NOVELTY - Halogen-free curable composition comprises a substituted benzoxazine monomer (I); at least one epoxy resin; a catalyst comprising a phenolic compound; a toughening agent carbonyl compounds; and a solvent.    USE - The composition is useful for producing a composite article (claimed). The composition is useful: as a coating or molding in automobile, aerospace, electronic and industrial applications; in casting, laminating, impregnating, coating, adhering or gluing, painting, binding, insulating or in embedding, pressing, injection molding, extruding, sand mold binding, foam and ablative material applications; and in applications where high heat stabilities are required, e.g. in forming a composite article as a fuel cell for supplying power in conventional automobiles, hybrid cars, small boats, small-scale local power generation, household power generation, simple power supplies for isolated facilities such as camp sites and as power supplies for satellites, space development and computers.    ADVANTAGE - The composition is free of halogen, thus it provides good physical characteristics and shows improved oxidative stabilities at elevated temperatures and does not form toxic gases of combustion when exposed to fire. The composition, upon curing, provides a cured resin product having an excellent balance of mechanical and chemical properties including a high glass transition temperature, decomposition temperature, high tensile strength, low coefficient of thermal expansion, good flexibility and flame retardancy.    DETAILED DESCRIPTION - Halogen-free curable composition comprises: a substituted benzoxazine monomer of formula (I); at least one epoxy resin; a catalyst comprising a phenolic compound; carbonyl compounds of formula (R0(-X-C(=O)-Y1-R2-(OH)m)n) as a toughening agent; and a solvent.    R = phenyl (preferred), 1-8C alkyl or 3-8C cycloalkyl (all optionally substituted) or allyl;    m = 1 or 2;    n = 2-6;    R0 = n-valent radical of an elastomeric prepolymer after the removal of the terminal isocyanate, amino or hydroxyl groups, the elastomeric prepolymer being soluble or dispersible in epoxy resin; and    X, Y1 = -O- or -NR3-, where at least one X or Y1 is -NR3-;    R2 = m+1-valent radical of polyphenol or aminophenol after the removal of the phenolic hydroxyl group(s) and optionally of the amino group; and    R3 = H, 1-6C alkyl or phenol.    An INDEPENDENT CLAIM is included for a method for producing a composite article, comprising applying the halogen-free curable composition to at least one substrate and heating the substrate and the composition at a cure temperature of greater than 150 degrees C.