Reduce Downtime Caused by Adhesive Charring

The impact of adhesive char, nozzle plugs, and hot melt materials on your bottom line

When adhesive properties are altered through thermal and oxidative degradation, the thermoplastic nature of the adhesive is lost, leading to overheating or “charring” of the adhesive. Once char is formed in a hot melt system, it is extremely difficult to remove without taking far-reaching measures.

Adhesive char is the single biggest cause of hot melt equipment failure and downtime for end-of-line packaging and case and carton sealing applications. Overall downtime costs from adhesive char can range from £3,740 (€4,240) to £11,218 (€12,720) per hour/per line depending on the application.


Adhesive char increases operating costs

Traditional hot melt systems feature a heated tank to maintain large volumes of molten adhesive for hours or days at a time. Along with varying fill levels, these long heat soaks negatively impact adhesive consistency, producing hard clumps of adhesive char.

These hard clumps of charred adhesive cause plugging in hot melt hoses and dispense nozzles, leading to unplanned downtime that negatively affects the productivity of the manufacturing process. It is common for line operators to keep a surplus of replacement nozzles to hand to help minimize downtime.

The financial consequences of adhesive char

Layers of char build-up inside a hot melt hose make it harder to maintain consistent glue viscosity through the entire system. As a result, hoses must be replaced more frequently. If adhesive char is a common problem, it will also get into the system’s pump and ultimately lead to premature failure of fluid seals in pumps and guns.

Depending on the production process, the profitability impact of adhesive char can be significant. Some examples of hard costs from char-related issues (not including related downtime):

  • £450 (€500)- £900 (€1,025): hot melt hose replacement at £75 (€100) per foot (30cm)
  • £1,125 (€1,275)-£3,750 (€4,250): pump replacement and rebuild process
  • £5,250 (€5,950)-£10,500 (€11,900); capital cost for additional units

Layers of charred hot melt adhesive can build up inside hoses

Adhesive char build-up in a traditional, tank-based hot melt system

Downtime Caused By Cleaning Hot Melt Nozzles & Tanks

Heated tank systems often require routine cleaning and maintenance to avoid excessive char build-up. These cleanouts are labor-intensive and time-consuming, further affecting uptime and productivity.

Manufacturers may have to take tanks offline to completely scrape the adhesive char build-up from the inside of a tank. These tank scrapes can take at least half a day to accomplish – resulting in labor and overhead rates from £750 (€850) to £1,125 (€1,275). Companies not equipped to do the tank scrape in-house may have to send the tank out to have the char removed, adding refurbishing and shipping costs, as well as additional lost uptime.

Once the system is cleaned of char, the tank-based technology wastes valuable uptime reaching operating temperature. To avoid costly downtime during normal production, operators will often leave hot melt tank systems on (even when a plant is shut down), wasting energy and further reducing profitability.

New melting technology eliminates adhesive char

Instead of traditional tanks, new hot melt systems using Tank-FreeTM technology use specially designed melting chambers. The elimination of heated tanks improves hot melt equipment performance dramatically. By providing a greater melting surface, these melters are more efficient and provide significantly faster heating times – achieving operating temperature in 10 minutes or less compared to start-up times of at least 45 minutes with traditional hot melt tanks.

What you gain by applying new melting technology

The shortened exposure of the adhesive to heat in these systems also reduces the amount of char formation within the system. Less time at temperature results in less adhesive char. With a minimal melted volume, hot adhesive is dispensed quickly and replenished with a fresh supply.

  • The reduction of char leads to:
  • Less material waste
  • Fewer nozzle plugs
  • Less overall system maintenance
  • Longer fluid seal life
  • Less production line downtime

Expanding hot melt material options

Certain hot melt adhesive materials are usually not even considered due to their tendency to char with traditional heated-tank systems. To deal with the negative impacts of adhesive char formation, some manufacturers have switched to more expensive, temperature-stable adhesives. While these adhesives may be a good option to consider, the increased cost often impacts profit margins. Ultimately, hot melt equipment should never dictate adhesive choices.

The newly designed melting chambers in the new Tank-Free systems have increased the viability of potential hot melt adhesive options, including metallocene, EVA, and others. These adhesive options provide increased affordability and help manufacturers increase end-of-line packaging profitability.

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