What are the reasons for carbonization of hot melt adhesive?

The three main reasons for carbonization – overheating, pollution, and oxidation – occur regularly in most EVA hot melt adhesive packaging applications. Gain a detailed understanding of these reasons and how to avoid them.

Overheating

The formation of carbon starts from the decomposition of hot melt adhesive and forms gel after being heated for a long time. These gel cannot flow through the hot melt system and eventually stick to the wall of the bath and hose. Once adhered to the system components, gel will be exposed to overheating environment for a long time and will be burnt or “burnt”.

Most hot melt systems use melting tanks to heat hot melt adhesive to the desired temperature. The hot melt adhesive along the outside of the water tank is exposed to higher heat and burns faster, just like a clay pot can produce burnt food around it. This inefficient heating method is often made more complex by some common practices in many terminal packaging applications:

1.  Keep the hot melt adhesive system and measuring tank open for a long time

2.  Add system heating settings to compensate for temperature loss or “shock” when adding room temperature to the heating system

3.  Using disproportionate bath sizes throughout the entire adhesive

Regardless of the application, if the hot melt adhesive is left in the heating tank for a long time, it will degrade and produce adhesive charcoal.

Pollution

Although heat and oxidation are the two main reasons for the carbonization of hot melt adhesives, environmental pollutants such as dirt and dust can also cause carbonization. Many manufacturing facilities, such as bakeries, dairy production, and paper processing; –  Due to the processes involved, a large amount of pollutants float in the air. If the ventilation is poor and the operator opens the lid on the hot melt system, particles will enter the melted hot melt adhesive and burn, turning into hot melt adhesive and carbonizing, sticking to system components.

Prevention is the best method for dealing with carbonization of hot melt adhesive during terminal packaging operations. By using appropriate equipment and procedures, you can prevent hot melt glue carbonization from causing costly downtime due to unplanned maintenance issues.

Oxidation

If the molten hot melt adhesive is regularly exposed to air, it will also form carbonization of the hot melt adhesive. If the liquid level control of hot melt adhesive is not properly maintained, or if the operator keeps opening and closing the lids on the system, this situation may occur. This is a common situation as most hot melt adhesive systems require manual feeding of EVA hot melt adhesive particles, as automatic feeding systems do not exist or cannot be used.