Compared with other types of adhesives, epoxy adhesives have the following advantages:
(1) Epoxy resins contain a variety of polar groups and highly active epoxy groups, so they are very strong with metals, glass, cement, wood, plastics and other polar materials, especially materials with high surface activity. At the same time, the cohesive strength of the epoxy cured product is also very large, so its bonding strength is very high.
(2) There is basically no low molecular volatiles when the epoxy resin is cured. The volume shrinkage of the adhesive layer is small, about 1% to 2%, and it is one of the varieties with small curing shrinkage in thermosetting resins. After adding filler, it can be reduced to below 0.2%. The linear expansion coefficient of the epoxy cured product is also very small. Therefore, the internal stress is small and has little effect on the bonding strength. In addition, the creep of the epoxy cured product is small, so the dimensional stability of the adhesive layer is good.
(3) There are many types of epoxy resins, curing agents and modifiers, which can be designed through reasonable and ingenious formulations to make the adhesives have the required manufacturability (such as rapid curing, room temperature curing, low temperature curing, water curing, low viscosity , High viscosity, etc.), and have the required performance (such as high temperature resistance, low temperature resistance, high strength, high flexibility, aging resistance, electrical conductivity, magnetic permeability, thermal conductivity, etc.).
(4) It has good compatibility and reactivity with various organic substances (monomers, resins, rubbers) and inorganic substances (such as fillers, etc.), and is easy to modify by copolymerization, crosslinking, blending, filling, etc. Improve the performance of the adhesive layer.
(5) Good corrosion resistance and dielectric properties. It can resist the corrosion of various media such as acid, alkali, salt and solvent. The volume resistivity is 1013-1016Ω·cm, and the dielectric strength is 16-35kV/mm.
(6) The general-purpose epoxy resin, curing agent and additives have many places of production and large output. It is easy to prepare and can be contact-pressed for large-scale application.
The main disadvantages of epoxy adhesive——
(1) When not toughened, the cured product is generally brittle, with poor resistance to peeling, cracking, and impact.
(2) Low adhesion to materials with low polarity (such as polyethylene, polypropylene, fluoroplastics, etc.). Surface activation treatment must be carried out first.
(3) Some raw materials such as reactive diluents and curing agents have different degrees of toxicity and irritation. It should be avoided when designing formulas, and ventilation and protection should be strengthened during construction operations