How Important Is The Glue Mix Ratio?
Get the glue mix right!
Many glues, including solvent based glues and structural glue, are intended for use when the glue is mixed with the hardener.
When component A (the glue) and component B (the hardener) are mixed in a specific ratio (referred to as a stoichiometric ratio), a chemical reaction occurs. The ratio of A to B can vary from product to product and can be found on the technical literature for the glue in question.
Different chemistries of glue have different tolerances for mixing errors. Some glues, like two part epoxies are a little tolerant, whereas certain two part structural methacrylate glues are less forgiving!
What can occur if the correct mixing ratio is not used?
Well, the first adhesive property to suffer will be the strength and resistance of the bond. Depending on the chemistry of the glue, other observations may include the glue curing slowly, curing to a rubbery consistency or in many cases, the glue not curing at all!
How can you avoid mixing ratio issues? Irrespective of the type of glue, the technical data sheet for the glue must always be studied in advance of the glue being used. For solvent based glues, the components are measured by volume, not weight. We always suggest that the fully homogeneous glue is poured into the mixing pot, followed by the hardener. Try to use one pot for measuring and mixing.
Two component structural glues are somewhat easier in that they are supplied in pre-measured cartridges. With all cartridge products, the components must be equalized before the static mixer is attached to the cartridge. Equalizing the cartridge is easy. Insert the cartridge into the gun and before attaching the static mixer, extrude both components until they are coming out in the correct ratio for the product. As soon as this is achieved, attach the static mixer. Extrude about 2 cm of glue then start gluing.
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