Temperature Lowering
How Lowering the Temperature Helps Reducing Adhesive Charring
Adhesive charring is a nuisance. Burnt hot melt impairs adhesive application and can destroy entire systems. As annoying as it is, it’s just as common. The good news is:
There is something one can do about it! Since the main reason for charring is overheating, lowering the adhesive temperature during production stops is a good approach.
At the end of the day, this saves a lot of time – in the form of further production stops – and money, because less waste is produced.
Melted Adhesive Does Not Like to Stand Still
The adhesive application system is usually switched on and off with the overall machine, so that it is ready to glue when the production starts. But when the line comes to a standstill – for example because of retooling – the adhesive application system stands still, too.
Of course, operators who aim at a seamless production may prefer to leave the adhesive at processing temperature when it is not used for some time, especially if they do not know
exactly how long the interruption will last.
But there is a problem: If melted adhesive stands still because is not used for a longer period of time, it starts to decompose. The first signs of decomposition are stringing and discoloration of the adhesive. The adhesive becomes more viscous, the adhesive pressure decreases, and ultimately, the adhesion suffers.
If, in addition, the adhesive filters are clogged, all alarm bells should ring: The adhesive
is about to burn! This process is known as adhesive charring, cracking or carbonization of the adhesive.
Charring Causes Production Downtimes
It’s no secret: Burnt adhesive loses its bonding quality and the product will be waste! Charring also clogs the application heads and hoses.
As a result, production comes to a standstill – this time because of the adhesive application system! Minor adhesive charring can be removed by flushing the system, but it is not always possible to rinse everything out.
In the worst case, irreparable damage is caused to the components. An enormous loss of quality and time. What can be done to prevent this? The adhesive can be protected by lowering its temperature when the gluing system is not being used but should not be switched off completely.
When Does It Make Sense to Lower the Temperature?
If the adhesive application system is not needed for more than 30-45 minutes, it is recommended to lower the temperature of the adhesive by at least 20-30°C of the current processing temperature.
This protects the adhesive, but it is also back to operating temperature in just a few minutes at any time. These few minutes are worth gold. It is only a fraction of what it costs in time and money to clean or even replace a complete adhesive application system due to charred adhesive!
The advantages are at hand: improved quality, increased process reliability and longer machine uptime. Overnight or for longer interruptions, the adhesive application system can
of course be switched off completely.
*For the past 12 years, he has overseen the service hotline, supporting customers from a wide range of industries with technical problems.
Robert Seiferth*
Technical Account Manager
Robatech Germany
