Phenolic resin has excellent mechanical properties and high temperature resistance, and is widely used in aerospace, architecture and other fields as the matrix resin of high⁃performance carbon / carbon composites or carbon / phenolic ablation resistant materials. The traditional phenolic resin releases volatiles during curing process, and its cross⁃linking structure after curing is deficient. For example, the tightly stacked rigid aromatic rings cause its high brittleness, the easily oxidized phenolic hydroxyl groups and methylene groups reduce its heat resistance and carbon residue rate. The multi⁃level structure design and modification of traditional phenolic resin is the key to satisfy its application in the field of new composite molding process and high⁃performance thermal protection. For example, the introduction of additive functional groups like propargyl groups and allyl groups into the novolac resin can achieve additive curing by thermal polymerization process. Through hydroxyl etherification reaction, epoxidation reaction or the introduction of molybdenum, boron, silicone and other components into the resin matrix, the molecular structure of resin can be regulated through chemical bonding and physical entanglement, then the structural design modification of phenolic resin can be achieved. This type of new phenolic resin essentially avoids the escape of small molecules during the curing process, and is easier to prepare high⁃quality composites. In summary, this paper focuses on several typical structural modified novolac resins and their research progress in the field of ablation protection. © 2023 Cailiao Daobaoshe/ Materials Review. All rights reserved.
