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Improved stress-cracking resistance in high-density polyethylene (HDPE) geomembranes has been a quest of our industry and a hot research topic for years. The Geosynthetic Institute (GSI) has been working in this area since the mid-1980s. The GRI GM13 standard specification for HDPE geomembranes has moved the ASTM D5397 (appendix) single point notch constant tension load result requirement from 200 to 300 and finally to 500 hours over the last 30 years. It is interesting to note that some HDPE geomembrane formulations have a considerably higher value.
Igepal CO-630 is referenced in ASTM and the European Committee for Standardization (CEN) norms-test methods as the reagent for the stress-cracking test. Igepal CO-630’s official International Union of Pure and Applied Chemistry (IUPAC) name is octylphenoxypolyethoxyethanol. Unfortunately, it has now been listed as a priority pollutant by some countries and is no longer available for laboratory use in several areas, most notably in the European Union (EU) and Canada. This development has manifested itself over the past several years. Obviously, our industry is searching for an equivalent and is now in need of available alternatives that can be used globally.
The EU no longer allows the sale of Igepal CO-630 to people in production industries (i.e., large quantities) due to eco-issues and health. This is apparently an EU Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) directive, not a law. As such, GSI has been tasked with finding a replacement for the surfactant used in several stress-cracking tests. We know that there are hundreds of commercially available nonionic surfactants in the family of octylphenoxypolyethoxyethanol. Unfortunately, all have unique characteristics that will affect stress cracking in HDPE differently.
The purpose of this article is to not only make you aware of the situation, but also to solicit help in finding an alternative. GSI is now taking a proactive approach to finding substitutes to Igepal CO-630. We realize that these substitutes may have intensity, observable differences and perhaps even different handling characteristics. GSI is doing preliminary work with candidate surfactants. Please note: In addition to changing the surfactant, we would also like to increase the bath temperature from 122˚F to 149˚F (50˚C to 65˚C) so that we can shorten the test time.
After confirmation of an alternative group of surfactants, we want to initiate a round-robin test program with several geomembranes (each having different formulations). If you would like to participate in this round-robin, please contact us at gsigeokoerner@gmail.com. We would greatly appreciate hearing from you.