Abstract: Multi-piece golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) comprising a foam composition, preferably foamed polyurethane. The outer core layer is preferably formed from a non-foamed thermoset composition such as polybutadiene rubber. Preferably, the specific gravity (density) of the foam inner core is less than the density of the outer core layer. The ball further includes a cover of at least one layer and may include at least one casing layer. The core structure and resulting ball have relatively good resiliency.

Abstract: Multi-piece golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) comprising a foam composition, preferably foamed polyurethane. The outer core layer is preferably formed from a non-foamed thermoset composition such as polybutadiene rubber. Preferably, the specific gravity (density) of the foam inner core is less than the density of the outer core layer. The ball further includes a cover of at least one layer and may include at least one casing layer. The core structure and resulting ball have relatively good resiliency.

Abstract: Golf balls having a dual-core comprising an inner core and outer moisture barrier core layer are provided. The outer core help prevent moisture from penetrating into the inner core. A cover layer, preferably made of a polyurethane or polyurea material, is disposed about the outer core layer. The inner and outer cores are formed of a rubber composition, preferably a polyalkenamer rubber. The polyalkenamer rubber composition may further include other rubbers such as polybutadiene, polyisoprene, ethylene propylene rubber, ethylene propylene diene rubber, and styrene-butadiene rubber. The outer core has a moisture vapor transmission rate (MVTR) lower than that of the cover. In one version, the outer core has a MVTR of 1 grams·mm/m2·day or less, preferably in the range of 0.45 to 0.95 grams·mm/m2·day.