Preventing Char in Hot Melt Adhesives

May 15, 2019

If you work with hot melt adhesives you probably, unfortunately, have experienced char more than a few times. And if you have, you know that preventing char is vital to keeping you from bringing a halt to production.

Char is adhesive that has been burned as a result of contaminants or over exposure to heat. Some ways that char can occur are:

– Contaminants such as dust or paper getting into the adhesive
– Exposing the adhesive to high temperatures for an extended period of time
– Exposing small amounts of the adhesive to heat and oxygen
– Not properly cleaning or maintaining hot melt equipment, causing external particles to get inside and burn
– Hot spots in the hoses
– Dead spots in the applicator heads

The results of char in your hot melt operations can be disastrous. Filters and nozzles become clogged. Pumps break. And once char is living in your hoses, it is nearly impossible to get it out. You will be forced to constantly shut down your line to address issues with the equipment, all thanks to char.

How to Prevent Charring

But fear not! There are ways you can be proactive in order to prevent char in your hot melt operations and keep your production line running smoothly. Here are a few tips we recommend:

1. Operate Your Equipment at the Right Temperature

All manufacturers of adhesives have a recommended application temperature.  Exposing the hot melt to temperatures above that recommendation will cause char to form significantly faster. Be sure you’re using the correct temperature at all times.

2. Use a Proper Adhesive Level

Keeping the glue as close to full as possible is best practice. As the adhesive level goes down, a small amount of hot melt residue is left on the wall of the tank.  The heat from the wall and the oxygen around it drastically increases how quickly char can form. By keeping the tank full, you are minimizing the opportunity for char to develop in that area and you keep the viscosity of the adhesive as consistent as possible. To optimize your tank system, you can add an auto-feed system or switch to the InvisiPac, a tank-free system.

3. Use the Right Size Tank

Make sure you size your melt tanks properly. Using a tank that is too large will cause your adhesive to sit for long periods of time without turning over and this will eventually cause it to burn. Plus, if the system itself is sitting idle, the hot melt system should be put into setback mode. This will help minimize the possibility of over-cooking the adhesive.

To avoid this situation altogether, you can use the InvisiPac hot melt system. It has no tank and rapidly melts the glue as needed. It also does not need a setback mode because it will turn off if idle for a period of time and then fully heat back up in as fast as 10 minutes. If you want to learn more about InvisiPac, call us today!

4. Take Proper Care of Your Heated Hoses

Don’t overlook your hoses! When heated hoses have adhesive in them for too long with no movement, a film of adhesive may form on the inside and will eventually break down and char. Once that happens, the char is at risk of being knocked loose and clogging filters and nozzles. You should also avoid leaving hoses on the floor and pinching them with zip ties or other straps. The cold floor will create a cold area in the hose, changing the flow inside and causing glue to stay longer in that area – causing char.

5. Choose the Correct Technology

In most applications there is more than one type of adhesive that will work, but not all hot melts resist char as well as others. Make sure you choose a technology that will give you the longest pot life possible in order to greatly reduce your chance of building char.

6. Be Proactive with Preventative Maintenance

Preventative maintenance cannot stop char from developing, but it will greatly reduce your chances of char affecting your production time. By properly cleaning out the tank and replacing filters in a timely manner, you reduce the chances that char will make it to your nozzles and cause downtime. And when you keep your adhesive and tank clean, it also reduces the chance of harming the pump.

Char happens. If you’d like Chicago Glue to help you with preventing char by repairing your machines or conducting preventative maintenance, contact us today. While we work on your equipment, we can rent you back up machinery to help you avoid shutting down your line and causing a glue-mergency!