Low exotherm, low temperature curing, epoxy impregnants

Abstract

Epoxy-type impregnating compounds, which are useful for electrical potting or encapsulation, plastic tooling, and fiber-reinforced composites, comprise a resin component and a stoichiometric amount of a curative and have a curing temperature of less than about 120.degree. F. (49.degree. C.). The resin component is the diglycidyl ether of bisphenol A, either alone or as a mixture with up to about 15 wt % of at least one reactive monoepoxide diluent or up to about 50 wt % of at least one reactive diepoxide diluent, the diluent having a viscosity of less than about 200 cp. The curative is a mixture of cycloaliphatic diamines, comprising from about 20 to 80 wt % of at least one sterically-hindered cycloaliphatic diamine and the balance at least one sterically-unhindered cycloaliphatic diamine. These epoxy compounds are unique because they can be handled in relatively large bulk without concern for dangerous runaway exotherms. In addition, they result in useful products with a moderate service temperature range, without the necessity of high temperature cures. The advantages of the low temperature cure are lower residual stress in the cured product, better dimensional control in molding, and lower energy expenditure.

Dependencies are inferred from the claim text.