The hydrolytic degradation of polyurethanes

The hydrolytic degradation of poly(ester)‐urethanes (PUR) has been studied by viscometry of solutions of films that were treated for various times with water of fixed temperature. On the basis of some simplifying assumptions a general expression was derived relating the decay of the limiting viscosity number (LVN) upon hydrolysis to the reaction rate constant of the hydrolysis reaction. For a homologous series of polymers, with decreasing molecular weight that eventually resulted from the measurements of the hydrolysis, the relation mechanical property versus molecular weight was obtained for four mechanical properties. These relations were interpreted in terms as described previously by Flory and many others. The mechanical properties of hydrolyzed films and those of redissolved and recast hydrolyzed films were compared and showed some interesting features.