A study on the volumetric expansion of benzoxazine-based phenolic resin

Benzoxazine-based phenolic resin has recently attracted a great deal of attention due to its versatile properties. This paper explores yet another interesting property shown by this class of phenolic resin: volumetric expansion upon polymerization. It is proposed that the volumetric expansion of the benzoxazine resin is mostly due to the consequence of molecular packing influenced by inter- and intramolecular hydrogen bonding. The role of hydrogen bonding on the volumetric expansion has been studied by systematically changing the primary amine used in the benzoxazine monomer synthesis. In comparison to the other known expanding monomer, spiroortho compounds, this resin has been shown to have a high potential for structural/engineering applications. The homopolymers of this resin have a high glass transition temperature (T-g).