High char yield novolac modified by Si-B-N-C precursor: Thermal stability and structural evolution

In this contribution, novolac modified by CSEB ceramic precursor (B,B,B-tris[(chlorodimethylsily1)ethane]borazine, CSEB) was synthesized successfully. The corresponding molecular structure, chemical state and thermal property were characterized by Fr-IR, Raman spectra, XPS, NMR and TGA. Meanwhile, DTA/TG/MS test was also performed to track the weight loss and gas evolution of modified novolac during the thermal degradation. CSEB could obviously improve the thermal decomposition temperature and the char yield of novolac. The maximum decomposition rate temperature is increased up to 575.2 degrees C. The char yield is increased to 75.5% at 800 degrees C, 72.6% at 1000 degrees C and 68.7% at 1200 degrees C, respectively. The improvement of the thermal stability of modified novolac could be mainly attributed to the incorporation of six-membered borazine ring (B3N3), elements of Si, B and N. The B3N3 ring remains stable at 1400 degrees C. And fixed structure Si-O-x was formed during heat treatment. Moreover, CSEB also promote the graphitization. (C) 2017 Elsevier Ltd. All rights reserved.