Ultrasonic characterization of a polymerizing epoxy resin with imbalanced stoichiometry

The effect of the mixing ratio of curing agent to epoxy prepolymer on the isothermal polymerization of common epoxy systems has been characterized by ultrasonic spectroscopy. During polymerization, changes in longitudinal ultrasonic wave properties (velocity and attenuation) were observed. These changes were related to the glass transition temperature of the resins. The profile of velocity and attenuation clearly depended on the mixing ratio. In all resins, the wave attenuation exhibited a peak in the primary relaxation (α).