The effect of chemical structure on thermal, hydrolytic, and solvent resistance of polyurethane films

Abstract A study of the resistance of polyurethane films to various swelling and degrading environments was carried out. Physical properties of the resulting polymers were correlated with chemical variations in the polyether and isocyanate structures. Thermal resistance was determined by various techniques, including differential thermal analysis, thermogravimetric analysis, and heat aging. High crosslink density and the use of polyisocyanates of high aromatic content resulted in increased thermal stability. Resistance to moisture at high temperatures was also found to increase with crosslink density; it was influenced by the type of polyol and isocyanate used in the urethane reaction. Solvent resistance of polyurethane structures increased at higher crosslink densities, appeared to be unaffected by the type of aromatic diisocyanate, and was reduced with the use of a large excess of isocyanate. The ultraviolet resistance of films prepared from various isocyanates decreased in the order: tolylene diisocyanate (TDI) > polyphenyl polymethylene polyisocyanate (PAPI) > xylylene diisocyanate (XDI).