Dynamic mechanical and thermal characterization of high-performance polybenzoxazines

Two polybenzoxazines are cured in an autoclave from the polyfunctional benz oxazine monomers, 8,8'-bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine) and 6,6 '-bis(2,3-dihydro-3-phenyl-4H-1,3-benzoxazinyl) ketone. The density and ten sile properties of these polybenzoxazines are measured at room temperature. Dynamic mechanical tests are performed to determine the T-g, crosslink den sity, and the activation enthalpy of the glass-transition process for these two polybenzoxazines. The effect of postcure temperature on the T-g of the polymers is investigated and discussed in terms of crosslink density. Four ier transform infrared (FTIR) spectroscopy is also applied for the molecula r characterization of the curing systems. Thermal properties of these polyb enzoxazines are studied in terms of isothermal aging and decomposition temp erature via thermogravimetric analysis. These two polybenzoxazines show mec hanical and thermal properties similar to or better than bismaleimides and some polyimides. They also show very high char yield after being carbonized in a nitrogen atmosphere. (C) 1999 John Wiley & Sons, Inc.