聚硼硅氮烷的合成及其流变性能研究

以二氯甲基硅烷、三氯化硼、六甲基二硅氮烷为起始原料，采用缩聚法合成了一种新型SiBNC陶瓷先驱体-聚硼硅氮烷(PBSZ)。通过调节原料二氯甲基硅烷的用量可获得不同软化点的先驱体。通过改进的毛细管流变仪，首次对熔融纺丝状态时聚硼硅氮烷(PBSZ)的流变特性展开了研究。结果表明：PBSZ熔融纺丝时，剪切速率在10～110s-1时，为切力变稀流体。非牛顿指数为0.83～0.90，粘流活化能约为142KJ/mol，表观粘度440～2460Pa·s，PBSZ对温度变化的敏感性较聚碳硅烷小，可纺温区较宽。PBSZ纺丝性能良好，纤维连续无断头长度﹥1600m，纤维直径﹤20μm。

Synthesis and Rheological Property of Polyborosilazane

Polyborosilazane (PBSZ), a novel precursor to SiBNC ceramic, was synthesized via cocondensadition approach by using dichloromethylsilane (MeHSiCl2), boron trichloride (BCl3) and hexamethydisilazane ((CH3)3SiNHSi(CH3)3) as the starting materials. Precursors with different softening point can be obtained by altering the dosage of MeHSiCl2. Rheological property study show that PBSZ melt is a typical shear stress diluting fluid and the shear rate, the flow index, the viscous flow activation energy, the apparent viscosity is 10~110 s-1, 0.83~0.90, 142 kJ/mol, 400~2400 Pa·S, respectively. The as-synthesized polyborosilazane shows good processability in wide temperature range and endless polymer fibers can be obtained in 87℃ in N2 atmosphere.