Influence of poly (dihydroxybiphenyl borate) on the curing behaviour and thermal pyrolysis mechanism of phenolic resin

Abstract

In this study, phenolic resin (PR) that is modified with poly (dihydroxybiphenyl borate) (PDDB) is prepared. The chemical structure, thermal properties and structural evolution at high temperatures for cured PDDB/PR are investigated to understand the reason for high char yields. The results show that the phenylborates that are formed during curing are attributed to the high char yield of PDDB/PR (74%, 800 °C). Phenylborates can block parts of phenolic hydroxyl and effectively inhibit their thermal decomposition reaction. By tracking the resin residue and volatiles that are released during pyrolysis, it is determined that boron oxide and boron carbide are formed via pyrolysis and help reduce carbon loss. Introducing PDDB into PR improves the graphitization degree and graphite crystallites of carbonization products, which promotes the formation of ordered glassy carbon during pyrolysis. Additionally, the CF/PDDB/PR composites show excellent mechanical and ablation properties due to good interfacial adhesion between resin matrix and fibre. This method makes it possible for using PDDB to enhance the thermal properties of the polymer with lower cost, more functions and broader applications.