An adhesive’s data sheet will detail its storage requirements, but most two-part structural adhesives will last their whole specified shelf life if stored at room temperature in a cool dark place. There are some differences between the chemistries that may impact how they are packaged and stored. For example, both components of a two-part polyurethane adhesive (PU) are hygroscopic, so they are often packed in metal foil bags with desiccants, and these should not be opened until you are ready to use the adhesive.
Some epoxies can crystallise (usually, this is reversible), so take care with storage temperature – temperature fluctuation or extreme cold can be a cause of this. In all cases, it’s best practice to make sure the adhesive is at room temperature before use – unless, of course, it’s being used outside!
Two-part cartridges with static mixing nozzles are a very common packaging
Most structural adhesives are available in packaging that makes handling straightforward; two-part cartridges are common, and some are available in twin-pack sachets, or in separate bulk containers. Other than adhesives supplied in bulk, little direct physical handling of the adhesive will be required, as for example the adhesive can be applied directly from a cartridge through a static mixing nozzle, either manually or by incorporation into semi-automated or fully automated dispensing equipment. This is good news for both process efficiency and health and safety.
Choice of package size will depend a lot on process demands, including volumes used. Once the package is opened, it is best practice to use it up in the space of a shift or a production batch.
You can buy some very specialist adhesives two part adhesives pre-measured into the correct proportions, mixed and degassed, filled into a dispensing syringe or cartridge, and then frozen to stop the cure. There are specific procedures for these pre-mixed and frozen adhesives.
This post is part of a short series on handling and processing two-part adhesives.
