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 Tg 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.