Brillouin scattering study of epoxy adhesive layers during cure

The isothermal curing process of thin epoxy adhesive layers (mixture of a b isphenol A-based epoxy prepolymer and an aliphatic diamine curing agent) ha s been investigated. The Brillouin scattering technique with 90 degrees A s cattering geometry enables simultaneous measurements of longitudinal and sh ear wave properties in the GHz range. Observed longitudinal and shear wave velocities showed similar changes during cure. They rapidly increased and g radually became constant, reflecting the elastic changes of the epoxy layer . The final velocities, however, clearly depended on the curing temperature . Taking the glass transition process of epoxy resins into consideration, t hese curing behaviors in thin layers are discussed. (C) 2000 Elsevier Scien ce B.V. All rights reserved.