The hydrolytic stability of Mitrathane (a polyurethane urea)--an x-ray photoelectron spectroscopy study

The hydrolytic stability of microporous Mitrathane polyetherurethane urea vascular prostheses has been evaluated at pH 7 and pH 9, at 37 degrees, 60 degrees, and 80 degrees C for time periods of up to 968 days. Mechanical strength was evaluated using a hydrodynamic burst test and surface chemical changes by x-ray photoelectron spectroscopy. The samples held at 80 degrees C showed the greatest mechanical strength loss which corresponded to the hydrolysis of the urethane groups. It was concluded that the gross in vivo surface degradation of Mitrathane prostheses, observed after six months, could not have been caused by simple chemical hydrolysis alone, as the polymer was found to be stable at 37 degrees C for at least 11 months.