Minimizing Air Bubbles in Adhesives
Q: Micro air bubbles are finding their way into my dispensing process. Do you have any tips on how to minimize or eliminate air bubbles?
A: If you are ordering adhesive in syringes or cartridges, try storing the syringes or cartridges in an upright position. The cap should be pointed towards the ceiling. Storing syringes and cartridges in this manner allows the air to travel closest to the point of exit.
When you are ready to dispense the adhesive, make sure that the syringe remains in the upright position while you remove the syringe’s cap and attach it to the valve or the syringe needle. Purge the system (while upright) of any air bubbles that may have been produced by screwing or unscrewing the cap or valve. A threaded system has a tendency to introduce micro air bubbles. Purge at a high pressure to ensure that all of the air bubbles are forced out of the syringe or the valve. If you use low pressure, the bubbles may be caught on imperfections and left behind, only to come out during your production at some later time. If you have a long length of tubing between the cartridge and the needle tip, you may need to purge for several minutes to get the air bubbles out of the tube. The best method to reduce the chance of air bubbles is to shorten the distance between the cartridge and the valve. An optimum system will have no tubing at all. Once you have purged the system, you can reduce the pressure to a normal working level.