Modified Epoxy Adhesives and Primers

摘要

A range of monoepoxy additives for epoxy resins, and non-reactive additives forpolyimides, have been examined with a view to understanding the mechanism of their 'fortifying action, and to examine their usefulness in adhesive applications. An increase in strength of 50% and an increase in modulus of 40% is achievable by this method, along with a decrease in water uptake, decreased expansion coefficient, and a modified failure mechanism. These properties of the bulk resin translate into modest improvements in adhesive bond performance, particularly for low temperature cured systems, and in humid environments. It should be cautioned, however, that the effect of the additives will vary with the geometry of the joint and the test procedure. The mechanism of property modification is explained on a quantitative basis using the concept of free volume. The contributions of molecular interactions and of the depression in glass transition temperature are separated. The monoepoxy additive are shown to function more efficiently than unreactive additives in epoxy systems. A synergism between these additives and CTBM rubber modifiers is also reported.