Windmill propeller blade and method of making same

A windmill blade which comprises reinforcing fibers in a resin matrix, wherein the matrix is made from a matrix composition which comprises (a) one or more epoxy resins, (b) one or more reactive diluents, and (c) at least one amphiphilic block copolymer which comprises at least two different polyether blocks and is present in the composition in an amount of from about 0.5% to about 10% by volume, based on a total volume of the matrix composition;

• wherein the amphiphilic block copolymer, component (c), comprises at least one polyether block A and at least one polyether block B;
• wherein the polyether block A is independently selected from a polybutylene oxide block, a polyhexylene oxide block, a polydodecylene oxide block, and a polyhexadecylene oxide block;
• and
• wherein the polyether block B is independently selected from a polyethylene oxide block, a polypropylene oxide block, and a poly(ethylene oxide-co-propylene oxide) block;
• wherein a weight ratio of the polyether block A to the polyether block B in the amphiphilic block copolymer, component (c), is from about 10:1 to about 1:10;
• wherein the epoxy resin, component (a), is present in an amount of from about 30% to about 95% by volume, based on the total volume of the matrix composition;
• wherein the reactive diluent, component (b), is present in an amount of from about 5% to about 25% by volume, based on the total volume of the matrix composition;
• and
• wherein the amphiphilic block copolymer, component (c), is present an amount of from about 1% by volume to about 5% by volume, based on the total volume of the matrix composition.