A variety of polymers, both thermosets as well as thermoplastics, can be blended and co-reacted with epoxy resins to provide for a specific set of desired properties. The most common of these are nitrile, phenolic, nylon, polysulfide, and polyurethane resins. At high levels of additions these additives result in hybrid or alloyed systems with epoxy resins rather than just modifiers. They differ from reactive diluents in that they are higher molecular weight materials, are used at higher concentrations, and generally have less deleterious effect on the cured properties of the epoxy resin.
These hybrid epoxy adhesives are generally used for demanding structural applications such as in the aerospace industry where the optimal properties from each component are desired. For example, epoxy is generally used to provide good adhesion and processing characteristics. They are blended with the following resins to provide additional improvements in the properties noted.
Hybrid resins have been used to improve flexibility, thermal shock resistance, elongation, heat distortion temperature, and impact strength of epoxy adhesives.