Ask Dr. Dave: November 2013
Are epoxy adhesives with short cure times strong and durable?
Question: I see many so-called “five-minute” epoxy adhesives (and sometimes ones with even shorter cure times). Are these adhesives truly strong and durable?
Answer: These adhesives are used quite widely in many industrial and consumer applications. They are usually 1:1 mix systems of adhesive and hardener that have been packaged in user-friendly packages, such as a twin syringe or cartridge. In addition, they often come with a static mixer tube, which eliminates the need to mix the two components after dispensing. (Older readers will remember the days when epoxies came in two cans or tubes, and both measuring and mixing were required.)
If you read the data sheet or the instructions on a consumer package, you will see that the five minutes refers to the gel time; that is, the time when the mixed adhesive becomes immobile. Full cure typically takes up to 24 hours, although parts can often be handled much sooner. The other major benefit of these adhesives is that the hardener is based on relatively non-toxic and non-corrosive chemicals.
These adhesives can give high adhesive strengths, and I have no hesitation in recommending them for many household or industrial applications, but some limitations do exist. Like all epoxies that are cured at ambient temperatures, they tend to have limited high-temperature resistance. They are also not very resistant to severe environments, such as continuous immersion in water, although some special versions perform much better than others. In order to achieve maximum performance from an epoxy adhesive, it is necessary to use hardeners that contain more hazardous chemicals, but these can be handled safely with appropriate equipment and personal protective measures.
Any views or opinions expressed in this column are those of the author and do not represent those of ASI, its staff, Editorial Advisory Board or BNP Media.