Biodegradable tennis balls are described. A biodegradable tennis ball includes a core forming a hollow interior chamber, the core made of a blend of a rubber based material, a first petroleum based material, and a first biodegradable additive. The biodegradable tennis ball also includes a felt layer overlaying a surface of the core, the felt layer made of a second blend of a second petroleum based material and a second biodegradable additive. In some cases, the biodegradable tennis ball may include an adhesive layer adhering the felt layer to the core. In some cases, the felt layer may further include wool.

An adhesive for a tennis ball of the present disclosure includes base rubber and a filler. The base rubber contains, as a main component thereof, liquid rubber having a number average molecular weight of not less than 10,000. The filler has an average nitrogen specific surface area of not less than 40 m.sup.2/g. A tennis ball of the present disclosure includes a hollow core made of a rubber material. The core includes two hemispherical half cores. The two half cores are adhered to each other by using the adhesive for a tennis ball.

A tennis ball may include a non-foamed thermoplastic core defining an internal volume, the core having an outer meltable surface. The core may include a thermoplastic material having a specific gravity of 0.86 to 1.38, a flexural modulus of 2.0 to 50.0 MPa, and a Shore D hardness of 10 to 70. The thickness of the thermoplastic material may be between 3.0 and 8.0 mm and configured to maintain dimensional stability at internal pressures of between zero and 15 psi. The tennis ball may further include a felt cover at least partially covering the core, wherein the tennis ball conforms to ITF and USTA size, weight, deformation and rebound requirements.