| Résumé : |
These studies examine the effect of substrate surface tension on crosslinking reactions in waterborne polyurethanes (PUR) applied to tin-plated steel, steel, polypropylene (PP), thermoplastic olefin (TPO), and glass. The results show that, relative to tin-plated steel, removal of tin-plating from a steel substrate increases isocyanate (NCO) consumption by 42% near the film-substrate (F-S) interface. When PUR is allowed to crosslink on steel, PP, TPO, and glass, the NCO concentration is greater at the film-air (F-A) interface. Furthermore, crosslinking reactions result in a greater amount of urea-hydrogen bonded species near the F-S interface for all substrates. While an increase ofsubstrate surface tension decreases the amount of urea-hydrogen bonded carbonyl groups near the F-S interface, TPO was found to exhibit different behavior due to talc stratification near the surface. In this case, the presence of talc in WB-PUR coatings or thermoplastic substrates decreases the amount of hydrogen-bonded species and increases NCO consumption. |
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Interfacial studies of crosslinked urethanes : part IV. Substrate effect on film formation in polyester waterborne polyurethanes in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 71, N° 896 (09/1999)
