How to Prevent Adhesive Charring: Causes, Prevention, & Solutions

Q: What causes hot melt char in hoses?

Adhesive char in hot melt hoses is typically caused by excessive heat, prolonged dwell time, oxidation from air exposure, and contamination from degraded material that can form carbonized particles and clog the system.

Q: Can you clean a hot melt hose, or does it need to be replaced?

In some cases, hoses can be cleaned using specialized flushing compounds designed to remove degraded adhesive, but their effectiveness may be limited depending on the severity of the hot melt adhesive buildup. If the glue buildup is severe or has hardened inside the hose, replacing the hot melt hose is often the more reliable and cost-effective solution.

Q: How often should you maintain or flush a hot melt system?

Maintenance frequency depends on usage and adhesive type, but most systems benefit from routine inspection and periodic flushing to prevent char formation and extend equipment life. For high-use operations, monthly or quarterly cleaning is common. On the other hand, lower-use systems may require less frequent maintenance. We offer a regular hot melt equipment maintenance program to help.

Table of Contents

What is Adhesive Charring?
Common Causes of Adhesive Charring
Signs of Adhesive Charring
How to Prevent Hot Melt Adhesive Char
FAQs

The last thing any business wants is to halt production because of an issue with their machines. Unfortunately, unexpected downtime is an all-too-common occurrence, and adhesive charring may be to blame.

What is Adhesive Charring?

Adhesive charring refers to heated or burnt hot melt glue that has broken down and formed carbonized particles that create a gel or solid. Adhesive char is typically the result of prolonged exposure to heat or oxidation and leads to the degradation of the adhesive.

Over time, this burnt, often black glue can build up and cause major problems, including:

Clogged hoses and applicators
Uneven adhesive application
Defective products or packaging
Downtime in production for cleaning, parts replacement, or equipment repair

Altogether, these issues can cost businesses a lot of wasted time and money.

Common Causes of Adhesive Charring

Adhesive charring typically occurs when hot melt adhesive is exposed to excessive heat and remains in the system for too long without being dispensed. Over time, this leads to thermal degradation and carbon buildup.

Several factors can contribute to adhesive charring in a hot melt system, including:

Running a hot melt system at temperature while it is idle
Operating at temperatures above the adhesive’s recommended range
Exposure to air that leads to adhesive oxidation
Getting contaminants in the adhesive through handling, storage, or system exposure
Not properly cleaning or maintaining the hot melt system
Using low-quality hot melts with poor thermal stability
Using a tank size that is too big and increases dwell time

While there are multiple potential causes of adhesive charring, many instances are preventable with proper product selection, equipment setup, and maintenance.

Signs of Adhesive Charring

Before you can prevent hot melt char, it helps to know the early warning signs of adhesive charring. Hot melt char buildup often develops gradually, so recognizing when it starts can help you avoid costly downtime and equipment damage.

Some signs of adhesive charring include:

Adhesive discoloration such as dark or black hot melt adhesive
Adhesive gelling or thickening
Clogged hoses or applicators
Increased system pressure
Poor bond quality
Equipment failure or increased maintenance needs

If you start to notice any of these problems, it is important to take steps immediately to address them as this can help prevent more severe damage, costly downtime, and reduced equipment performance.

How to Prevent Hot Melt Adhesive Char

Adhesive charring from hot melt can cost you both time and money. It is a pain to troubleshoot and clean. It can also kill your company’s productivity from unnecessary downtime. Instead of dealing with the issue after the fact, try stopping it in the first place. These tips on how to prevent adhesive charring may help.

1. Set the Right Temperature

It is important to run your hot melt at the right temperature. Higher temperatures, especially during idle times, are the biggest culprits of hot melt charring. As an added precaution, a temperature setback can decrease the chances of the adhesive degrading by gradually decreasing the temperature in the unit when it is not actively in use.

2. Perform Regular Maintenance and Cleaning

One of the best ways to avoid adhesive char buildup is to perform regular maintenance and cleaning of your equipment. Make sure you flush your tank regularly when you change adhesives. A product like Red Baron cleaner can help make this process easier.

Along with cleaning the tank, be sure to also keep the hoses clean. Wipe off dust and debris daily. Also, wipe away any hot melt on the hose fittings or the hose braid while wearing safety gloves. This will reduce the likelihood of hot spots in the hose and kinking. While trying to clean out the insides of your hoses sounds like a good idea, it can cause more harm than good. Using a snake will scratch the walls of your hose and cause them to collect adhesive char even faster.

If you are not sure how to clean your machine properly, getting regular hot melt equipment maintenance from a professional is an option.

3. Use the Right Adhesive & Equipment

For optimum efficiency (and to decrease char in hot melt adhesives), you want to ensure that you use the right adhesives, system, and components. While you may save money on bargain products, it could cost you in the long run.

Low-quality, incompatible, or unstable adhesives can degrade and form char more quickly. The wrong size tank could cause your adhesive to sit for too long and burn. Low-quality hoses and machines have shorter work lives and may not be as effective at preventing the buildup of hot melt charred glue.

You may want to consider an inline filter between your gun and hose to trap burnt glue before it clogs your guns or nozzles. You could also go tank-free. The Graco InvisiPac hot melt glue melter, for instance, uses melt on-demand technology that feeds adhesive as needed to significantly reduce hot melt charring.

4. Fill the Tank to the Right Level

Along with using high-quality equipment, you also want to ensure that your hot melt tank is filled to the right level with adhesive. A tank that is low on adhesive will leave residue on the walls that is exposed to oxygen. This combination of heat and oxygen can make glue burn more quickly. Avoid this issue by keeping the tank full.

5. Replace Damaged or Old Equipment or Parts Immediately

Damaged equipment or components can quickly lead to disaster. If you have a hose or applicator that is clogged, it is time to get the replacement hot melt part you need. Old equipment can also become less efficient and lead to adhesive charring faster, but ignoring the problem may only cause more damage with longer downtimes and higher costs.

Let Us Help

Not sure what is best for you? Whether you need a replacement part, maintenance, or a different system, our adhesive experts are here to help. Contact our team today and someone will walk you through your options and help you find the right solution for your specific needs.

Hotmelt.com is not affiliated with the Nordson® Corporation. Nordson® is a registered trademark of the Nordson® Corporation.