ADHESION MECHANISMS OF POLYURETHANES TO GLASS SURFACES .2. PHASE-SEPARATION IN POLYURETHANES AND ITS EFFECTS ON ADHESION TO GLASS

Polyurethanes were prepared from different molecular weight polycaprol actone-based polyols with varying amounts of hard segment made with to luene diisocyanate and butanediol. A theoretical model based on hard a nd soft segment miscibility was used to predict phase separation in th ese polyurethanes. Wide-angle X-ray diffraction, near-infrared spectro scopy, and Fourier transform infrared spectroscopy were used to determ ine phase separation. Good agreement was found between the experimenta l results and the theoretical predictions. The glass surfaces of the p reviously tested glass/polyurethane adhesion samples were analyzed by angular dependent X-ray photoelectron spectroscopy (ADXPS). ADXPS data revealed an interphase region of approximately 2-10 nm in thickness p resent between the polyurethane matrix and the glass substrate in each sample. The data also showed that the composition of the interphase r egion was influenced not only by the matrix composition, but also by t he phase separation. The curve-fitted C 1s spectra of the interphase r egion showed the presence of C-O type linkages that could be due to th e presence of C-OH from the polyols and/or the butanediols, and C-O-Si type bonds. These observations were supported by the adhesion results of various polyurethanes to glass test coupons primed with a 2% solut ion of butanediol in acetone.