Thermal Study on the Copolymers of Phthalonitrile and Phenylnitrile-Functional Benzoxazines

摘要

Ortho-, meta-, and para-phenylnitrile-functional benzoxazines are polymerized at different compositions with phthalonitrile-functional monomers providing copolybenzoxazines of high thermal stability adn easy processabiltiy. The most positive effect on these properties is obtained on copolymerizing phthalonitrile- and ortho-phenylnitrile-functional benzoxazines. Thermal decomposition of these polybenzoxazines is studied by thermogravimetry (TGA). It is demonstrated that only 30 mol % of phthalonitrile-functional benzoxazine added to the ortho-phenylnitrile-substituted monomer improves char yield significantly from 59 to 77 wt %, which is the vlaue of neat phthalonitrile-based polybenzoxazine. Glass transition temperature (T_g) also dramatically increases from 180deg C for neat ortho-phenylnitrile polymer to 294deg C for the copolymer with 30 mol % of phthalonitrile-functional monomer. Additionally, the high melt viscosity of phthalonitrile-functional benzoxazines is dramatically decreased upon blending with phenylnitrile-functional monomer.