Types of elastomeric modifiers

Rubber toughened epoxy formulations do offer excellent fracture properties [76-81]. 

However, the presence of the rubber phase can decrease the modulus and thermal stability, while at the same time increasing the water absorption which causes loss of properties at elevated temperatures. 

These tougheners can be physically blended into an epoxy resin system or can be capped with an epoxy resin by pre-reaction and then blended with unmodified epoxies and cure agents, usually using triphenyl phosphine as a catalyst system, which promotes the carboxyl-epoxy reaction at temperatures under 120°C [82]. 

Finaprene, solution polymerized butadiene, butadiene/styrene elastomers, as random and deblock copolymers, are available from Fina Chemicals [83]. 

Polyvinyl butyral derived from polyvinyl alcohol and butyraldehyde can be added to epoxy and phenolic resins to improve impact resistance and peel strength. 

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