THERMAL DYNAMIC RELAXATION AND ENTHALPY DISTRIBUTION OF AN AROMATIC POLYIMIDE FILM - 6FDA-PFMB

An aromatic polyimide, 6FDA-PFMB, was synthesized from 2,2'-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2'-bis(trifluoromethyl)-4,4'-diamino biphenyl (PFMB), in refluxing m-cresol at high temperature. The polyimide film possesses two relaxation processes (alpha and beta) above room temperature. The alpha-relaxation process is attributed to the glass transition, and the beta-relaxation is the result of a sub-glass transition involving rotational motion in the PFMB diamine. An Arrenhius relation was utilized to investigate the beta-relaxation and an activation energy E(a) of 130 kJ mol(-1) was determined. This value of the activation energy is close to the value calculated based on the relationship derived from absolute reaction-rate theory assuming a zero-entropy contribution to the relaxation process proposed by Starkweather. The distribution of relaxation times, or rather enthalpies, for the beta-relaxation is obtained. The alpha-relaxation, however, obeys a WLF-type equation.