KINETIC-PARAMETERS OF THE THERMOPLASTIC THERMOSET EPOXY REACTION BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

The melt state reaction. or fusion process of bisphenol-A and the diglycidyl ether of bisphenol-A can produce both linear phenoxy backbone chains and crosslinked network structures. The linear chains can be thought of as thermoplastic polymer, while the crosslinked molecular matrix is a thermoset; therefore, this resin system can be termed a thermoplastic/thermoset epoxy. Fourier transform infrared spectroscopy has been employed to study the chemical kinetics of the urea catalyzed system. The reaction of bisphenol-A and the diepoxide follows first order kinetics with respect to epoxide concentration, through 95 percent consumption of the epoxide for reaction temperatures of 130-degrees-C and above while lower temperatures show deviation from first order behavior at 75 percent conversion. When the differential form of the kinetic equation is used for analysis, the system follows first order behavior through 60 percent conversion of the epoxide at which point the order increases to a value of 1.5. Rapid spectral collection techniques have been employed to study this behavior for the temperatures 110 to 160-degrees-C. Upon incorporation of 3,4' bisphenol-A into the system first order behavior still adequately describes the kinetic behavior; however the rate of epoxide consumption and the activation energy are affected. Since the stoichiometric ratio of bisphenol-A to diepoxide was found to affect the rate constant, the reaction mechanisms of linear chain growth and crosslinking cannot be clearly distinguished by the sole use of this technique.