Frequently asked questions about hot melt adhesives
Published on Nov. 09, 2019
Hot melt adhesive is a plastic adhesive. Its physical state changes with temperature within a certain temperature range, and its chemical properties are non-toxic and tasteless. It is an environmentally friendly chemical.
First, the glue is not sticky
There are many reasons why hot melt adhesives are not sticky, and temperature is one of the most common causes. As the weather turns cold, the glue tends to solidify when the material is bonded. Even if it is not cured, it misses the best adhesion. Even in some northern regions, the temperature of the material is quite low, resulting in an unsatisfactory adhesion. Since the hot melt adhesive film has certain requirements on the use temperature, it is necessary to adjust the use temperature according to the product parameters. The material can be preheated and heated by a tunnel or infrared to enhance adhesion.
High Grade Hot Melt Glue Stick
Second, there is a problem of drawing
(1) Curing time of hot melt adhesive. The curing time of the hot melt adhesive is very important for the drawing phenomenon. Generally, the hot melt adhesive with a short curing time has a low probability of drawing, because the filament formed during the hot melt adhesive is sprayed out of the muzzle due to the rapid speed. Curing, can not continue to stretch, prone to breakage, and sometimes can not see the wire pulled out.
(2) The influence of the temperature of the machine. The temperature is too low, so that the consistency of the glue itself is increased, and the drawing phenomenon occurs.
Third, the temperature is too high
The hot melt packing adhesive is generally melted by a hot melt glue machine, and the state of the colloid after the sol becomes a liquid, which can be applied by coating, spraying, and slicing. In the process of melting the melter, sometimes bubbles appear, so what is the cause of foaming? The reason for foaming may be that the gel itself has bubbles, bubbles after melting, or the gel contains moisture, heated At the same time, it is easy to generate bubbles, and the hot melt adhesive causes damage to the colloid due to high temperature, and decomposes to generate gas, which leads to the generation of bubbles. Therefore, the hot melt adhesive should be controlled in the use process, and the equipment should be cleaned regularly to prevent carbon deposition, to avoid damage to the colloid caused by excessive local temperature, and to affect the performance of the hot melt adhesive.
Fourth, cold sticky phenomenon
The bookbinding hot melt adhesive is cooled before bonding, also known as cold sticking phenomenon. The causes and solutions for the cold sticking phenomenon are as follows: (1) the hot melt adhesive is used at a low temperature → the use temperature is increased; (2) the open distance is too long → decrease Open distance; (3) conveyor belt speed is too slow → increase conveyor speed; (4) insufficient glue application → increase glue application; (5) low viscosity of the material and ambient temperature → increase the temperature of the environment or the material to be bonded; ) The pressure is not suitable → adjust the pressure. The hot melt adhesive has a cold sticking phenomenon, and it is necessary to analyze one by one for different reasons and obtain a corresponding solution.