Epoxy adhesive has excellent performance, wide application, simple process and few investments, and most of its varieties can be used in the field. Therefore, it has been paid attention to by the personnel in the industry, and its research has also been invested in a large number of people, with rapid development. There are many kinds of them, but they are not unified at present. Common classification methods are as follows.
(1) According to the functional classification, it can be divided into general varieties (including room temperature curing, medium temperature curing, high temperature curing and low temperature curing adhesives), functional adhesives, environmental protection adhesives and special adhesives.
(2) According to its professional use, it can be divided into epoxy resin hardener for machinery (such as agricultural machinery glue), epoxy resin hardener for building (such as bonding steel reinforcement glue), epoxy resin hardener for electronic (such as pouring glue), epoxy resin hardener for repair (such as concrete pouring glue), and general glue for delivery, marine glue, etc.
(3) According to the curing conditions, epoxy resin hardener can be divided into four types: high temperature curing (curing temperature ≥ 150 ℃), medium temperature curing (curing temperature 80 ~ 150 ℃), room temperature curing (curing temperature 15 ~ 40℃) and low temperature curing (curing temperature < 15 ℃). Room temperature curing, which is liquid at room temperature, can be completely solidified and reached the usable strength within a few minutes to a few hours at room temperature after the modulation is within 7d. It has great advantages. Its characteristics are: the curing process is simple, easy to use, without curing equipment, so the energy is saved, the cost is low; the use period of room temperature is short, so it is mostly supplied by two components, or it is currently used and matched; generally, the curing strength reaches the applicable strength in 24 hours, the highest strength in 3-7 days, and changes with the temperature.
(4) According to the packaging form, it can be divided into single component glue, two-component glue, etc.
(5) According to the stress condition of adhesive joint, it can be divided into structural adhesive and non structural adhesive. The definition of structural adhesive in the national standard is: a kind of adhesive used for the bonding of stressed structural parts, which can withstand the allowable stress and environmental effect for a long time. According to the standard, the adhesive joint can not only bear, but also transmit large amounts of stress. The joint has high mechanical strength. There is no national standard for the classification of structural adhesives in China. Generally, structural adhesives are divided into high strength and high toughness adhesives and medium strength and medium toughness adhesives according to the stress and bonding strength of the bonding object.
The main properties of epoxy adhesives are as follows.
① High strength and toughness.
② The creep resistance is good, and the creep variable should be very small.
③ It has good fatigue resistance and impact resistance.
④ It has a certain heat resistance.
⑤ It has good medium resistance, atmospheric aging resistance, especially humidity and heat aging resistance.
⑥ Good durability and adequate safety.