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Reasons and Solutions for Curling and Warping Edges of Packaging Bags
Release time:2019-12-14
Curling and warping can sometimes occur in packaging bags due to various reasons and require different solutions. Below, Shunxingyuan Packaging, a professional flexible packaging manufacturer, shares its production experience to explain the causes and solutions for curling and warping in packaging bags, helping you order higher-quality packaging bag products.
Packaging bag Sometimes curling and warping occur in different situations These situations have different reasons, and also have different different solutions. Below, Shunxingyuan Packaging, a professional flexible packaging manufacturer, will interpret the reasons and solutions for curling and warping of packaging bags based on its own production experience, helping you order better quality packaging bag products.
I. Curling and warping
1. Bag mouth inward curling
Reason:
Heat-sealing layer material heat (wet heat) resistance is low ， Shrinkage rate is too large ， Inward curl;
The tension of the two substrates is inconsistent, and the inner layer tension is greater than the outer layer tension ， Then the finished bag opening curls inward;
The heat-sealing temperature of the material is lower than the bag-making temperature;
The shrinkage ratio of the base film is smaller than that of the inner layer film ， Inward curl occurs after bag making;
PA film moisture absorption ， Inward curl occurs after material elongation.
Solution:
Check the reason and then solve it accordingly.
2. Outward curl
Reason:
The shrinkage rate of the outer layer material is greater than that of the inner layer material;
More residual solvent in the film; especially containing More OH radicals are easy to absorb moisture;
Excessive amount of adhesive coating, not completely dry, more residual solvent ;
The heat resistance of the outer layer material (wet heat) temperature is lower than the heat-sealing material, resulting in outward curl;
Residual stress remains after material curing and shaping Especially when the composite film is thinner, the substrate tension is too large, while the composite material tension is too small, the finished bag is more likely to curl outward.
Solution:
Check the reason and then solve it accordingly.
3. S-shaped curl
Reason:
BOPA film absorbs too much moisture, causing curling;
The difference between the longitudinal and transverse shrinkage of BOPA film is too large;
The wet heat shrinkage rate of BOPA film is too large, causing curling.
Solution:
BOPA film moisture absorption rate ≤5%;
The difference between the longitudinal and transverse shrinkage of BOPA film ≤0.5%;
When making boiled and steamed bags, The wet heat shrinkage rate of BOPA film is measured under the condition of 120℃ for 40min 。
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