CURE SHRINKAGE DEFECTS IN EPOXY-RESINS

The formation of shrinkage defects in eight epoxy compositions was inv estigated during isothermal cure in a constraining vessel. For an epox y resin there may be three ranges of isothermal cure temperatures dist inguished by the type of cohesive defects formed. The boundaries of th e ranges are individual for each polymer. The mechanisms of shrinkage damage and type of defects are defined initially by gelation and vitri fication processes. Dependence of the processes upon temperature leads to a dramatic change in the influence of the type of defect formation and defines the boundaries of the temperature ranges. The quantity of cohesive defects depends on temperature range to a large extent and p olymer chemical composition to a lesser extent. Vitrification may be t he cause of shrinkage defect formation in both network and linear poly mers.