How to store and handle hot melt adhesive.

For granulate, pillows, 43 mm sticks, blocks and cartridges used in industrial hot melt guns.

How hot melt is stored and handled decides how it melts, flows and bonds: it has to reach the gun clean, dry and unmixed. Good glue, badly stored, gives bad bonds. We see this first-hand: weak joints, uneven beads and blocked nozzles that have nothing to do with the gun and everything to do with how the adhesive was kept.

Storage: five rules

1. Sealed. Keep hot melt in its original packaging until you load it. Never leave a bag or box open on the floor or the bench.
2. Cool and dry. Away from direct sunlight, ovens, heaters and anything that runs hot. Heat and damp both degrade hot melt before it ever reaches the gun.
3. Off the floor. On a rack or pallet, away from dust and water.
4. Oldest first. Use stock first in, first out, so nothing sits past its shelf life. The shelf life is on the adhesive’s datasheet or pack.
5. Labelled. Keep each glue in its own marked container, especially when you run more than one adhesive.

Handling at the gun

• Never load dirty glue. Dust, fibres, paper scraps or metal in the glue end up in the nozzle and block it. Nothing but clean glue goes into the tank.
• Close the bag after every fill. An open container next to the gun is an easy way for dirt to get in.
• Use a clean scoop. Do not use your hand, or a cup that has been on the floor.
• Fill to the right level. That is about 1.5 cm below the rim on air-driven guns and the MS 200, and just under the feed opening on the MS 80. See how to use a hot melt glue gun.
• Check the glue suits the gun. MS guns take non-reactive hot melt only; air-driven Reka guns are made for glue from 2,000 to 40,000 mPas. Your adhesive’s datasheet gives its viscosity.

Don’t mix glues

Two different hot melts in one tank can change the viscosity and the bond in ways you can’t predict. When you change adhesive, use up or empty the old one first. On cartridge guns (TR 700, TR 70 LCD, TR 80 LCD), flush the nozzle and adapter when you change to a different glue.

PUR needs extra care

PUR (reactive polyurethane) cures with moisture, which is why it comes in sealed cartridges.

• Keep cartridges sealed. Open one only when it goes into the gun.
• Use dry compressed air. Ordinary compressed air is fine, but it must not be humid: moisture in the air speeds up the PUR’s reaction from the back of the cartridge. An oil and water separator on the compressor helps.
• Flush before a long stop. Run a cleaner cartridge through the nozzle and adapter before the gun sits idle, or cured PUR blocks them.

More on this: cartridges and refills.

Signs the glue is the problem

What you see	What to check
Nozzle blocks again and again	Dirt in the glue: containers left open, dirty scoop
Brown flakes in the glue	Glue overheated or held hot too long; see brown flakes
Bond weaker than usual, same settings	Old stock, damp glue, or two glues mixed
PUR setting in the nozzle or cartridge	Humid compressed air, or no flush before a stop

Not sure which adhesive fits your job? Start with hot melt adhesive, in short, or tell us what you are gluing.