GLASS-TRANSITION TEMPERATURE (T(G)) VERSUS FRACTIONAL CONVERSION FOR A LINEAR THERMOSETTING POLYAMIC ACID ESTER POLYIMIDE SYSTEM

The relationship of the glass transition temperature, T(g), to fractio nal conversion, x, for the conversion of the cyclohexylmethyl ester of the benzophenone tetracarboxylic dianhydride-oxydianiline polyamic ac id to polyimide has been investigated using dynamic mechanical analysi s (torsion pendulum, TBA). The glass transition temperature and conver sion measurements were obtained on a single solvent-free polyamic acid ester specimen during cooling after heating to successively higher cu re temperatures. Conversion was determined from the intensity of a sub -T(g) mechanical relaxation peak that has been assigned to a relaxatio n of the cyclohexyl group. The resulting T(g) versus x relationship is nonlinear. The T(g) versus x relationship is adequately modeled using an expression derived by Couchman. (C) 1994 John Wiley & Sons, Inc.