Extrusion & Post
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Annealing Treatment of Biaxially Oriented Polypropylene Film Products to Improve Stress
Problem Phenomenon
The internal stress of the product is large after processing; annealing treatment is used to reduce residual stress and improve dimensional stability and stress cracking resistance.
Cause Analysis
(1) The residual stress generated during processing needs to be released by annealing
(2) The service environment temperature of the product is high, and non-annealed products are prone to deformation or cracking
(3) High-precision products need annealing to stabilize dimensions
(4) The product has a large wall thickness and large residual stress, requiring annealing
(5) The product needs to contact chemical media, and annealing improves stress cracking resistance
Solution
(1) The annealing temperature is set at 5-10°C below the heat deflection temperature (usually 60-80°C)
(2) The annealing time is determined according to the wall thickness of the product, usually 1-4h
(3) The annealing environment temperature is uniform, and the temperature difference does not exceed ±3°C
(4) Cool slowly to room temperature after annealing
(5) After annealing, check the dimensional change of the product and the stress improvement effect
Key Takeaway
Annealing treatment is an effective method to reduce the residual stress of products.
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