A KINETIC-STUDY OF THE REACTION OF EPOXIDIZED RUBBER AND CARBOXYLIC-ACIDS

The coatings industry has long been interested in nontoxic multifunctional crosslinking agents that do not emit volatile organic compounds (VOCs) during curing. Ring opening of epoxides is an ideal chemical reaction for there are no accompanying VOCs. Therefore, we have investigated the feasibility of a novel epoxide reagent as a multifunctional crosslinking agent. Specifically, epoxidized poly-cis-isoprene has been synthesized and evaluated as a reactant with a variety of carboxylic acids via isothermal differential scanning calorimetry. Accordingly, we have measured the reaction enthalpy at various temperatures and reactant concentrations. The change in heat flow with time is proportional to the change in the reactant concentration with time since ring opening of epoxides with carboxylic acids gives chain modification via ester formation. We have also determined the reaction order and energy of activation. Three acids ranging in pKa from 1.26 to 4.95 were studied and provided activation energies ranging from 42.9 to 115.9 kJ/mol. The reaction order was determined to be first order in acid.