Factors Affecting the Processing of Epoxy Film Adhesives II. Moisture Content

Abstract Dielectric and thermomechanical analysis, infrared spectroscopy, and mechanical testing were used to study the changes which occur in the cure behavior of a 178°C (350°F) epoxy film adhesive, Hysol EA-9649. The response of the system was compatible with the catalyst type employed. The overall effect of increasing moisture content was an increase in flow accompanied by lower Tg values in the cured film with no loss in ambient temperature tensile lap shear strength. These effects are interpreted in terms of the dicyandiamide portion of the adhesive catalyst system reacting with the absorbed moisture resulting in a cured adhesive of different structure but equivalent in bonded joint strength to those made with low moisture content adhesive.