Abstract: This disclosure addresses resin systems which contain thermosetting materials and thermoplastic modifiers, the resin systems being formed by dispersing particles of thermoplastic solids in the thermosetting materials, the particles being soluble in the resins at temperatures below the resin system gelation temperature. According to this disclosure, the systems are improved by the use of a blend of two types of thermoplastic material--a high glass transition temperature thermoplastic such as a poly(benzophenone-imide) and a high toughness thermoplastic such as a poly(ether-imide). By appropriate adjustment of the relative amounts of these two thermoplastics, resin system properties such as toughness, service temperature, thermal stability and solvent resistance can be adjusted to optimum levels.

Abstract: Thermosetting resins for use in high performance fiber-reinforced composites are toughened without compromising their processability by the inclusion of micron-sized particles of thermoplastic material which are solid at ambient temperatures but solubilize in the resins at a temperature below the gel temperature of the thermosetting resin. By appropriate selection of the solubilization temperature (or temperature range) of the thermoplastic material, one achieves a composite product having intralaminar or interlaminar toughness emphasized or a combination of both. The invention is of particular utility when applied to bismaleimide resin systems.