Influence of DICY crystals on electrical and mechanical behaviour of the epoxy/glass composite

Epoxy/glass composites are widely used in the manufacture of quite a number of electrical machines and equipment. These composites (epoxy/glass laminates) are frequently prepared from prepregs. The prepregs are made by coating woven glass fabric with an epoxy resin, usually cured to the B-stage. Dicyandiamide (DICY) is used as a curing agent for the epoxy resin. In usual conditions the curing agent is fully depleted during the curing process. However in undesirable conditions DICY crystallizes and these crystals can adversely affect insulation properties of the material. This paper deals with term specification, when the DICY crystals occur and determination of their influence on mechanical and electrical properties of epoxy/glass laminate. Based on the results is evident that the influence of residual dicyandiamide on electrical properties of epoxy/glass laminate is insignificant.