Bubbles in hot melt adhesive will affect the bonding effect, so there must be no bubbles. However, no matter under any state, there should be no bubbles, and the materials used will not automatically generate bubbles. The problem is, if there are bubbles after the pressure sensitive adhesive melts, where do the bubbles come from, and how can we solve it?
The first possibility: there is water in it. The water is mixed into the glue liquid after high-temperature gasification. Because the glue liquid is thick, it is difficult for the gas to float to the surface and release.
The second possibility: before using hot melt adhesive, there are other chemical components. The latter reacts with the currently used adhesive to release certain gases.
The third possibility: the amount of glue in the glue pot is too small. In addition to the glue liquid, air enters the delivery port together, and the glue liquid and air flow out together.
(1) For the first possibility:
Find out the cause of water in the glue solution. This depends on the humidity of the glue tank or whether the hot melt adhesive itself has water. If the glue can is wet, dry it and put down the glue. If there is water on the surface of the glue, it also needs to be dried before use. If there is water in the glue, it should be handled by the supplier to see if another batch of glue should be replaced.
(2) For the second possibility:
Before using hot melt adhesive of different brands, it is recommended to clean the glue pot first to avoid chemical reaction of glue prepared from different raw materials. However, generally speaking, the raw material configuration of the same type of glue is not very different. However, due to the large amount of glue melted each time, a little difference in composition may also lead to crosstalk. After mutual reaction, the performance of the glue will be different from the original performance. If the performance impact is small, it can be ignored, but if the impact is large, it is recommended to clear the glue pot and melt a pot of glue again.
(3) For the third possibility:
Some products do not need a lot of glue, but the glue pot is very large. At this time, in order not to waste, we put several hot melt adhesive in such a large glue pot every time. When it is completely melted into liquid, the glue and air will enter the glue delivery port together, which seems to be coated with the same amount of glue. However, due to the mixing and outflow of glue and bubbles, the amount of glue applied is actually very small, and the amount of glue occupied by bubbles is insufficient, which affects the pasting effect.
There may be more than these reasons for bubbles in hot melt adhesive. When we encounter problems, we should analyze each link using glue to find out the problems. However, understanding the causes of the above bubbles and their solutions will help to solve the problem of bubbles after pressure sensitive adhesive melts.