Heat-Resistant Carbon Fiber Reinforced Plastics Based on a Copolymer of Bisphthalonitriles and Bisbenzonitrile

New phthalonitrile resins that provide processing properties at the level of epoxy resins and composites obtained from them are discussed. The processing parameters of the resins are improved due to the discovery of reactive diluents based on bisbenzonitriles. By introducing these comonomers into the resin composition the melt viscosity is reduced to less than 100 MPa s at a temperature of 120°C, which allows one to obtain carbon fibers by modern injection techniques. The curing programs of the composite are selected in order to attain the maximum compressive strength (852 MPa). Carbon fiber reinforced plastics postcured at 375°C retain up to 90% of their mechanical properties at 400°C (τ12 = 60–80 MPa). It is first shown that prepregs can be produced from phthalonitrile resins using the melt technology and composites from them can be obtained by hot pressing. Carbon fibers possess high limiting oxygen index values (LOI > 80%). Thus, phthalonitrile resins and prepregs are developed for non-autoclave processing of carbon and glass composites suitable for operation at elevated temperatures.