Abstract: A novel bis-imide matrix resin system especially useful for high temperature, high performance, graphite fiber composites is disclosed. Microcracking of composites is reduced and transverse strength is increased by the addition to the resin system of 1 to 15 percent of compatible elastomers, such as polyether sulfones, bis-phenol linear homopolymeric epoxies or polyacrylic esters. The resin system comprises 50 to 95 percent by weight of ethylenically unsaturated bis-imides, preferably a low melting mixture of a major portion of maleimides of aromatic amines with a minor portion of maleimides of an aliphatic amine and 5 percent to 35 percent by weight of a diunsaturated low-temperature cross-linking agent such as divinyl benzene which gels the bis-imide at low temperatures. Room temperature tackiness, heat resistance and cross-link density are improved by the presence of 1 to 10 percent of a trifunctional curing agent.

Abstract: A novel bis-imide matrix resin system comprising 50 to 95 percent by weight of ethylenically unsaturated bis-imides, preferably a low melting mixture of a major portion of maleimides of aromatic amines such as toluene diamine and methylene dianiline with a minor portion of maleimide of an aliphatic amine such as trimethyl hexamethylene diamine and 5 percent to 35 percent by weight of a diunsaturated low-temperature cross-linking agent such as divinyl benzene which gels the bis-imide at low temperatures. This reduces stress between the matrix resin and the surface of the reinforcing fiber, thus reducing the tendency to form microcracks. Room temperature stability is improved by the presence of 0.5 to 5 percent of an oxidation inhibitor such as hydroquinone. The resin is useful as a matrix resin for high performance, graphite fiber reinforced composites.CROSS REFERENCE TO RELATED APPLICATIONThis application is a continuation of Ser. No. 248,978, filed Mar. 30, 1981, now U.S. Pat. No.

Abstract: Reinforcement fiber for fiber-reinforced resin composites such as graphite tows are spliced by applying a solution of a linear, soluble, high glass transition temperature polyimide having good thermal-oxidative stability to the broken ends of a fiber, placing the ends in contact and removing solvent. The preferred polyimide is an aromatic-cycloaliphatic diamine such as 5,(6)-amino-1-(4' amino phenyl)-1,3-trimethylindane (DAPI) imidized with a dianhydride such as PMDA or BTDA. The soluble polyimide can be preapplied to the fiber as a sizing. The splices are not apparent by visual inspection nor by instrumental scanning of cured composites indicating there is no blistering nor loss of strength.

Abstract: A novel bis-imide matrix resin system comprising 50 to 95 percent by weight of ethylenically unsaturated bis-imides, preferably a low melting mixture of a major portion of maleimides of aromatic amines with a minor portion of maleimide of an aliphatic amine and 5 percent to 35 percent by weight of a diunsaturated low-temperature cross-linking agent such as divinyl benzene which gels the bis-imide at low temperatures. This reduces stress between the matrix resin and the surface of the reinforcing fiber, thus reducing the tendency to form microcracks. Microcracking is further reduced and transverse strength is increased by the addition of 0 to 15% of compatible elastomers to the resin and cross-linking agent. Room temperature tackiness, heat resistance and cross-link density are improved by the presence of 0 to 10% of a trifunctional curing agent.

Abstract: A novel bis-imide matrix resin system comprising 50 to 95 percent by weight of ethylenically unsaturated bis-imides, preferably a low melting mixture of a major portion of maleimides of aromatic amines with a minor portion of maleimide of an aliphatic amine and 5 percent to 35 percent by weight of a diunsaturated low-temperature cross-linking agent such as divinyl benzene which gels the bis-imide at low temperatures. This reduces stress between the matrix resin and the surface of the reinforcing fiber, thus reducing the tendency to form microcracks. Microcracking is further reduced and transverse strength is increased by the addition of 0 to 15% of compatible elastomers to the resin and cross-linking agent. Room temperature tackiness, heat resistance and cross-link density are improved by the presence of 0 to 10% of a trifunctional curing agent.