Amphiphilic block copolymer-toughened epoxy resins and electrical laminates made therefrom

A process for preparing a curable laminate epoxy resin varnish composition comprising mixing

• (a) an epoxy resin;
• (b) an amphiphilic block copolymer containing at least one epoxy resin miscible block segment and at least one epoxy resin immiscible block segment;
• wherein the immiscible block segment comprises at least one polyether structure provided that the polyether structure of said immiscible block segment contains at least one or more alkylene oxide monomer units having at least four carbon atoms;
• wherein the miscible block segment comprises at least one polyether structure;
• and wherein the composition of the amphiphilic block copolymer ranges from 90 percent epoxy resin miscible segments of the amphiphilic block copolymer and 10 percent epoxy resin immiscible segments of the amphiphilic block copolymer to 10 percent epoxy resin miscible segments of the amphiphilic block copolymer and 90 percent epoxy resin immiscible segments of the amphiphilic block copolymer;
• such that when the epoxy resin composition is cured, the toughness, G1c, as measured by the fracture toughness test ASTM D5528, of the resulting cured epoxy resin composition is increased by a factor of 1.5 times to 2.5 times that of a cured laminate epoxy resin composition without the amphiphilic block copolymer;
• (c) a curing agent;
• (d) a curing catalyst;
• and
• (e) a solvent.