The present invention relates to novel adhesive-forming compositions of silylated polyurethane prepolymer blended with pre-formed adhesives, and pressure sensitive adhesives containing the same. The silylated polyurethane prepolymer is obtained from the silylation of a polyurethane prepolymer derived from the reaction of polybutadiene polyol and polyisocyanante, where the polybutadiene polyol possesses a primary hydroxyl group content of from about 0.1 to about 2.0 meq/g.