Abstract
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 the above benzoxazines with bisoxazoline and the properties of the cured resins were investigated. With triphenylphosphite as a catalyst, the ring opening reaction of benzoxazine occurred at 170°C at first to generate a phenolic hydoroxyl group, and then the reaction of which with oxazoline ring followed at 200°C. The difference in the curing reactivity by the molecular weight of benzoxazines was as follows : the lower the molecular 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 the resin having a higher molecular weight showed better heat-and water-resistance, and electrical insulation.
