Hybrid polyurethane spray foams made with urethane prepolymers and rheology modifiers

A two-part spray foam system for forming a hybrid non-isocyanate polyurethane foam, the foam system comprising:

• a first part comprising:
• a non-isocyanate polyurethane reactant comprising a preformed urethane prepolymer;
• and
• a resin polymer;
• a second part comprising:
• a cross-linker having at least two reactive functional groups adapted to be rapidly crosslinked with the reactive functional groups of the urethane reactant to form a hybrid polyurethane;
• and
• a blowing agent;
• and
• 0.1% to 20% by weight of a rheology modifier provided in at least one of the first part and the second part, based on the weight of the hybrid non-isocyanate polyurethane foam.

A method of forming a non-structural, non-isocyanate foam with reduced harmful vapor emission from a two-part spray foam system, the method comprising:

• providing, in a first spray foam part, a urethane reactant comprising a cyclocarbonate-amine adduct and
• a resin polymer;
• providing, in a second spray foam part, a cross-linker having at least two reactive functional groups adapted to be rapidly crosslinked with the reactive functional groups of the urethane reactant to form a hybrid non-isocyanate polyurethane foam and a blowing agent;
• and a rheology modifier in at least one of the first spray foam part and the second spray foam part;
• mixing the first spray foam part and the second spray foam part;
• applying the non-structural foam to a substrate, wherein the foam is tack-free within two minutes after mixing and cures to form a non-structural, non-isocyanate foam having an R-value of greater than 3.