HDPE Geomembrane Stress Cracking: From There to Here to Where?

Stress cracking (SC) in high density polyethylene (HDPE) has been a problem, an interesting research topic, and an agent for improved geomembrane performance. The Geosynthetic Research Institute and Professor Robert Koerner have been front and center in this effort over the years since about 1984. In this paper we take a look back and a look forward at this still developing story. The internationally accepted GRI.GM13 standard for HDPE geomembranes specified SCR (SC resistance) from 200 hr to 300 hr, recently increased to 500 hr in the ASTM D5397 standard test procedure. And some geomembranes have SCRs exceeding 2000 hr. However, we have not seen an end to SC yet, and we may even see in increase in SC events as older HDPE geomembranes reach the ends of their natural service lives, oxidize, and crack. But there are excellent new high performance, premium, high temperature, and hot liquid rated HDPEs, some using quite different resins, to take their place. And as SCRs increase conformance testing times increase which engenders further research into accelerated methods to generate stress cracking resistances rapidly. One of these methods is to assess SCR from the post-yield strain-hardening segment of a uniaxial tensile stress/strain curve; a test that can be done very quickly.