At present, the basis for the definition of adhesives in our country is still not determined, and there is no uniform standard for its classification. Therefore, high-temperature epoxy resin adhesives maintain the required bonding structure strength in a certain period of time, its medium, and temperature. Or strength retention rate. The high temperature resistance of epoxy resin adhesive mainly depends on the thermal oxidation stability and thermal deformation stability of the cured product. The former determines the use temperature limit of the adhesive, and the latter determines the chemical mechanical properties of the adhesive at high temperatures. Therefore, the main factor affecting its high temperature resistance is the mutual reactivity between the molecules of the epoxy resin adhesive and the molecular structure.
1 Thermal oxidation stability of epoxy resin
Under normal circumstances, the shorter the molecular distance and the higher the density of the cured adhesive, the better its high temperature resistance. The more heat-resistant rigid groups on the molecular chain of the cured product, the greater its high-temperature resistance chemical and mechanical properties, but at the same time, the better the heat resistance of the adhesive, the greater its brittleness. The brittleness of high-temperature epoxy resin will affect the bond strength, so it is usually toughened when the epoxy resin adhesive is installed. Thermal oxidation stability refers to the ability of cured epoxy resin to improve oxidative damage, which is closely related to the molecular chemical structure of epoxy resin. During the preparation process, the molecular structure strength can be improved by adding antioxidants.
2 Thermal deformation stability of epoxy resin
Thermal deformation stability is an important performance requirement for the high temperature requirements of epoxy resin cured products. Generally speaking, the temperature resistance of epoxy resin adhesives is high, and the activity of the curing agent and epoxy resin will be relatively low. Therefore, for epoxy resin adhesives that work at high temperatures, during the preparation process, only the molecular structure of the cured product is completely cured, so that the epoxy resin adhesive has strong temperature resistance