Why do zipper bags have wrinkles?

January 5, 2023

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The zipper bag has the advantages of easy access and repeated use, so it stands out in the domestic and foreign markets, and the market scale continues to expand. But we found that zipper bags are more prone to wrinkles, why?There are two common folds in zipper bags: one is partial delamination or partial folds at both ends of the zipper; the other is folds at the seal between the zipper and the bag body.In general, the wrinkles at both ends of the zipper bag are related to the melting point of the zipper itself. When the zipper plastic bag is heat-sealed, the zipper and the plastic film are heat-sealed in the same environment, so it is necessary to pay attention to the melting point and shrinkage rate of the zipper, which should be lower than or equal to the melting point of the composite film and the shrinkage rate of the heat-sealing layer of the composite film. In this way, the probability of wrinkles in the zipper bag can be reduced.In addition, the cooling conditions in the bag making are also one of the reasons for the wrinkles of the zipper bag. If the composite film and zipper of the zipper bag that has been bagged are still in a viscoelastic state, heat shrinkage is likely to occur during storage, resulting in wrinkles in the zipper bag. On the contrary, if the zipper can be sufficiently cooled before the bag making process is completed, the probability of wrinkling under normal storage conditions will be greatly reduced. Therefore, before the bag making is completed, the temperature of the cooling surface of the bag making machine must be strictly controlled to reduce the probability of wrinkles in the zipper bag.

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