Patent ID: 8353960

Claim:
A process for making a polymeric product having a gradual variation in modulus through at least a portion of the product, comprising the steps of: (a) reacting at least one of a multifunctional isocyanate, a polyol and a chain extender, wherein at least two reagents selected from the isocyanate, the polyol, the chain extender, any mixture thereof and any pre-polymer formed therefrom, are intensively mixed to form a first polyurethane having a predetermined stoichiometry and thermal history; (b) reacting at least one of a multifunctional isocyanate, a polyol and a chain extender, wherein at least two reagents selected from the isocyanate, the polyol, the chain extender, any mixture thereof and any pre-polymer formed therefrom, are intensively mixed to form a second polyurethane having a predetermined stoichiometry and thermal history which is different to the stoichiometry and thermal history of the first polyurethane; and (c) injecting the first and second polyurethanes into a mould defining the polymeric product before the polymerization reactions associated with the production of the first and second polyurethanes are complete so that polymerization reactions between the first and second polyurethanes occur in the mould to form a region of polyurethane having a gradual variation in modulus, wherein the region extends through at least a portion of the product.