Pyrolysis mechanism of phenylboronic acid modified phenolic resin

Abstract

Phenylboronic acid (PBA) modified phenolic resin (PBPR) is one of the most important phenolic resins (PR) due to its good processability and high char yield. However, the pyrolysis mechanisms of PR and PBPR still remain poorly understood, which imposes limits on the synthesis, development and application of these materials. In this work, the pyrolysis process of PBPR has been studied through novolac resin (NR) and PBA crosslinked NR (PBNR) at high temperatures, and the reasons for the high char yield of PBPR were explored, as well. According to the results, the pyrolysis of NR begins with the cleavage reaction of the covalent single bonds in the molecular backbone. The release of volatile organic compounds (VOCs) such as monophenols and bisphenols formed by the cleavage of C—C single bonds is the major cause of the decreased char yield of NR at elevated temperatures. Meanwhile, increasing NR molecular weight and crosslinking NR could reduce the formation probability of VOCs, which is beneficial to obtaining the high char yield resin. In PBPR, the boronic ester linkages make the formation of VOCs more difficult and contribute to the high char yield of resin. The present work provides guiding significance for deeply understanding the pyrolysis mechanism of PR and PBPR to ensure their high thermal stability and char yield at high temperatures.