New type of phenolic resin—The curing reaction of bisphenol A based benzoxazine with bisoxazoline and the properties of the cured resin. III. The cure reactivity of benzoxazine with a latent curing agent

Abstract

Abstract The curing reaction of a bisphenol A based benzoxazine [2,2‐bis(3,4‐dihydro‐3‐phenyl‐1,3‐benzoxazine) propane (Ba)] and bisoxazoline with a latent curing agent and the properties of the cured resins were investigated. With a latent curing agent, the ring‐opening reaction of the benzoxazine ring occurred more rapidly, and then the phenolic hydroxyl group generated by the ring‐opening reaction of the benzoxazine ring also reacted with the oxazoline ring more rapidly. The cure time of molten resins from Ba and bisoxazoline with a latent curing agent was reduced, and the cure temperature was lowered, in comparison with those of resins from Ba and bisoxazoline without a latent curing agent. The melt viscosity of molten resins from Ba and bisoxazoline with a latent curing agent was kept around 50 Pa s at 80°C even after 30 min, and molten resins from Ba and bisoxazoline with a latent curing agent showed good thermal stability below 80°C. However, above 170°C, the curing reaction of Ba with bisoxazoline with a latent curing agent proceeded rapidly. Cured resins from Ba and bisoxazoline with a latent curing agent showed good heat resistance, flame resistance, mechanical properties, and electrical insulation in comparison with cured resins from Ba and bisoxazoline without a latent curing agent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008