Development of novel flame‐retardant thermosets based on benzoxazine–phenolic resins and a glycidyl phosphinate

Modified novolac resins with benzoxazine rings were prepared and copolymerized with a glycidyl phosphinate. Their curing behavior and the thermal properties of the curing resins were studied. Copolymerization was studied with model compounds considering the functionality of the benzoxazine‐based phenolic resins and the easy isomerization of the glycidyl phosphinate. Phenolic novolac resin acts as an initiator but p‐toluensulfonic acid had to be used to decrease the curing temperature and to prevent glycidyl phosphinate from isomerizing. The materials obtained exhibited high glass‐transition temperatures and retardation on thermal degradation rates. V‐0 materials were obtained when the materials were tested for ignition resistance with the UL‐94 test. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 279–289, 2004