Benzoxazine resin composition, prepreg, and fiber-reinforced composite material

A curable benzoxazine resin composition comprised of at least a component [A], a component [B], component [C] and a component [D], wherein:

• a) the component [A] is comprised of at least one benzoxazine of Formula (IA):
• wherein Z is selected from C═O, CH2OC(═O), O, S, S═O, or O═S═O, each R is independently selected from hydrogen, a C1-C20 alkyl group, an allyl group, or a C6-C14 aryl group, and each R1 is independently selected from hydrogen, a C1-C20 alkyl group, an allyl group, or a C6-C14 aryl group;
• b) the component [B] is comprised of at least one benzoxazine of Formula (IA′) and/or Formula (IB′):
• wherein n is 0 or 1;
• if n=1, Z′ is selected from a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted divalent C6-C20 aryl group, or a substituted or unsubstituted divalent C2-C20 heteroaryl group;
• and if n=0, the benzyl groups of the benzoxazine moieties are fused or connected by a direct bond between the two benzoxazine moieties;
• where L is selected from a divalent hydrocarbon linkage group such as CH2, C(CH3)2, CH(CH3), dicyclopentadiene, Ar, and Ar—Y—Ar, where Y may be a direct bond C(R2)(R3), C(R2)(Ar), a divalent heterocycle, [C(R2)(R3)]x—Ar—[C(R4)(R5)]y S, SO2, and O, where Ar is an aryl group. R2, R3, R4, and R5 are independently selected from H, C1-C8alkyl and halogenated alkyl;
• c) the component [C] is comprised of at least one cycloaliphatic epoxy resin represented by Formula (II):
• wherein m=0 or 1;
• R6 and R7 are the same or different and are each a substituted or an unsubstituted C1-C20 aliphatic moiety which together with carbon atoms of an epoxy group form at least one aliphatic ring, wherein m is 0 or 1;
• when m=1, X represents a single bond, two single bonds or, a divalent moiety;
• wherein when m=0, the aliphatic rings are fused which include R6 and R7 (that is, a fused ring system is present which involves R6 and R7);
• d) the component [D] comprises a thermoplastic compound comprising one or more repeating units, wherein the thermoplastic compound is a polyethersulfone or polyimide;
• and
• e) the component [A] and the component [B] are present in the curable benzoxazine resin composition in a mass ratio [A]/[B] of between 1/2 and 5/1 inclusive and component [A], component [B] and component [C] are present in a mass ratio [C]/([A]+[B]) of between 1/9 and 2/3 inclusive.