"Lifetime Prediction of Polyolefin Geosynthetics Utilizing Acceleration Tests Based on Temperature and Pressure"
Geosynthetics are being widely used in geoenvironmental, geotechnical and transportation applications. In some of these applications, e.g., waste containment, long-term durability assurance is required. A majority of these geosynthetics are manufactured from polyolefins, such as polyethylene and polypropylene which have a susceptibility to oxidation degradation. Recent research by the principal investigator has provided the first quantitative estimation on the lifetime of some geosynthetics, but the studies have also revealed the complexity of the degradation mechanisms and the limitation of existing acceleration tests. The focus of this research is to design a scientifically-valid accelerated laboratory test to evaluate the oxidation degradation of polyolefin geosynthetics. Oxidation degradation is accelerated by both moderate elevated temperature and oxygen pressure. Therefore, the drawback of the high elevated temperature is compensated by introducing pressure as the second acceleration factor. In addition, dissolution of antioxidants to the adjacent soil medium will be investigated separately. The correlation between soil moisture content and the dissolution rate will be quantified. Five types of geosynthetics will be included in this project.
The acquired experimental data will establish the relationship among the reaction rate, temperature, and pressure. The basic Arrhenius equation will be modified by incorporating the pressure function. This modified Arrhenius equation will be used to predict the lifetime of antioxidants and the overall service lifetime of the geosynthetics based on actual field data on temperature, oxygen content and moisture.
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