Effect of resin formulation and reaction temperature on the curing kinetics of vinyl ester resins

The curing reaction in the mixture of vinyl ester and styrene monomers is a free radical chain growth polymerization. Possible reactions include homopolymerization of the vinyl ester and styrene monomers as well as copolymerization of these components. The rates of the competing reactions give insight into the network morphology, and thus the resulting material properties. With the use of Fourier Transform Infrared (FTIR) spectroscopy, molecular information can be gathered to elucidate reaction pathways under different processing conditions. In this work, the cure of vinyl ester resins mixed with various amounts of styrene was analyzed at multiple isothermal temperatures using FTIR spectroscopy. Styrene monomer was found to react at a slower rate, yet it reached a greater extent of conversion than the vinyl ester monomer. The relative rate of reaction of vinyl ester components may provide a better understanding of resulting network structure in terms of extent of microgel formation and intermicrogel reaction. In addition to FTIR spectroscopy, sol-gel analysis and Atomic Force Microscopy (AFM) techniques are being used to determine the relation among the cure and network morphology. This work forms the basis for evaluating cure behavior in the interphase region along a fiber surface.