Testing for Environmental Stress Cracking (ESC) in Polymers

It has been noted that Environmental Stress Cracking (ESC) has been estimated to be a cause of 15-40% of polymer failures. Thus, when polymers crack, one of the suspect causes is ESC. These polymers include polycarbonate (PC), polyvinyl chloride (PVC), chlorinated PVC (CPVC), low density polyethylene (LDPE), high density polyethylene (HDPE), polysulfone (PSF), polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(2,6-dimethyl-1,4- phenylene oxide) (PPO), Styrene acrylonitrile resin (SAN), Nylon 6, and Nylon 6,6 as well as blends. In order to verify that a suspect agent could have caused the cracking, certain standard tests may be performed such as ASTM D543, D1693, D3929, D5419, F484, and F791. Sometimes, due to the the product shape and size, these must be modified to suit a specific application. This works well if there is a suspect agent, but attempting to verify the presence of an unknown agent post-failure requires non-standardized tests. These non-standardized tests include solvent extraction followed by micro-FTIR analysis, small sample passive emission testing in a vial with a solid phase microextraction (SPME) fiber during controlled heating, small sample emission testing in a controlled chamber during controlled heating using ASTM method D7706 with US EPA TO-17 and ISO 16000-6 by GC-MS for the analysis. As always, controls and background confounding factors need to be assessed.