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-di carboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2'-bis(trifl uoromethyl)-4,4'-diamino biphenyl (PFMB), in refluxing m-cresol at hig h temperature. The polyimide film possesses two relaxation processes ( alpha and beta) above room temperature. The alpha-relaxation process i s attributed to the glass transition, and the beta-relaxation is the r esult of a sub-glass transition involving rotational motion in the PFM B diamine. An Arrenhius relation was utilized to investigate the beta- relaxation and an activation energy E(a) of 130 kJ mol(-1) was determi ned. This value of the activation energy is close to the value calcula ted based on the relationship derived from absolute reaction-rate theo ry assuming a zero-entropy contribution to the relaxation process prop osed 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.