有所降低,但抗氧化性能提高,1400℃氧化交联后,力学性能几乎不变;而纯PCS的力学性能却降为原来的50%。

Study on the silicon carbide fibers from the blend of solid and liquid polycarbosilanes

A highly branched liquid polycarbosilane(LPCS) was mixed with a solid polycarbosliane(PCS) to give a polymer blend.It was then melt-spun into precursor fibers,oxidation-curd in hot-air,and converted into silicon carbide fibers by pyrolysis under nitrogen.It was found that the addition of the LPCS resulted in a significant drop on the spinning temperature from 285℃(solid PCS) to 225℃(with 15% LPCS),while the spinning ability and fiber’s surface of the polymer blend was also markedly improved over the solid PCS.Furthermore,the LPCS enhanced the oxidation curing,reducing the curing temperature and hence the tendency for fiber partial melting and sticking.Although the strength of silicon carbide fibers decreased owing to the presence of the LPCS,the oxidation resistance was improved.The strength of fibers with LPCS maintained the same after treatment in air in 1400℃,and the solid PCS fibers reduced to half the original.