Studies on New Type of Phenolic Resin by Ring Opening Reaction of Benzoxazine (V) Curing reaction of phenol-novolac based benzoxazine with bisoxazoline and the properties of the cured resin

摘要

As a series of studies on a new type of phenolic resin by the ring opening reaction of benzoxazines, two kinds of phenol-novolac based benzoxazines having different molecular weights were prepared from the corresponding phenol-novolacs, formaline, and aniline. Curing reaction of above benzoxazines with bisoxazoline and the properties of cured resins were investigated. With triphenylphosphite as a catalyst, the ring opening reaction of benzoxazine occurred at 170 deg C at first to generate a phenolic hydoroxyl group., and then the reaction of which with oxazoline ring followed at 200 deg C. The difference in the curing reactivity by the molecular weight of benzoxazines was as follows: the lower the mol3ecular weight, the faster the curing reaction due to molecular mobility. The both cured resins showed better heat- and water-resistance and fracture toughness, compared with the conventional cured resins from phenol-novolacs and bisoxazoline. As for the properties of the cured resin from different molecular weights of benzoxazines, the resin having a lower molecular weight showed better fracture toughness, while he resin having a higher molecular weight showed better heat- and water-resistance, and electrical insulation.