US Patent 10173108 Golf club head comprising microscopic bubble material

A golf club head with at least one cavity including a weight that is co-molded with a fill material comprising a polymer and a plurality of microscopic bubbles, and methods of manufacturing such golf club heads, are disclosed herein. The plurality of microscopic bubbles constitutes at 5-70% of the volume of the fill material, and more preferably approximately 20-30% of the volume of the fill material. The polymer material preferably is a polyurethane having a Poisson's ratio of 0.40-0.50. The weight is preferably composed of a metal alloy with a density greater than 4 g/cc, such as steel or tungsten alloy.