| abstract |
Golf balls having an inner core made of a foamed composition are provided. The core assembly preferably includes a foam inner core (center) and surrounding outer core layer. A cross-linked thermoplastic, preferably an ethylene acid copolymer ionomer, is used to form the foam composition. The core layers have different hardness gradients and specific gravity values. The ethylene acid copolymer is reacted with a metallic acrylate salt and peroxide free-radical initiator to form the cross-linked polymer. The foamed, cross-linked composition helps provide the inner core with good resiliency, thermal stability, and durability. Non-foamed thermoplastics or thermosets such as polybutadiene rubber may be used to form the outer core layer. The ball further includes a cover that may be multi-layered. |