南京維嘉標(biāo)簽印刷有限公司
Nanjing Weijia Label Printing Co., Ltd
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Does the label bulge? Rise and fall? Perhaps these reasons caused the trouble!
Labeling and bulging
Bulging during labeling is also one of the common problems in self-adhesive label labeling. This problem often occurs in batches and is only discovered after a period of time after labeling, and sometimes even discovered by the end user during pre shipment inspection, causing great trouble and losses to the end user. The main reasons for label bulging are as follows:
1. Label absorbs water and expands
Labels may lose a certain amount of moisture during processing. If the moisture in the environment suddenly increases during use, it can cause the labels to absorb water and expand after labeling, especially for paper surface materials. Due to the label being attached to the object, the expanded area will form bubbles or bulges.
When encountering such problems, it is generally recommended to polish or cover the label surface of paper surface materials with film to isolate air and moisture. If due to special reasons, it is not possible to polish or film the label, it is best to open the packaging and leave it for 24 hours to fully balance the moisture in the air before labeling. At the same time, if the object being pasted is an object that is easily affected by humidity, such as corrugated cardboard boxes, it also needs to be treated in the same way.
2. Chemical reaction occurs between the adhesive and the surface of the substrate
Many stickers are usually plastic products, and various additives are added during the processing. Some plastic products made from recycled plastic have more complex components. The glue in adhesive materials is a chemical product that sometimes reacts with some components in plastic products. This reaction produces some gas, which cannot be released due to the label being attached to the surface of the object, forming bubbles or bulging. In this case, if the label is opened, it will be found that there has been a significant change in the adhesive layer, such as a phenomenon similar to dissolution in the adhesive layer.
When encountering this problem, it is recommended to replace it with another type of adhesive material to process the label, and it is necessary to conduct labeling testing before processing to confirm that there will be no chemical reaction between the two before proceeding with production.
Label lifting
Labeling warping is a serious labeling problem, generally divided into two situations: one is the warping that occurs a few hours after labeling, and the other is the warping that occurs a few days after labeling. The main reasons for label warping are as follows:
1. Insufficient adhesive strength of the adhesive
It is easy to understand that the stickiness of the adhesive is insufficient, resulting in label warping. Here, it should be noted that the adhesive of self-adhesive materials usually has two viscosity indicators: one is the initial viscosity, and the other is the holding force. Among them, initial viscosity refers to the viscosity exhibited by the adhesive when it is first applied to the object being applied, which is also commonly considered as a viscosity index. Simply put, the simplest way to feel the strength of a glue's viscosity is to remove the label and feel the glue's viscosity with your hand. This viscosity is the initial viscosity of the glue. If the initial viscosity of the adhesive is not enough, it will cause warping within a few hours after labeling.
If the label shows warping a few days after being applied, it indicates that the adhesive has insufficient adhesion. We know that a self-adhesive label is a flat surface, and many objects being attached are curved surfaces. When a flat label is attached to a curved object, the surface material of the self-adhesive label will have a reverse force to break free from the surface, which requires the adhesive's holding force to play a role. Holding force, also known as shear viscosity, is the aggregation force between adhesives. If the adhesive holding force is not sufficient, the continuous reverse force on the label surface will cause delamination and detachment between the adhesives, leading to label warping.
Once the label is warped, how can we determine whether it is due to insufficient initial adhesive force or insufficient holding force of the adhesive? In fact, the method is very simple. If the initial adhesion of the adhesive is not enough, the label will curl up a few hours after labeling, and the longest time will not exceed 24 hours. Moreover, the adhesive will rarely remain on the surface of the object being pasted; If the adhesive holding force is insufficient, the label will generally start to warp 24 hours after labeling, and careful observation will reveal that due to the delamination of the adhesive, some of the adhesive will remain on the surface of the object being pasted.
2. There is silicon additive on the surface of the pasted object
Some patches will be cleaned with a liquid containing silicon additives, such as blood collection tubes. The purpose of doing this is to prevent the collected blood from hanging on the wall of the test tube, but the silicon additive also has a release effect on the adhesive, making it difficult for the label to stick on the surface of the adhesive.
When encountering such problems, the judgment is also very simple. You can take several test tubes that have not been cleaned with silicon additives and test tubes that have been cleaned with silicon additives for labeling testing. If the test tubes that have not been used with silicon additives do not find any label warping, then the reason is obvious. To solve this problem, it is necessary to communicate with the end user and control the usage of silicon additives within a reasonable range, otherwise it will lead to label warping in the later stage.
3. Improper selection of labels (frozen labels)
At present, the minimum labeling temperature for most self-adhesive materials is between 8 ℃ and 10 ℃, which is the temperature range within which the adhesive can function properly. However, some customers in the refrigeration industry need to label in low-temperature environments, and using this conventional adhesive material can easily cause the label to warp.
There are two ways to solve this situation: one is to use special adhesive materials suitable for labeling in low temperature environments, which are usually expensive and directly increase the cost for end users; The second is to first attach the label to the surface of the object under normal temperature, and then pack the product in a low-temperature environment after being left for 24 hours.
