XING Xi, WANG Huifeng, MU Shiwei, HUANG Xianhua, HAN Keqing, TENG Cuiqing, YU Muhuo
(State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Material Science and Engineering,
Shanghai 201620, China)
Abstract: Polyborosilazane as the polymer precursor for SiBNC ceramic fiber was synthesized using BCl3, SiCl2MeH and CH3NH2 asraw 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 ceramicyield 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 SiBNC ceramic fiber.
Key words: polyborosilazane; polymer precursor derived ceramics route; co-polymerization; flexibility