Molds & Tooling
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Storage cracking/delayed cracking of high impact polystyrene PS products
Problem Phenomenon
PS products crack hours or days after processing, i.e., delayed cracking, caused by slow release of residual stress.
Cause Analysis
(1) Large residual stress in the product; stress releases over time causing cracking
(2) Uneven product wall thickness, large internal stress at thick walls
(3) Mold temperature too low, fast cooling rate, high residual stress
(4) Improper demolding, mechanical damage becomes crack source
(5) Ambient temperature changes accelerate stress release
Solution
(1) Increase mold temperature, reduce residual stress
(2) Optimize product design, uniform wall thickness
(3) Annealing treatment (60-80°C, 1-4h) to release stress
(4) Ensure uniform demolding force
(5) Store products in a constant temperature environment
Key Takeaway
PS delayed cracking is caused by slow release of residual stress.
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