Sheet & material defect
Crazing & stress cracking in thermoforming
Also called: Stress cracks, ESC
Crazing is a network of fine surface cracks; environmental stress cracking (ESC) is cracking triggered when a stressed part meets certain chemicals. Both stem from locked-in stress meeting a trigger.
Why it happens
- High residual/moulded-in stress from forming
- Contact with incompatible cleaners, oils or solvents
- Sharp corners concentrating stress
- Wrong grade for a chemical-contact application
How to fix & prevent it
- Reduce residual stress with even heating and cooling
- Select a chemical-resistant grade (e.g. ESCR HIPS, HDPE, PP)
- Increase radii to lower stress concentration
- Anneal or validate against the service chemicals
How Indu prevents it: For chemical or cold-storage duty we specify ESCR and chemical-resistant grades and form them with low locked-in stress, then validate against the real service environment.
Troubleshooting help
Fighting crazing & stress cracking on a part?
Send your drawing, sample or a photo of the issue — our engineers will diagnose the cause and reply with the tooling, material and process fix, usually within 24 hours.
ISO 9001:2015 certified · Most quotes back within 24 hours