Environmental Stress Cracking (ESC) is an accelerated failure of a plastic material due to the combined action of environmental exposure and stress. Stresses may be residual, assembly- or application-induced.

ESC has been attributed to the root cause of 15% of all failures of plastic components in service. That’s why understanding the potential impact of ESC upon your plastic product is important, especially for critical applications such as medical devices.

ESC arises from the combination of:

• Exposure to chemicals either that swell or wet the plastic, or those that chemically react with the plastic. Numerous studies link the ability of a chemical to swell a plastic with its ability to craze the plastic;
• Amorphous plastic material tends to be more prone to failure;
• Tensile stress present in the plastic.

To reduce the failure from ESC plastic product manufacturers should consider:

• Material selection. Standard test such as ASTM D1693 offer a way to test the susceptibility of a particular plastic to certain environmental exposure;
• Stress from component processing. Polarising film allows the visualisation of stress within the plastic component;
• The service use of the plastic component. Is stress induced during application or is there exposure to specific active chemicals. In the latter case the presence of trace quantities of an active chemical in a bulk material may be the originating cause.