聚硼硅氮烷的表征及其流变性能

Characterization and Rheological Property of Polyborosilazane

以二氯甲基硅烷、三氯化硼、六甲基二硅氮烷为起始原料,采用缩聚法合成了新型SiBNC陶瓷前驱体——聚硼硅氮烷(PBSZ),其产率达90%。通过调节二氯甲基硅烷的用量可获得不同软化点的前驱体。采用改进的毛细管流变仪,首次对熔融纺丝状态时PBSZ的流变特性进行了研究。结果表明,PBSZ熔融纺丝时,剪切速率在10～110s-1范围内时,为切力变稀流体,非牛顿指数为0.83～0.90,表观粘度为440～2460Pa.s,粘流活化能约为142kJ/mol。PBSZ纺丝性能良好,纤维连续无断头长度>1600m,纤维直径<20μm。

Polyborosilazane （PBSZ）, a novel precursor of SiBNC ceramic, was synthesized via polycondensation approach with a yield of about 90% （mass fraction） from dichloromethylsilane（ MeHSiC12 ） , boron trichlo-ride （ BCI3 ） and hexamethydisilazane （ （ CH3 ） 3 SiNHSi （ CH3 ） 3 ）- Precursors with different softening points can be obtained by altering the dosage of MeHSiCl2. Rheological study shows that PBSZ melt is a typical shear thinning fluid. The shear rate, the flow index, the apparent viscosity and the viscous flow activation energy are 10 - 110 s^-1, 0. 83 - 0. 90, 440 - 2 460 Pa ·s, and 142 kJ/mol, respectively. The as-synthesized polybo- rosilazane shows a good melt-spinning processability and continuous fibers with diameter 〈 20 μm and length 〉 1 600 m can easily be obtained.