There are two types of epoxies that arrive as one component. Single component epoxy contains latent hardeners that are relatively inactive at room temperature. Pre-mixed and frozen epoxies also arrive as one component but may not require heat to cure. For our purpose, we will be discussing single component epoxy that does require heat to cure.
Technical data sheets often give several examples; 130°C (266°F) for 60 minutes or 150°C (300°F) for 45 minutes. Let’s say you have a curing oven already set at 140°C (284°F) it isn’t too difficult to guess that cure will take 50 to 55 mins.
One part epoxies, (also called single part epoxies, one component epoxies, 1K or 1-C or heat cured epoxy) contain latent hardeners. Latent hardeners are mixed into the epoxy resin and have very limited reactivity at ambient temperature. They react at elevated temperatures to cure the epoxy adhesive.
Although the epoxy adhesive products Single component epoxy and cure schedules can be modified to meet specific requirements, standard minimum threshold to achieve cure is 107°C. Low cure temperature epoxies have been developed that reduce that threshold to 80°C. The maximum curing temperature for heat activated one part epoxies is 300°C. As you likely guessed, higher cure temperatures require shorter cure time.
Technical data sheets will provide cure time / temperature guidance for single component epoxy. It is important to know that the times listed generally indicate the length of time the adhesive is at temperature. There can be a significant difference between the time the assembly goes into the oven and the time the epoxy adhesive reaches the desired temperature – especially on large assemblies or assemblies with adhesive at the center. Similarly, filling a hot oven with cold metal parts will temporarily reduce the oven temperature.
Induction curing is likely the fastest way to cure single component epoxy. The metal part itself is exposed to current and heats. Cure is generally accomplished in <3 minutes. For some, this is a very efficient cure method. Other heat sources include the traditional conventional oven, as well as infrared lamps, hot plates, or hot-air guns.
In addition to time and temperature, viscosity and rheology of the epoxy adhesive should be considered. Single component epoxy is designed to either stay in place during the cure process or to flow as they begin to warm before they start to set. Flow characteristics range from products with no flow (often called Non Sag) to products that are free flowing as they approach cure temperature to a variety of controlled flow products in between.
Contact us for more information on one part epoxies and other epoxy adhesives.