Comparison of Epoxy/Rubber Blends with Other Toughening Strategies: Thermoplastic and Hyperbranched Modifiers

epoxy resins need to be toughened to comply with structural application requirements. The first successful toughened thermosets were modified by the addition of liquid reactive rubbers. This approach led to most of the commercial systems for advanced composites and adhesive systems in use today. More demanding requirements for thermal and solvent resistance led to the development of alternative toughening approaches. Aromatic thermoplastics were particularly successful in achieving good results in terms of toughness, thermal, and solvent resistance. Recently, increasing interest in liquid molding technologies led to the development of epoxy blends with low viscosity and good toughness. Epoxy/hyperbranched blends were developed as liquid molding systems. However, some novel approaches based on the use of soluble thermoplastic films or fibers have been developed that can outperform hyperbranched toughening. The present chapter addresses the comparison of epoxy/rubber blends with other toughening strategies such as thermoplastic and hyperbranched polymers. Formulations suitable for liquid molding are also discussed.