Glossary of Cure Time Terms
Cure time, pot life, working life, working strength etc. What do they all mean? So many terms, so many figures, curing time information can be very confusing… Here are some explanations for the common terms used to measure adhesive cure time.
Fixture time: Normally this term is used for a very fast setting adhesive such as a cyanoacrylate, UV-curable adhesive or a very fast setting structural acrylic. It is the time taken to reach the point at which, for example two adherents being bonded together can no longer be “wiggled” (the adhesive sets firm and the parts can no longer be moved independently).
Pot-life: This is valid for 2-part mixable adhesives such as 2-part epoxies or structural acrylics. If you mix resin and hardener together in the correct ratio in a “pot”, the pot life is how long you have from the point of mixing until you need to have used all the mixed adhesive (before the viscosity increases to an unusable level). It is important to remember pot life can be shortened considerably if you are working in a high temperature environment, e.g. at 30°C, the pot life quoted on the technical datasheet is halved (so a 1 hour pot life at 21-23°C will be reduced to 30 minutes). Conversely, if you are working in a cold environment you would end up with a longer pot life allowing more time for mixing and applying adhesive product.
Some people call the pot life “working life or working time” meaning how long you can work with the adhesive before it starts setting hard. This should not be confused with working strength.
Open time is very similar to pot life, it means the time you have from the point of mixing or activating the adhesive, applying it, assembling the parts and closing the joint.
On-part life: this is something normally associated with solvent or contact adhesive where once you have applied and spread the adhesive you only have a certain amount of time to assemble the parts and close the joint. Not observing the recommended time can result in a reduced bond strength. It is also a term which can apply to an activator, such as those used in combination with anaerobic or cyanoacrylate adhesives. After pre-treatment or activation there may be an on-part life limit after which the activator may lose its reactivity.
Handling time: After the adhesive has been applied and the joint assembled and clamped, the handling time is the point at which the clamps can be removed and the joint is strong enough to hold itself in position (although there should be no extra load placed on the joint until it has reached “working strength”.)
Working strength: The time the adhesive takes to reach sufficient strength to be put into light operation. To quantify this, it would be the point where the adhesive is at roughly 60% of its final bond strength. The adhesive joint should not be overloaded or unduly stressed but in normal operation the adhesive should be able to function comfortably.
Full strength or full cure: The time the adhesive takes to build up to its full, final strength. Remember with all these terms, figures quoted on technical datasheets will vary depending on temperature, gap and surface reactivity, so exercise caution with these figures.
For further help and advice, please contact Permabond.