Abstract
The relationships among the tensile strength, molecular weight and amount of end -COOH group of poly (butylene terephthalate) [PBT] were obtained during degradation process. The tensile strengt h became constant up to a certain time and then decreased sharply. This break point depended on the temperature and humidity. The logarithmic molecular weight decreased linearly and amount of -COOH group increased with time, depending on the degradation conditions. When the tensile strength is plotted against the molecular weight or amount of the COOH, the unequivocal relationships are obtained independent of the degradation conditions. The break points are observed where the tensile strength starts to drop sharply. Plotting amount of -COOH group against the logarithmic molecular weight, the straight relationships have also the break points. These results indicate that the degradation process can be evaluated by measuring amount of -COOH group and the molecular weight using only small amount of samples.
