Rubber-toughened epoxy adhesives material properties

Adhesives based solely on epoxy resins and amine curing agents give cross-linked materials that have high modulus but are very brittle and have no resistance to peel forces. Epoxy resins became much more useful when it was found that rubber flexibilizers could be added to increase crack resistance. Further, it was found that under appropriate reaction conditions, these rubbers could act to "toughen" the epoxy system. That is, addition of rubber flexibilizers tends to reduce the Tg and shear properties of an epoxy. When an epoxy is "toughened" little or no change occurs in the Tg and shear properties while a substantial increase in... 

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