Effect of Stress, Material, and Exposure Route on ESC

Environmental stress cracking (ESC) is a complex cracking mechanism that can manifest in plastics under certain conditions, resulting in components and products failing unexpectedly, and potentially causing customer complaints, property damage, and possible recalls. Although design engineers account for a product’s anticipated end-use environment, the complicated nature of ESC can be difficult to predict. Fractography can assist a root cause investigator or design engineer in determining where and how a crack initiated and progressed through the material to ultimately cause fracture. However, due to the complex nature of ESC, resulting fracture surfaces may present through intricate combinations of characteristic features which stem from variations in the key parameters driving ESC, i.e., stress, the specific nature of the polymer-ESC agent combination, and concentration of ESC agents. This work presents an effort to systematically document the effects of stress level, different polymer-ESC agent combinations, and the nature of exposure to an ESC agent, on resulting fracture surfaces. Industrially relevant polymers, polycarbonate (PC), acrylonitrile butadiene styrene (ABS), and chlorinated polyvinyl chloride (CPVC), will be exposed to different forms of a known ESC agent (as component in a commercial sealant and as a pure reagent) at multiple stress levels, and microscopy of the resulting fracture surfaces will be presented.