Detailed Explanation of Common Problems with Hot Melt Adhesive!

Hot melt adhesive is a plastic adhesive. Its physical state will change with the change of temperature within a certain temperature range. Its chemical properties are non-toxic and odorless, and it is an environmentally friendly chemical.

Hot melt adhesive products are widely used in various fields such as daily life and automobiles due to their excellent characteristics such as easy processing, safe use, environmental protection and speed.

However, for manufacturers of hot melt adhesives, it is inevitable to encounter various production problems. The editor has collected and sorted out the situation.

Hot melt adhesive is not sticky

There are many reasons why hot melt adhesive does not stick. It depends on what factors affect its performance. Temperature is one of the most common reasons at present.

As the weather turns colder, the glue often solidifies when the materials are bonded.

Even if it is not cured, the best bonding effect is missed. Even in some northern regions, the temperature of the material is quite low, resulting in unsatisfactory bonding effect.

Since hot melt adhesive film has certain requirements for the use temperature, the use temperature needs to be adjusted according to the product parameters.

How can we improve the bonding effect? You can preheat the material and use a drying oven or infrared heating to improve the bonding effect.

Wire drawing problem

(1) Curing time of hot melt adhesive

The curing time of hot melt adhesive is crucial to the occurrence of wire drawing. Generally speaking, hot melt adhesive with a short curing time has a low chance of producing wire drawing. This is because the filaments formed when the hot melt adhesive is sprayed out of the muzzle cannot continue to stretch due to the rapid curing, and are prone to breakage. Sometimes, no wires can be seen being pulled out.

(2) Influence of machine temperature

If the temperature is too low, the viscosity of the glue will increase, resulting in stringing.

The temperature is too high and bubbles appear

Hot melt adhesive is generally melted by heating with a hot melt adhesive machine. After the sol, the colloid becomes liquid and can be applied by coating, spraying, or stripping.

During the hot melt glue machine's melting process, bubbles sometimes appear. So what is the reason for the bubbles? Generally, the reason for the bubbles may be that the colloid itself has bubbles, and there are bubbles after melting, or the colloid contains water, which is easy to produce bubbles when heated. In addition, the hot melt glue is destroyed due to the high temperature, decomposes and produces gas, which leads to the generation of bubbles.

Therefore, the operating temperature of hot melt adhesive should be controlled during use, and the equipment should be cleaned regularly to prevent carbon deposition and to avoid local excessive temperature from damaging the colloid and affecting the performance of the hot melt adhesive.

Cold sticking phenomenon

The hot melt adhesive cools down before bonding, which is also called cold bonding. The reasons and solutions for cold bonding are as follows:

(1) The hot melt adhesive is used at a low temperature → increase the temperature;

(2) The open distance is too long → reduce the open distance;

(3) The conveyor speed is too slow → increase the conveyor speed;

(4) The amount of glue applied is insufficient → increase the amount of glue applied;

(5) The temperature of the bonded material and the environment is low → increase the temperature of the environment or the bonded material;

(6) The pressure is not appropriate → adjust the pressure.

In summary, in order to obtain a hot melt adhesive product with performance that meets the requirements, it is necessary to consider factors such as the product formula, processing technology, and actual operation.

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