Rigid polyurethane foam

A method of forming a composite article comprising a substrate and a rigid polyurethane foam, said method including the steps of:

• (A) providing an isocyanate reactive component comprising;
• (i) an aromatic polyester polyol;
• (ii) a rigid polyol;
• and
• (iii) an aliphatic polyester polyol;
• wherein the aliphatic polyester polyol is present in the isocyanate reactive component in an amount of from 2 to 10 parts by weight, based on 100 parts by weight of the total weight of the polyols present in the isocyanate reactive component;
• (B) providing an isocyanate;
• (C) providing a blowing agent;
• (D) combining the isocyanate reactive component and the isocyanate in the presence of the blowing agent to form a reaction mixture;
• and
• (E) applying the reaction mixture to the substrate having a substrate temperature of greater than 41° C. (105° F.) to form the rigid polyurethane foam and the composite article comprising the substrate and the rigid polyurethane foam;
• wherein the rigid polyurethane foam has a tensile adhesion of greater than 35 kPa (5 psi) when disposed on a metal substrate, a polyester coated metal substrate, a polyurethane coated metal substrate, or an epoxy coated metal substrate, each having a substrate temperature of greater than 41° C. (105° F.), and tested in accordance with ASTM D1623-09.

A polyurethane system for use in forming a composite article which comprises a substrate and a rigid polyurethane foam, said polyurethane system comprising:

• (A) an isocyanate reactive component comprising;
• (i) an aromatic polyester polyol;
• (ii) a rigid polyol;
• and
• (iii) an aliphatic polyester polyol;
• wherein said aliphatic polyester polyol is present in said isocyanate reactive component in an amount of from 2 to 10 parts by weight, based on 100 parts by weight of the total weight of said polyols present in said isocyanate reactive component;
• and
• (B) an isocyanate;
• in the presence of
• (C) a blowing agent;
• wherein said rigid polyurethane foam has a tensile adhesion of greater than 35 kPa (5 psi) when disposed on a metal substrate, a polyester coated metal substrate, a polyurethane coated metal substrate, or an epoxy coated metal substrate, each having a substrate temperature of greater than 41° C. (105° F.), and tested in accordance with ASTM D1623-09.