Three stages of epoxy resin curing agent
1. Liquids - Operating time
Operating time (also working time or service life) is a part of curing time. After mixing, the resin/curing agent mixture is still liquid and can work and be suitable for application. In order to ensure reliable bonding, all construction and positioning work should be done well in curing operation time.
2. Gel - entry curing
The mixture begins to enter the curing phase (also known as ripening stage), when it begins to gel or "mutate". At this time, epoxy is not likely to work for a long time, and will also lose its stickiness. At this stage, it can not be interfered with. It will turn into a hard rubber soft gel, and you will be able to press it with your thumb. Because the mixture is only partially cured at this time, the newly used epoxy resin can still be chemically linked to it, so the untreated surface can still be bonded or reacted. In any case, these abilities of near-cured mixtures are decreasing.
3. Solid-Final curing
When the epoxy mixture reaches the solidification stage, it can be sanded and shaped. By this time you can't press it with your thumb. At this time, the epoxy resin has about 90% final reaction strength. Therefore, the fixing clamp can be removed and kept at room temperature for several days and it continues to solidify.
Curing time of epoxy resin
is related to curing temperature. Generally speaking, under the same curing agent, the higher the temperature, the shorter the curing time. In order to meet different industrial applications, epoxy resins produced in the market now have curing time of several minutes and one or two hours (under normal or heating conditions). Others can be completely cured at room temperature for more than ten or dozens of hours, and some single-component UV-curable glue, the main component of which is epoxy resin. The curing time is only tens of seconds to two to three minutes by UV irradiation.