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What should I do if the opening of the packaging bag is rolled inward, outward, or in an S-shape?
Release time:2019-10-28
Packaging bags are made of various plastic films. Differences in film properties and production experience lead to inconsistent packaging bag quality. Today, Shunxingyuan Packaging, a professional flexible packaging manufacturer, will combine the abnormal phenomena that often occur during bag making to interpret how experienced packaging bag manufacturers safeguard the quality of packaging bags.
Packaging bags are made of various plastic films. Due to differences in film properties and production experience, the quality of packaging bags varies. Today, Shunxingyuan Packaging, a professional flexible packaging manufacturer, will combine the abnormal phenomena that often occur during bag making to interpret how experienced packaging bag manufacturers safeguard the quality of packaging bags.
1. Inward curling of the bag mouth
The heat-sealing layer material has low heat resistance and excessive shrinkage, resulting in inward curling;
Inconsistent tension between the two substrates. If the inner layer tension is greater than the outer layer tension, the finished bag opening will curl inward;
The heat resistance of the heat-sealing material is lower than the bag-making heat-sealing temperature;
The base film has a smaller heat shrinkage rate than the inner layer film, resulting in inward curling after heat sealing.
2. Outward curling of the bag mouth
The outer layer material has a greater heat shrinkage rate than the inner layer material;
Excessive residual solvent in the film; especially with more OH groups, it is easy to absorb moisture, and bubbles are generated at the heat-sealing position at this time;
Excessive adhesive coating amount, not completely dry, excessive residual solvent, and tunnel phenomenon at the heat-sealing position;
The heat resistance of the outer layer material is lower than the heat-sealing material, resulting in outward curling;
Residual stress remains after the material is cured and shaped, especially when the composite film is thinner, the base material tension is too large, while the composite material tension is too small, and the finished bag is more likely to curl outward.
3. S-shaped curling
The BOPA film absorbs too much moisture, resulting in S-shaped curling after bag-making heat sealing;
The ratio of longitudinal and transverse heat shrinkage of the BOPA film is too large, generally it should be controlled to a difference of 0.5;
The heat shrinkage rate of the BOPA film is too large, causing curling, and the longitudinal and transverse shrinkage rates exceed 3.0%. (Ordinary composite packaging)
In summary, the curling of the packaging bag mouth is a problem that already exists before bag making. Shunxingyuan Packaging analyzes the reasons and adjusts the corresponding process parameters according to the different curling directions and shapes, which can solve these problems.
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