ABSTRACT
Polyurethanes are used in a variety of structural applications as adhesives to glass surfaces. A systematic experimental plan was conducted in which a segmented polyurethane system (caprolactone based polyols + toluene diisocyanate + 1,4-butanediol) with variations in hard and soft segment contents was bonded to the air side of float glass surfaces. Practical adhesion measurements showed that the structure of the interphase, in particular phase separation, played a predominant role in affecting the adhesion. Polyurethanes with higher modulus showed better practical adhesion than lower modulus formulations but those that had the greater degree of phase separation had superior adhesion to the glass. Analytical investigation of the failure surfaces indicated that covalent chemical bonding did not occur between the polyurethanes and the glass but hydrogen bonding through a butanediol-rich interphase layer was the dominant mechanism. When the practical adhesion values of all the polyurethane systems to glass were compared, a linear relationship between the polar component of the surface free energy of the polyurethanes and the adhesion level was found.
