A prepreg which is heat curable within a temperature range of between about 200.degree. C. and 325.degree. C. comprising a reinforcing material impregnated with a curable material said curable material comprising a blend of a fluorine-containing cyanate and a fluorine-containing arylene ether polymer wherein said cyanate is a monomer having the structureN.tbd.C--O--R--[R.sup.1 ].sub.n --O--C.tbd.Nsaid fluorine containing arylene ether polymer has the structureX--R--[R.sup.1 ].sub.m --Xwherein X is any group capable of reacting with a --C.tbd.N group;R is an aliphatic or aromatic group which may or may not be fluorosubstituted;R.sup.1 is an aliphatic or aromatic group which may or may not be fluoro substituted or R.sup.1 is selected from the group consisting of ether, carbonyl, sulfone, phosphine oxide and sulfide, and at least one of R or R.sup.1 must be fluoro substituted;n is 0-10; andm is 0-100;said material in the cured state comprising a fluorine-containing polycyanurate network having a plurality of discrete phases of said fluorine-containing thermoplastic polymer dispersed therein wherein said thermoplastic polymer phases are of submicron size.