Polybenzoxazines-New high performance thermosetting resins: Synthesis and properties

Polybenzoxazine is a newly developed addition polymerized phenolic system, having a wide range of interesting features and the capability to overcome several shortcomings of conventional novolac and resole type phenolic resins. These materials exhibit (i) near-zero volumetric change upon curing, (ii) low water absorption, (iii) for some polybenzoxazines T_g much higher than cure temperature, (iv) high char yield, (v) no strong acid catalysts required for curing, and (vi) release of no toxic by-product during curing. The molecular structure of polybenzoxazines offers enormous design flexibility, which allows tailoring the properties of the cured materials for a wide range of applications. In this review article, different synthetic strategies for the preparation of benzoxazine monomers and blends, their polymerization reaction mechanisms, and the structure-property relationships of the cured materials have been discussed.