Troubleshooting Single-part Epoxy Adhesive Dispensing Problem
Manual Dispensing from Cartridge
On many epoxy adhesive cartridges, there is a strong plastic stopper. The stopper must be cut with a sharp Stanley knife (or similar implement) before affixing the dispensing nozzle. The dispensing nozzle is normally supplied with the adhesive.
Typically, 320ml cartridges fit in regular caulking guns. However, certain epoxy adhesive products with high viscosity may prove difficult to dispense if pumping by hand, so may require a gun “upgrade” with more sophisticated ratcheting or pneumatically operated by a compressed airline.
Cold Dispensing Conditions
Epoxy adhesive thickens when cold so if you using the adhesive straight from the refrigerator, or are working in a cold environment, it will become a lot more difficult to dispense. Some high viscosity grades may become virtually impossible to dispense from a cartridge. In this case you can warm the epoxy adhesive to reduce the viscosity to something more workable. However, warming the epoxy adhesive will eventually cause it to gel and shorten its shelf life in the cartridge – especially if repeatedly taken out of the fridge, warmed up and then put back in the fridge.
Common Single-part Epoxy Adhesive Dispensing Problems
Epoxy Adhesive not coming out of cartridge:
- Check – the tip has been cut off and the adhesive is visible inside.
- Without putting the nozzle on, try to dispense some adhesive directly from the mouth of the cartridge. It may be necessary to trim the nozzle to a larger diameter to reduce the back pressure in the cartridge to allow the adhesive to be dispensed.
- If nothing is coming out, unfurl a paper clip and poke it into the mouth of the cartridge, see if the adhesive has gone hard.
- If it has gone thick, you can warm it and then see if you can dispense. If not it could be time to get some fresh stock. Be very careful to warm it gently e.g. 30°C and check every 10 minutes. Heating it too much could cause the material to exotherm.
- If the adhesive is still liquid and doesn’t come out, check the gun is functioning properly and the plunger fits properly against the back piston in the cartridge.
- As mentioned, some products are high viscosity and difficult to dispense manually so a more robust, compressed air gun or proper dispensing equipment may be required.
Automatic Dispensing Equipment
As the product is single component and does not require mixing, it lends itself to a simple dispensing equipment set-up, either by automated dispensing from a cartridge or from bulk with a follower plate pushing the adhesive down and forcing it up a tube. If experiencing problems, check the following:
- Ensure machine is switched on and everything is plugged in correctly
- Compressed air supply is operative
- Check for any blockages, ensure adhesive hasn’t gelled in any parts of the equipment
- Check any bulk single-part epoxy adhesive is still liquid and hasn’t thickened (or allow it to come up to room temperature if it is cold fresh from the refrigerator).
- Check the follower plate is the correct diameter for the adhesive packaging (check for any lip or rim which may interfere with the follower plate.
- Check the pipeline and nozzle are the right diameter and are compatible with the rheology of the single-part epoxy.
Top Single-part Epoxy Adhesive Dispensing Tips
- After use, remove parts from dispensing equipment for cleaning, metal parts can be soaked in solvent overnight.
- Bulk single –part epoxy adhesive should be stored in the refrigerator.
- If only using small quantities of epoxy adhesive, it can pay to dispense material from a large cartridge into smaller syringes which can be refrigerated and taken out one at a time for use.
For further help, please contact the Permabond technical team here.