Composite structure, a resin composition for use in the composite structure, and a process for making the same

A resin component for reacting with an isocyanate component at ambient temperature, said resin component comprising:

• (A) an isocyanate-reactive component having a nominal functionality of at least 3;
• (B) an imidazole-based catalyst active at ambient temperature that initiates an exothermic reaction between the isocyanate component and said isocyanate-reactive component and establishes a reaction temperature greater than ambient temperature;
• and
• (C) a temperature-activated catalyst different from said imidazole-based catalyst that is activated at the reaction temperature established by said imidazole-based catalyst.

A process for making a composite structure comprising the steps of:

• (A) providing a first layer comprising a styrenated unsaturated polyester wherein the first layer is a show surface of the composite structure;
• and
• (B) providing a second layer comprising the reaction product of:
• (I) an isocyanate component;
• and
• (II) a resin component reactive with the isocyanate component at ambient temperature comprising:
• (a) an isocyanate-reactive component having a nominal functionality of at least 3;
• (b) an imidazole-based catalyst active at ambient temperature;
• and
• (c) a temperature-activated catalyst different from the imidazole-based catalyst;
• wherein the imidazole-based catalyst initiates an exothermic reaction between the isocyanate component and the isocyanate-reactive component and establishes a reaction temperature greater than ambient temperature and wherein the temperature-activated catalyst is activated at the reaction temperature established by the imidazole-based catalyst to complete a cure of the second layer.