Pyrolysis behavior of the nanoporous phenolic matrix and the resultant microstructure and property evolution in the composites

Phenolic pyrolysis greatly affects the thermal protection performance and structural strength of phenolic ablatives, but understanding the complex process remains a challenge. In this study, fast pyrolysis in a specially designed fixed reactor and an in situ TG-FTIR-MS experiment are proposed to elucidate the pyrolysis behavior of a nanoporous phenolic matrix (NPM). Furthermore, the resultant evolution of microstructures and properties in composites are illustrated. The fast pyrolysis experiments show that H2, CH4 and CO are the main components of the gas phase, while aromatic compounds are the main components of the condensed liquid phase. The analysis of in situ TG-FTIR-MS experiments reveals the slight weight loss of NPM at low temperature is mainly due to the escape of H2O and CO2, while the main weight loss of NPM at high temperature is caused by the escape of aromatic compounds. Moreover, the corresponding variations in the mechanical and thermal insulative performances of nanoporous phenolic composites (NPCs) are analyzed. This work would promote the development and application of porous phenolic composites in thermal protection system fields.