 Benzoxazines are bicyclic heterocyclic compounds containing one oxygen and one nitrogen atom in a doubly unsaturated six-member ring, specifically a 1,3-oxazine ring, fused with a benzene ring.The systematic benzoxazines IUPAC name of the unsubstituted monomer is 3,4-dihydro-3-phenyl-2H-1,3-benzoxazines.Benzoxazines are products of condensation between an amine, a phenol and formaldehyde, used to produce thermoset resins or thermosetting polymer.