| Contents Notes |
"Flexible membrane liners (geomembranes) used to contain liquid chemicals and leachate at waste containment sites are required to be chemically resistant (compatible) to the liquid. In order to select a liner for use as well as judge its long-term reliability, its chemical resistance against the liquid(s) to be contained must be known. The measurement of compatibility is a complex matter, because a variety of physical and chemical interactions can occur, and compatibility failure of a membrane has never been adequately defined for this application. A search was made for test methods that would ascertain the compatibility performance of liners. Disclosed methods and procedures were examined and compared. Two tests being promoted for general acceptance are NSF Standard No. 54 (a voluntary industry-generated test) and the proposed EPA Test Method 9090. Several other tests developed by liner manufacturers and researchers were found, as well as those methods generally applied to pipes, bottles, film, plastics, rubber sheeting and the like. Although details of tests vary, all are laboratory tests in which selected physical properties of the membrane are compared and evaluated after contact with the liquid for specified periods of time. All are tedious, time-consuming, and potentially costly. Useful data for product specification and application are derived from these tests, but none adequately addresses all issues and questions raised, especially with regard to liner life-time prediction. Nor is any one test universally accepted for use. A combination of compatibility tests (e.g., immersion, stress-crack, and permeation) may be necessary to fully characterize chemical resistance in specific cases. A superior test(s) based on a comprehensive understanding of liner compatibility remains to be developed. Two levels of effort (immediately practical, and long-term) directed at evaluating membrane compatibility are proposed. In the first, a test methodology based on current protocols and methods would be developed to provide three kinds of required information: short-term (testing up to 30 days' exposure), intermediate (testing up to 4 months' exposure), and longterm (greater than 4 months' exposure). In the second, research and test method development would be pursued with the purpose of exploring new methods, techniques, apparatus, etc., for better compatibility characterization." |
