THE EFFECT OF STOICHIOMETRY ON CHAIN SEGMENT AND ION MOBILITY IN PARTIALLY POLYMERIZED EPOXY SYSTEMS

The temperature dependence of steady-shear viscosity and ionic conduct ivity were measured for a series of unreacted mixtures and partially c ured, ungelled samples of diglycidyl ether of bisphenol-A (DGEBA) and an amine cross-linking agent, diamino diphenyl sulfone (DDS). Six stoi chiometric ratios of epoxide groups to amine hydrogens were examined. Free volume expressions were used to model the temperature dependence of the conductivity and viscosity for the unreacted DGEBA-DDS mixtures . In addition, these expressions were combined to successfully correla te changes in viscosity and conductivity during the DGEBA-DDS polymeri zation prior to gelation. It also was demonstrated that the change in weight average molecular weight during polymerization could be interpr eted from the dielectric data. Through studying variations in the stoi chiometry, it was possible to examine the effects of changes in chemic al structure and ion concentration on the fitted parameters in the fre e volume models. The inherent ion transport factor (zeta0) was found t o be inversely proportional to the concentration of ions in the test s amples. The fractional free volume for segmental motion (B) was found to increase with an increase in the glass transition temperature and t o be a function of the rigidity of the polymer (C) 1995 John Wiley & S ons, Inc.