Abstract: Composites comprising structural fiber and matrix resin formulated from epoxys selected from the group consisting of polyglycidyl ethers of polycyclic bridged hydroxy-substituted polyaromatic compounds and N,N,N',N'-tetraglycidyl-bis(4-amino- 3-ethylphenyl)methane with from about 6 to about 150 pbw, per hundred parts by weight of the epoxy resin components, of a solid aromatic diamine hardener, toughened with porous rigid resin particles having a spheroidal spongy structure. The resulting composites exhibit surprising improvement in interlaminar strength characteristics as measured by G.sub.IC.

Abstract: Layered, fiber-reinforced composites toughened by the use of thermosetting matrix resins including rigid particles are improved in toughness when the particles are porous and have a spheroidal spongy structure, are formed of a polyamide. The method of the invention is particularly effective in improving the toughness of composites based on thermoset matrix resins, and particularly epoxy resins.

Abstract: Fiber reinforced composite structures based on epoxy resin formulations having a phase-separated or multiphase morphology when cured are effectively toughened by adding preformed carboxylated rubber particles to the matrix resin prior to curing the composite.

Abstract: Layered, fiber-reinforced composites are toughened by the use of thermosetting matrix resins including polyphenylene ether particles. The method of the invention is particularly effective in improving the toughness of composites based on thermoset matrix resins.

Abstract: Preformed carboxylated rubber particles are effective for toughening fiber reinforced composite structures based on thermoset resins such as epoxy resin formulations. The composites are effectively toughened by adding the carboxylated rubber particles to the matrix resin prior to curing the composite.

Abstract: Preformed carboxylated rubber particles are effective for toughening fiber reinforced composite structures based on thermoset resins such as epoxy resin formulations. The composites are effectively toughened by adding the carboxylated rubber particles to the matrix resin prior to curing the composite.

Abstract: Fiber-reinforced compositions comprising a structural fiber and a cyanate ester resin formulation having an N-substituted urea compound as a latent cure accelerator provide rapid-curing prepreg with good out-time characteristics. The prepreg may be used to form composite articles with good toughness and excellent retention of properties on extended exposure to moisture at elevated temperatures.

Abstract: Urea compounds having a plurality of substituents selected from hydrogen, substituted hydrocarbyl radicals and unsubstituted hydrocarbyl radicals are good latent cure accelerators for thermosetting cyanate resin formulations. The resulting cyanate resin formulations are useful as coatings, adhesives and as impregnating resins, particularly in applications where extended storage at or near room temperature is desired.

Abstract: Novel tetraglycidates have the formula ##STR1## wherein R.sup.1 and R.sup.2 are independently hydrogen, alkyl of 1 to 8 carbon atoms, perfluoroalkyl, or cycloalkylidene of 5 to 7 carbon atoms. Epoxy resin systems exhibiting good tensile properties and moisture sensitivity can be made by copolymerizing the tetraglycidates with a polyamine curing agent. Prepregs can be made by combining the epoxy resin systems with a fiber reinforcement. The epoxy resin system may include a co-epoxide.

Abstract: Novel 3-ring tetraglycidates having the formula ##STR1## wherein ##STR2## Y=halogen, C.sub.1 -C.sub.4 alkyl; and n=0 to 4, are disclosed.Epoxy resin systems exhibiting good tensile properties and moisture sensitivity can be made by copolymerizing the tetraglycidates with a polyamine curing agent. Prepregs can be made by combining the epoxy resin systems with a fiber reinforcement. The epoxy resin system may include a co-epoxide.

Abstract: Urea compounds having a plurality of substituents selected from hydrogen, substituted hydrocarbyl radicals and unsubstituted hydrocarbyl radicals are good latent cure accelerators for thermosetting cyanate resin formulations. The resulting cyanate resin formulations are useful as coatings, adhesives and as impregnating resins, particularly in applications where extended storage at or near room temperature is desired.

Abstract: Novel tetraglycidates have the formula ##STR1## wherein R.sup.1 and R.sup.2 are independently hydrogen, alkyl of 1 to 8 carbon atoms, perfluoroalkyl, or cycloalkylidene of 5 to 7 carbon atoms. Epoxy resin systems exhibiting good tensile properties and moisture sensitivity can be made by copolymerizing the tetraglycidates with a polyamine curing agent. Prepregs can be made by combining the epoxy resin systems with a fiber reinforcement. The epoxy resin system may include a co-epoxide.

Abstract: Novel 3-ring tetraglycidates having the formula ##STR1## wherein X=O, S, ##STR2## --CH.sub.2 --, C.dbd.O; Y=halogen, C.sub.1 -C.sub.4 alkyl; and p0 n=0 to 4, are disclosedEpoxy resin systems exhibiting good tensile properties and moisture sensitivity can be made by copolymerizing the tetraglycidates with a polyamine curing agent. Prepregs can be made by combining the epoxy resin systems with a fiber reinforcement. The epoxy resin system may include a co-epoxide.