Service Life of HDPE Drain Pipe: The Recently Proposed Specification and an Alternative Approach

The major factors affecting the short term and long-term performance of plastics in engineering applications include a) chemical makeup, molecular architecture, and additives; b) raw material and component manufacturing processing parameters, and c) installation and service conditions that include load, loading rate, temperature and other environmental conditions. The successful design of plastic components for an intended application requires an understanding of the role of the above factors together with economic considerations that account for the cost of fabrication as well as for the cost of failure. Material characterization and ranking with respect to strength, toughness and durability provide a basis for rational design with plastics. There are industrial standards and regulations developed to assist in product qualification. Advantages and limitations of existing standards and methods for lifetime prediction of engineering thermoplastics, as well as the recently proposed specification for predicting a 100-year service life of high density polyethylene (HDPE) drain pipe will be discussed. Extrapolation of relatively short-term (1 – 1.5 years) test data into a 100-year service life is a challenging task. Purely empirical correlations leave the currently proposed extrapolation highly uncertain. A detailed understanding of the potential failure mechanisms and knowledge of fundamental physics of accelerating test conditions are necessary to build confidence in such an extrapolation technique.