Study of the Effect of Organic Cationic S a l t s o n t h e P o l y m e r i z a t i o n o fBenzoxazine Monomer and Properties of their Polybenzoxazines

摘要

Polybenzoxazines are a novel class of thermosetting phenolic resins with attractive properties, including near-zero volume shrinkage upon polymerization, low water absorption, excellent mechanical properties, high thermal stability, and no reaction byproduct release [1]. Polymerization of benzoxazine resins is usually carried out without added initiators or catalysts in the temperature range of 160 and 220°C. However, lowering the polymerization temperature is sometimes desired. For some applications, addition of typical catalyst for cationic polymerization, such as metal complexes, is not desired as its presence show adverse effect on the polymer properties. Various catalytic systems have been reported for the polymerization of benzoxazine monomers [2], cationic salts being a promising one. It has been demonstrated that ammonium and phosphonium salts have high catalytic properties; however, their catalytic effect on polymerization of benzoxazine has not been explored yet [3]. Furthermore, it has been shown that the addition of epoxy into polybenzoxazine improves the polymer's mechanical properties through the addition of cross-linking sites [4]. The benzoxazine monomer used in this study was bisphenol A-aniline type ( BA-a), which was chosen since it is a simple, bi-functional monomer that readily goes through thermally activated ringopening polymerization. In this study, we will examine the effects of organic cations such as ammonium and phosphonium salts with and without additional reactive moieties towards the phenolic group on the polymerization temperature of BA-a and the resulting change in thermal properties.