Why does the hot melt adhesive turn black when heated?
The color of the hot melt adhesive itself will not change easily before and after heating, but it is not absolute in actual use, so why does a good piece of glue at room temperature turn black once it is heated and dissolved?
At the production level, the hot melt adhesive will change in color due to the type and weight of the raw materials added. Once the finished product is produced, what color is the colloid at room temperature, and after heating and dissolving, its color will not change significantly, which is the result of normal use. But in fact, there are many factors that will affect the state change of hot melt adhesive.
1. Too much carbide in the glue pot
After the daily gluing task is completed, there will be more or less glue residue in the glue pot. In particular, companies that use a small amount of glue after each production schedule habitually reheat the remaining glue for use in the next production. After many hot melt adhesive equipments work every day, most equipment operators do not have the awareness of cleaning the glue pot. Under cyclic heating, not only will the performance of the hot melt adhesive deteriorate, but also more and more carbides will be produced in the pot. These carbides are also equivalent to impurities, which continue to hinder the performance of the glue. And the carbide has not been cleaned up, and the amount is very scary. Every time the sol is mixed with a lot of black impurities, there is no way for the glue to stay black.
2. Poor quality raw materials mutate at high temperature
No matter how good the recipe is, the ingredients are the foundation! The same raw material has different properties. If the formula is not fine-tuned, the properties of the produced hot melt adhesive will be different. In addition, there will be reactions between the raw materials, which should be paid special attention to. The test should be carried out at high temperature, normal temperature and low temperature for as long as possible to ensure the stability of the formula. In addition to breaking the original characteristics of the raw materials, the molecular structure variation generated by the reaction between the raw materials also has a certain probability of changing the color, but it may not turn black, and it is also possible to turn into other colors, which mainly depends on its variation. Condition.
Color change is just one of the manifestations, which arises from the fact that heating intensifies molecular motion, increasing molecular activity and the frequency of intermolecular collisions, a process that challenges product stability. Therefore, when purchasing hot melt adhesives, you must choose a reliable hot melt adhesive manufacturer.
