Cross-linked thermoplastic polyurethane/polyurea and method of making same

A method for forming a golf ball layer composed of a cross-linked thermoplastic polymer, the method comprising:

• mixing a thermoplastic urethane based resin material and 4, 4′ diphenylmethane di-isocyanate to create a first mixture, the 4, 4′ diphenylmethane di-isocyanate comprising between 1% to 10% of the total mass of the mixture;
• heating the mixture to a temperature within the range of 250° F. to 550° F. to create a heated mixture;
• injecting the heated mixture into a barrel of an injection molding machine through a first opening;
• injecting a reaction product into at least one injection mold cavity, the reaction product formed by the reaction of the heated mixture and a liquid mixture;
• and
• forming a golf ball layer composed of the reaction product.