The most typical examples of 2-component adhesives are epoxies (and as of recently, hybrid adhesives) which combine properties of epoxies and cyanoacrylates). Epoxies come in a really wide variety of pack sizes and shapes: from little dual syringes with only millilitres of adhesive in them, all the way to buckets and pails that can contain up to dozens of kilograms of each component.
Much like with cooking, it takes a bit of patience to work the magic and get your two components to merge thoroughly in a chemical reaction that will result in a reliable and durable adhesive. Let’s take the simplest example where mixing ratio is 1:1. It means that each molecule in component A needs one molecule in component B to pair with. Think of it like a dating party to which you invite the same number of men and women and then some of the women don’t turn up. The men that end up without partners may become rather frustrated and will be likely to cause some trouble.
In the same way, if the mixing isn’t thorough enough the adhesive will not cure properly, nor will it develop all the properties it should. It can remain gel-like and the final strength can be reduced leading to risk of failure of the bonded part.
To make sure this doesn’t happen, it’s best to follow a few basic rules:
- Make sure to follow the prescribed mixing ratio religiously. This is easier when dispensing from a syringe with a static mixer because the dosing of components happens automatically as you press out the product.
- When dispensing from a syringe with a static mixer, discard the first few centimetres of dispensed material to secure that the mixing starts properly before using the mixture.
- When mixing components by hand, measure the amounts carefully and always mix a bit longer than advised on the packaging, just to be on the safe side.
- Observe the colour of the mixture: it has to become uniform all through, with no lighter or darker areas.
- Never scrape the product off the walls of the mixing container. It’s almost 100% certain that this part of the material hasn’t been thoroughly mixed.
In cases where precision is really of the essence in both mixing and dosing of the applied product, you can always resort to one of the automated solutions or simple equipment pieces that can be of great help.