Based on B-trichloroborazine (TCB) with boron-nitrogen ring structure, the monomer was synthesized by substitution reaction with different ratio of methylamine/dimethylamine, then the corresponding polyborazine was obtained through thermal polymerization. The chemical component and structure of polyborazine were analyzed, and the influence of different methylamine/dimethylamine molar ratio on the polyborazine properties and spinnability were examined. The results indicated when the molar ratio of methylamine/dimethylamine was 1∶2, the polyborazine with chemistry stability was prepared through thermal polymerization at 180 ℃. The melting point, number average molecular weight and polydispersity index of polyborazine precursor was 83 ℃, 7603 and 1.80, respectively. The polyborazine precursor could possess nearly linear molecule skeleton and show good processability. The precursor fibers were prepared with average diameter 10～15 μm and BC_0.76N_1.39H_2.5 structure, which suggested that the as-achieved polymer could be used as a precursor for BN ceramic fibers.

Key words: B-trichloroborazine, polyborazine, boron nitride fibers precursor, preparation