Effect of infections on the degradation of polyethylene terephthalate implants.

The macrokinetics of degradation of polyethylene terephthalate (PET) protheses removed from patients were investigated. Two types of protheses were analysed in dependance on polymer environment: 15 patients were characterized as normal, with post-operation periods of 1-10 years and 7 patients were operated at different times after implantation having a bacterial environment around the implants. The tensile strengths, surface morphology and molecular mass of these samples were compared. The macrokinetics of the PET degradation have been described. The presence of bacteria characterized by acid pH accelerates the loss of tensile strength and molecular mass in the PET corresponding to the mechanism of the polymer matrix destruction. The protheses not subjected to infection have been degraded on the surface. The experimental values of the rate constant may be used for lifetime prediction of the polymer implants in the human body under different conditions.