5-minute epoxy – more than the name implies

Recently I received a call for a 5-minute epoxy. In general terms, 5-minute epoxy refers to two-component epoxy that start to set up in around 5 minutes.  But they are not all alike.  Epoxies can vary in viscosity, mix ratio, color, specific gravity, gap fill ability, hardness, elongation, dielectric strength, conductivity, strength, temperature resistance, and adhesion.  Here are a few other misconceptions.

Do 5-minute epoxy adhesives cure in 5 minutes?

No, most two-component epoxy adhesives require a minimum of 24 hours to cure.  Some develop strength for 72 hours or more.

So why do they call it 5-minute epoxy?

I looked up technical data sheets from several major manufacturers of 5-minute epoxies. And found that the terminology is not at all consistent.  Permabond calls it handling strength; other manufacturers say gel time, working strength, or working life.   We define handling strength as the time it takes for the adhesive to achieve 0.3 N mm/mm2 or 43 psi. But other companies may have different limits.

At first glance, this seems a bit willy-nilly that there is no true industry standard in such a technical industry.  But since there are so many factors that affect the cure speed of a two-part epoxy and each application has its own requirements, it is best to determine how much strength is needed before a part can be moved for each manufacturing process.

Cure speed can vary, depending on the product, manufacturer, application, temperature, amount of adhesive used, humidity, the accuracy of mix ratio, appropriate mixing, and the phase of the moon.  Similarly, bonding a small metal clip to a 2″ part requires less handling strength than bonding metal legs to a heavy 6-foot steel cabinet.

Contact Permabond for a recommendation for a product to suit your needs.