Pyrolysis of hyperbranched polyborate modified phenolic resin

Hyperbranched polyborate (HBPB) is a new polymer with highly branched structures, plenty of functional end groups and excellent thermal resistance, which can be used as a positive modifier for phenolic resin (PR) to greatly increase the carbon yield of PR. In the present article, thermal properties and structural changes of HBPB modified PR (PR‐HBPB) during the pyrolysis are studied. The pyrolysis mechanism of PR‐HBPB is proposed to explain the increase of the carbon yield of PR‐HBPB. It is found that the carbon yields of PR‐HBPBs containing 10 and 20 wt% of HBPB are 71.3 and 73.1% at 800°C in nitrogen, which are higher than those of PR and HBPB but not the sum of the carbon yields of PR and HBPB in consideration of their mixing ratio. The increase of carbon yield of PR‐HBPB can be attributed to the combined effects of the excellent thermal stability of HBPB, the formation of BC 3 and B 2 O 3 , promoted graphitization by HBPB and the protection of B 2 O 3 on the edges of the graphite microcrystallites. POLYM. ENG. SCI., 2010.