共聚单体对聚硼氮硅烷组成结构及性能的影响

Effect of Copolymerization Monomer on the Structure and Properties of Polyborosilazane

在以三氯化硼(BCl3)、甲基二氯硅烷(Si Cl2Me H)和甲胺(CH3NH2)为初始原料合成的Si BNC陶瓷纤维前驱体聚合物聚硼氮硅烷的基础上,通过添加不同质量分数的共聚单体3-氨丙基封端的聚二甲基硅氧烷对其进行共聚改性。分别采用傅里叶变换红外光谱(FT-IR)、核磁共振光谱(NMR)、凝胶渗透色谱仪(GPC)、热失重分析(TGA)以及力学性能测试等表征了改性前后前驱体聚合物的结构、分子量及其分布、陶瓷化得率及力学性能的变化。研究结果表明,共聚改性后Si-O-Si结构成功引入到前驱体聚合物分子链中,改性前驱体聚合物的数均分子量有所提高,分子量分布变窄。随着共聚单体添加量的增加,900℃时陶瓷化产率逐渐降低,前驱体纤维平均断裂伸长率由0.85%提高到3.62%,其柔韧性得到明显改善,而拉伸强度变化不大,因此有望改善前驱体纤维在后续加工过程中的退绕问题。

Polyborosilazane as the polymer precursor for Si BNC ceramic fiber was synthesized using BCl_3,SiCl_2 Me H and CH_3NH_2 as raw materials,which was modified with（3-aminopropyl）-terminated polydimethylsiloxane by co-polymerization.The structure of the modified polyborosilazane was investigated by Fourier transform infrared spectroscopy（FT-IR）and nuclear magnetic resonance（NMR）.The molecular weight and molecular weight distribution was determined by gel permeation chromatography（GPC）.The thermal properties of precursor polymer and the average elongation at break of the precursor fiber were investigated by thermogravimetric analysis（TGA）and tensile strength.The results showed that the flexible molecular chains containing Si-O-Si were introduced into polyborosilazane along with higher molecular weight and narrower molecular weight distribution.With the increase of the amount of copolymer monomer,the ceramic yield at 900°C gradually decreased and the average elongation at break of the precursor fiber improved from 0.85% to 3.62%.Therefore,the flexibility of the precursor fiber was improved obviously while the tensile strength had a little change.It is believed that the unwinding behavior of precursor fiber could be improved to be suitable for preparation of continuous Si BNC ceramic fiber.