ESC Fractography: A Study Varying Stress in Two Amorphous Polymers

Environmental stress cracking (ESC) is one of the most common, but also complex cracking mechanisms that can manifest in plastic components and products. This cracking mechanism can occur in certain polymers when they are exposed to both moderate tensile stress and an incompatible chemical (ESC agent) over extended timeframes. Designers and manufacturers are often blindsided when their plastic component and products suddenly fail, potentially resulting in customer complaints, property damage, and possible recalls. 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, one of these primary ESC parameters, on resulting fracture surfaces. Industrially relevant polymers, polycarbonate and chlorinated polyvinyl chloride (CPVC), will be exposed to known ESC agents at multiple stress levels, and microscopy of the resulting fracture surfaces will be presented.