Polyurethane prepolymers having little or no plasticizer and their use in vehicular glass adhesives

An isocyanate terminated polyether prepolymer comprising a polyisocyanate reaction product of a polyisocyanate having an isocyanate functionality of about 2.2 to 2.7 with a polyether monol having an average molecular weight (Mw) of 1000 to 2000 g/moles and a polyol to form the isocyanate prepolymer, the polyol and monol having an overall hydroxyl functionality that is from 1 to 3, and the polyol being comprised of a diol having an average molecular weight (Mw) of 500 to 8,000 grams/mole and a triol having an average molecular weight (Mw) of 1500 to 4500 grams/mole;

• wherein the monol is present in an amount from 40% to 60% of the hydroxyl groups in the polyol and monol, the diol is present in an amount from 5% to 35% of the hydroxyl groups present in the polyol and monol and the triol is present in an amount from 10% to 40% of the hydroxyl groups present in the polyol and monol and the isocyanate index is from 1.1 to 2.2;
• and said prepolymer having:
• (i) a weight molecular weight average (Mw) of about 2000 to about 30,000 g/mole, (ii) a free isocyanate content of 0.8% to 4% by weight of said prepolymer, and (iii) viscosity of 1000 to 50,000 centipoises.