Nozzles for dispensing adhesives
Some adhesives can be directly applied from the bottle, some may require more accurate nozzles or dispensing needles, and some two part adhesives require static mixing nozzles to mix the two components together to facilitate cure. Here is a brief guide to nozzle selection by adhesive type.
These are single part and do not need a mixing nozzle. Smaller bottles have a built in nozzle which can be trimmed to the preferred diameter to allow accurate dispensing. For bulk material going through dispensing equipment, it is important to use PTFE or PP dispensing tips (metal needles will clog as the adhesive cure will be triggered inside the needle).
Again, these do not require mixing and have a basic nozzle built into the smaller bottles. Very fine “P-nozzles”, plastic tips, taper tips and metal needles available from Permabond, these fit onto the basic nozzle to provide a much smaller controlled droplet. Contact Permabond for further details / ordering information.
Structural Acrylic Adhesives
There are several types of structural adhesive:
Single Part: Dispense in a similar way to the anaerobic adhesives
Bead on Bead: Bottle nozzles can be trimmed (try trim the nozzles on both A & B bottles the same diameter to try to get a 1:1 ratio). If dispensing from a cartridge without a nozzle, position the cartridge so on component lays on top of the other (not side by side). Take care not to cross-contaminate the port – otherwise next time you go to use the adhesive the cap may be bonded on or the port blocked.
Resin & Initiator: Initiator is normally brushed on with a brush, roller or may be sprayed. Resin comes with a basic nozzle which can be trimmed to the desired diameter. Nozzles should be replaced or properly purged if the resin has been sat in them for a while between jobs, this is particularly important for MMA-based adhesives where monomer will be evaporating and this could lead to a reduction in final strength (plus also the adhesive is thicker and harder to apply).
Pre-mix A+B: These require static mixing nozzles. It is important to use a nozzle which fits onto the port on the cartridge – there are several types of fitting, a simple 90° twist, or a slot in nozzle which has a threaded sleeve which is screwed onto the cartridge. The latter is more robust and is normally the choice for larger cartridges. Similar nozzles can also be affixed to larger dispensing equipment where bulk adhesive is being used.
Because structural acrylic adhesives are less sensitive to proper mixing compared with two part epoxies, you can normally get away with a slightly shorter nozzle than you would use for an epoxy. This is good because acrylics usually cure more quickly so it is preferable not to have so much wastage in the nozzle. Acrylics can be used with round or square (quadrant) mixers successfully. Because of additional turbulence found with quadrant mixers, they tend to be more effective, again meaning a shorter nozzle can be used. It is important to follow the adhesive manufacturer’s guidelines for nozzle length / number of mixing elements to ensure adequate mixing.
The instructions for these are similar to the Pre-mix A+B structural acrylics, the cartridge packaging is similar. Epoxies are more sensitive to correct mixing so it is essential to use the minimum recommended length of nozzle / number of elements and the quadrant square mixers do give better mixing. When using a new cartridge, make sure to align the back pistons on the cartridge or purge the first bit of adhesive as it may be resin or hardener rich. If removing the nozzle and replacing the cap, make sure to fit the cap prongs back in the right way round or you risk cross-contamination and may not be able to get the cap off again. Or just leave the old nozzle on to store and replace when you next go to use the adhesive.
These have a basic screw on nozzle which can be trimmed to the preferred diameter. As MS-polymers are moisture cure and will react with moisture in the air, make sure to reseal the cartridge after use (taping the top can help).
UV curable adhesives – again, these come in bottles where the nozzle can be trimmed.
Permabond stocks a wide range of nozzles to go with its products, if you need help and guidance, please contact us and we would be happy to help.