It is imperative that there are no air bubbles in the hot melt adhesive as this will compromise its ability to adhere properly. However, there should not be any air bubbles in the hot melt adhesive in any state it is in, and the materials used will not automatically generate air bubbles in the adhesive themselves. The next question that arises is, assuming there are bubbles, what causes the bubbles to form in the first place?The existence of air bubbles is evidence that there is gas present within, and there are three different explanations for this.
The first theory is that there is moisture contained within the object, and that the moisture is evaporated at a high temperature before being combined with the glue. Due to the relative viscosity of the glue, it is difficult for the gas to rise to the surface and escape. The second possibility is that, prior to using the hot melt adhesive, other chemical components are mixed together, and eva web adhesive then these latter components react with the hot melt adhesive that is currently being used to release a specific gas. The third possibility is that the quantity of glue in the glue pot is insufficient; as a result, air along with the glue liquid enters the delivery port, and the glue liquid flows out along with the air.
The following strategies can be utilized to rectify the situation in the event that air bubbles have been caused by any of the aforementioned three factors. To begin, investigate the cause of the presence of moisture in the glue by determining whether it is due to the presence of high humidity in the glue pot or to the presence of moisture in the hot melt glue itself. First the glue pot needs to be dried out if it has a significant amount of moisture in it, and then the hot melt glue can be added. Before using the hot melt adhesive, it must first be dried if there is any moisture present on the surface of the adhesive. If there is moisture present in the hot melt adhesive, you should get in touch with the supplier to determine whether or not you will need to replace the hot melt adhesive with another batch or do something else.
For the second possibility, it is recommended that you clean the glue pot before using different brands of hot melt adhesives. This is done to prevent any chemical reactions that may occur between hot melt adhesives that have been prepared from various raw materials. But in general, the same application, the same type of hot melt adhesive, the raw material configuration is not that much different. However, because the amount of hot melt adhesive melted each time is large, a little difference in composition may also cause crosstalk, and after mutual reaction, the performance of the glue will be different from the performance it had when it was first created. If the impact on performance is minimal, it can be ignored; however, if the impact is significant, it is recommended that the glue pot be cleaned and a new pot of glue be re-melted before it is used.
Considering the third possibility, there are some products that do not apply a significant amount of glue, but the pot of glue itself is quite large. At this time, in order to reduce the amount of waste produced, only a few pieces of hot melt glue are placed inside of a glue pot with such a large capacity at each use. Because the glue flows out mixed with air bubbles, the amount of glue applied is actually less, and the amount of glue in the position occupied by the air bubbles is not enough to affect the paste effect. When the hot melt adhesive is completely melted into a liquid, the glue and air will enter the glue delivery port together. Although it may appear that the same volume of glue is applied, this is not the case. Although it may appear that the same volume of glue is applied, the amount of glue applied is actually less.
It's possible that these aren't the only factors that contribute to bubbles forming in hot melt adhesive solutions. When we run into issues, we need to investigate how each link of glue is being eva hot melt adhesive web utilized so that we can get to the bottom of the issue and find a solution.
What causes white hot melt adhesive to change color and become black when it is heated?
What causes white hot melt adhesive to change color and become black when it is heated?.
Why does a good piece of glue at room temperature turn black once it is heated and dissolved? The color of the white hot melt adhesive itself will not change easily before and after heating, but this is not an absolute in actual use.
Because of the variety and quantity of the raw materials that are added during production, the white hot melt adhesive will transform into a different color. What color does the colloid appear to be when it is at room temperature once the finished product has been produced?Because of normal use, its color will not change noticeably even after being heated and dissolved. This is the result of normal use. However, the transition from liquid to solid state of hot melt adhesive can be affected by a variety of different factors.
The pot of glue contains an excessive number of carbides. There will be some remaining glue in the pot of glue after the daily gluing task has been finished, depending on how much glue was used. Particularly, businesses that only use a small amount of glue at the end of each production schedule have a habit of reheating the remaining glue so that it can be used in the following production. After a significant amount of work has been done around the clock with hot melt adhesive eva web adhesive equipment, the majority of equipment operators are unaware that the glue pot needs to be cleaned.
When subjected to cyclic heating, not only will the performance degradation of the hot melt adhesive be exacerbated, but the pot will also produce an increasing number of carbides over the course of the process. The performance of the glue is still being hindered by these carbides, which are also equivalent to impurities. On the other hand, the carbides have not been thoroughly polyester hot-melt adhesive web cleaned up on every occasion, and the total number is appalling. There is no way around the fact that the glue will turn black whenever the sol is combined with a significant quantity of dark impurities.
Raw materials that are of lower quality will undergo mutations when exposed to high temperatures. No matter how well the recipe works, the essential component is the raw material. The functionality of the same raw material can also vary from batch to batch. If the formula is not tweaked, the resulting hot melt adhesive will have a different performance. This is because of the lack of fine tuning. In addition to this, a reaction between the raw materials is going to take place, which calls for extra attention on your part. In order to guarantee the consistency of the recipe, it ought to be examined for an extended period of time at temperatures as high as possible, temperatures as normal as possible, and temperatures as low as possible. The variation in molecular structure that is caused by the reaction between raw materials, in addition to breaking the original characteristics of the raw materials, also has a certain probability of causing a color change. This change in color does not have to be black, and it is also possible for it to change into other colors; this is because the color change primarily depends on the variation condition.
The process of heating, which intensifies molecular motion, increases molecular activity, and increases the frequency of collisions between molecules, is a procedure that poses a threat to the product's stability. The change in color is just one of the manifestations that stems from the fact that heating intensifies molecular motion. When the state of the hot melt adhesive becomes uncontrollable, it is possible to observe a number of peculiar phenomena as the glue melts.