The epoxy resin adhesive properties: the structure of general epoxy resin contains hydroxyl and ether linkage, which makes it high adhesion. Because of these polar groups, its adjacent interface will generate electromagnetic force. With the chemical action of the curing agent, the epoxy adhesive can further produce hydroxyl and ether linkage in the curing process, which not only has high cohesiveness, but also has strong adhesion. Therefore, the epoxy adhesive has strong bonding strength with many materials such as metal, plastic, glass, wood, fiber, etc., commonly known as "all-purpose adhesive".
The epoxy resin has tightly packed molecules, so no low molecular substances will be precipitated in the curing process. Besides, it can be prepared into a solvent-free adhesive, so its shrinkage rate is low in general. If proper fillers are selected, its shrinkage can be reduced to 0.1-0.2%.
There exist stable benzene ring and ether chain in the chemical structure of epoxy resin, as well as the compact structure after curing, which determines curing agent for epoxy resin's strong resistance to the atmosphere, humidity, chemical medium, bacteria, etc. Therefore, it can be applied in many extreme environments.
The epoxy adhesive has high adhesion strength, low shrinkage rate and stable size. Besides, the epoxy resin adhesive will not produce any low molecular substance in the curing process and its coefficient of linear expansion is less affected by temperature. Therefore, products bonded by the epoxy resin adhesive will be stable dimensionally. The cured products of epoxy resin adhesive have excellent electrical insulation properties, with the volume resistivity of 1013-1016 Ω· cm and the dielectric strength of 30-50 Ω· cm KV/Mm. As for the molecules, the epoxy resin contains ether bonds, the molecular chains are closely arranged, and its crosslinking density is high, so it has good solvent resistance, oil resistance, acid resistance, water resistance and other properties, especially strong alkali resistance. The epoxy resin is soluble in and even reacts chemically with many rubber (elastomer) and thermoplastic resins. It has a good dispersion with fillers and can change the properties of epoxy resin adhesive in a large range. Furthermore, it has good manufacturability, high usability, low toxicity and low harmfulness. However, various benzene rings and heterocyclic rings in the resin structure, poor molecular chain flexibility, and uneasy deformation of its cross-linked structure after curing, all of which lead to the poor tenacity, high fragility, low peel strength and vibration resistance of epoxy resin adhesive.
According to the above information, we can know that the epoxy resin has good comprehensive mechanical properties, especially high adhesion, low shrinkage, good stability and excellent electrical insulation, which provides a material basis for adhesive, composite matrix, coating powder and other products.