Lifetime Prediction of High Tenacity Polyester Yarns for Hydrolytic Degradation Used for Soil Reinforcement

The long-term strength is considered the various degradation mechanisms in the design of the reinforced soil structure so that ISO TR 20432 provides guidelines for the determination of the long-term strength of geosynthetics for soil reinforcement. Geosynthetics using polyester and polyamide are susceptible to hydrolytic degradation due to ester and amide group by condensation polymerization. In this study, the accelerated hydrolysis test was carried out to predict service lifetimes of polyester filament yarns which are widely used in geosynthetics for soil reinforcement. Two types of filament yarns with different carboxyl end groups (CEG) were immersed in distilled water at elevated temperature at 80, 90 and 95 °C up to 112 days for shortening the test times. The reduction in tensile strengths was evaluated as the rate of hydrolytic degradation along the time at each temperature. The failure times were estimated to reach 50, 60, 70, 80, 90 % of retained tensile strengths by linear regression using time as an independent variable and retained strength as a response variable. The service lifetimes of polyester filament yarns were predicted at service temperature using Arrhenius relation of failure times and temperatures. The service lifetimes of both polyester yarns are exceeding 100 years up to 80 % of retained strength at 20 °C of service temperature. This can provide guidance to designers and manufacturers of geosynthetics in calculating the specific reduction factor of hydrolytic degradation at 100 years of design lifetime.