Production & Quality
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Environmental stress cracking (ESCR) of PP products
Problem Phenomenon
After PP containers are filled with chemicals such as detergents and oils, cracking appears after a period of use, mostly at stress concentration locations.
Cause Analysis
Some PP grades undergo environmental stress cracking in media environments such as surfactants; locations with high internal stress in the product (sharp corners, weld lines, interference-fit assembly areas) crack first under the action of the medium, which is the joint action of material-stress-medium.
Solution
①Select an ESCR-resistant grade when containing chemicals; ②reduce the internal stress of the product by optimizing holding pressure and cooling; ③structurally eliminate sharp corners and avoid excessive assembly interference; ④perform media compatibility/immersion verification before mass production; ⑤switch to a material with better chemical resistance when necessary.
Key Takeaway
Before PP contains chemicals, ESCR verification must be done first: problems occur only when the material grade, internal stress, and medium are superimposed; don't blame only the material for cracked parts—internal stress management and structural fillets are equally important.
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