3M: Adhesive Cartridges

Shawn Collins from 3M products sat down for a one-on-one discussion on adhesive cartridges. You will find useful information on shelf life, partially used cartridges, expandable foam, and curing issues.

Question: What is the shelf life of a 2-part cartridge?

Answer: The general rule of thumb is: 2-part urethane products have a 12-18-month shelf life and epoxy products have an 18-24-month shelf life, depending on the specific product. 3M 2-part products specify the chemistry type (epoxy technology or urethane technology) on the front label. Shelf life is approximate due to the many factors involving shipping and storage. Always store these products in a cool, dry location for maximum shelf life.

Question: Is the cartridge shelf life decreased if it is opened and partially used?

Answer: The shelf life of a partially used cartridge should not be affected if the mixing nozzle is left on the cartridge after the previous use. The mixed material in the nozzle will cure and seal out air and moisture to preserve the remaining material in the cartridge. If the material is within the shelf life and there are no visible signs of cured material when you extrude out a small amount to equalize the cartridge, the remaining material is viable for use. Material that is approaching or beyond the shelf life may contain crystalized or hardened material, or show signs of thickening and increased viscosity, and should not be used.

Question: Expanding foams seem to harden in the cartridge after being used even if I leave the nozzle on, what can I do to prevent this?

Answer: Expanding foams are unique because the foam can continue to chemically react even after extruding is complete. For this reason, the instructions in the package state to leave the cartridge, with the nozzle attached, in the applicator gun with pressure on the plungers for a minimum of 5 minutes after use. This will prevent the foam from expanding back into the cartridge and hardening in the outlet ports. The longer pressure remains on the cartridge, the better the results will be. Always check the outlet ports for hardened material before use. Always level the plungers (equalize) before attaching a mixing nozzle because the foam expansion pressure may force a plunger back slightly.

Question: What should I do if the material in a 2-part cartridge doesn’t cure properly?

Answer: First, check to see that the cartridge plungers are evenly lined up with each other. If not, there may be a problem with the applicator gun, or it is the incorrect applicator gun. Next, remove the mixing nozzle and inspect the cartridge for cured material that may be blocking one of the cartridge outlet ports. If cured material is present, remove it with a pick or similar tool. To identify if the problem occurred from improper mixing, extrude a small amount of material onto a mixing board (ensure that the mix ratio of the extruded material is correct, 1:1 or 2:1 depending on the cartridge cylinder size) and thoroughly mix the part A and part B materials together by hand with a filler spreader. Check to see if the mixed material cures according to the cure time and temperature in the instructions. If the material cures, there was likely a mixing or equalizing problem, and the cartridge can be used. If the material does not cure, return the cartridge to the distributor and use a fresh cartridge.

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