An alternative approach to the evaluation of the slow crack growth resistance of polyethylene resins used for water pipe extrusion

Abstract

High-density polyethylene (HDPE) pipes have been largely employed in water and gas distribution systems. In spite of offering significative advantages over other materials, HDPE pipes suffer from premature failures due to creep fracture. The current industrial criterium for design and sizing of HDPE pipes is discussed. The concept of ‘regression curve,’ i.e. of a time-to-failure criterium based in long-term-hydrostatic strength (LTHS) tests, is criticised and concluded to be unsatisfactory for this purpose. An alternative approach is suggested, which is based on shorter-term tests. This is illustrated by testing five HDPE resins designed for pipe extrusion and comparing with their standard ‘regression curves’. The obtained results are consistent with the ‘regression curve’-based analysis, justifying the use of the alternative approach in the industry.