How to make plastics resistant to environmental stress cracking?

Here's a breakdown of the failures that happen during ESC:

1. Brittle fracture: Unlike many plastics that exhibit some ductility (stretching) before breaking, ESC failures occur through brittle fracture. This means the plastic cracks in a sudden and rapid manner, often with minimal deformation.
2. Stress levels: Interestingly, the stress required for ESC failure is often below the yield point of the plastic itself. This means the plastic wouldn't normally break under that level of stress in a non-corrosive environment. The presence of the environmental agent weakens the intermolecular forces holding the polymer chains together, making the plastic more susceptible to cracking even at lower stress levels.
3. Slow crack growth: ESC is not a single, instantaneous event. It typically involves a slow propagation of cracks over time. The environmental agent can initiate microscopic cracks in the plastic, and these cracks gradually grow with continued stress and exposure.
4. Multiple cracks: Unlike a single point of failure, ESC can often lead to the formation of multiple cracks along the stressed area of the plastic. This can be because the environmental agent can attack various locations along the stressed zone, creating multiple weak points.
5. Surface and internal cracks: Cracks caused by ESC can initiate on the surface of the plastic, where it's directly exposed to the environmental agent. However, cracks can also propagate internally, starting from microscopic flaws within the material.