The difficulty of coating epoxy resin is closely related to the viscosity. If the viscosity of solvent-free epoxy resin is too high, or becomes sticky due to low temperature, the coating is difficult. The adhesive surface can be preheated by hair dryer or other means, preheating to 40 ℃ to 50 ℃, so that the viscosity of epoxy resin adhesive after coating is reduced, and it is easy to wet the adhesive surface. If it is solvent-based epoxy resin adhesive, viscosity is too large, can be diluted with the corresponding solvent before coating, conducive to wetting.
1. Number of times of gelatinization.
The number of times of glue coating varies with the properties of epoxy resin and adhesive. Such as solvent-free epoxy adhesive and dense adhesive, generally coated once can be, and most solvent-based epoxy resin and porous adhesive or require a certain thickness of glue layer construction, need to apply glue 2 times 3 times. For multiple times glue, be sure to dry in the head glue table and then brush the next time, do not act too hastily.
2. The amount of glue applied.
The amount of glue applied is also related to the variety of epoxy resin and the type of adhesive. For porous stickies, the amount of glue should be larger. The amount of glue directly determines the thickness of the adhesive layer, the thinner the adhesive layer is, the less the defects, the smaller the deformation, the smaller the internal stress, the higher the bonding strength, the thinner the adhesive layer is, the thicker the adhesive layer is, the more harmful it is. Therefore. Under the premise of ensuring that there is no shortage of glue, the adhesive layer should be as thin as possible. It is generally considered that the thickness of adhesive layer should be controlled in 0.08~0.15mm.
3. Coating method.
The method of coating is different according to the morphology of epoxy resin. For liquid, paste or paste epoxy resin adhesive can be brushed, sprayed, dipped, scraped, rolled, injected, etc.
Brush coating method.
In this method, the glue is coated on the surface of the adhesive with a brush.
With the help of dry compressed air, the glue is sprayed on the bonding surface with a special glue gun. The spraying is characterized by uniform thickness of adhesive layer, high production efficiency and suitable for large area bonding.
This method is a process of dipping the adhesive into the epoxy resin solution.
The method is a scraper in which paste or paste epoxy resin glue is scraped onto the bonded and sealed parts.
Rolling coating method.
In this method, the roller is first immersed in the glue, and then transferred to the surface of the required bonding or coating. When gluing on the surface of a wide flat object, it is more convenient to operate with a cot. The film coated by rolling is more uniform and has no flow hanging phenomenon, but the edges and corners are not easy to roll. It needs to be patched with a brush.
This method uses epoxy resin adhesive through a special container, with manual, mechanical, pneumatic and other pressure into the joint, waiting for the state or the need to seal the element and so on.
No matter what kind of glue coating method is used, it should be carried out carefully and carefully, which requires that the glue should be coated uniformly and consistently, and avoid air mixing, and finally get a glue layer with appropriate thickness after no leakage coating, no lack of glue, no bubble, no stacking, and proper thickness after bonding. If the viscosity of epoxy resin adhesive is too large, the viscosity can be reduced properly by heating or formula improvement, and the infiltration and permeability of epoxy resin can be improved, so as to ensure the bonding strength. As far as the coating surface is concerned, in principle, each adhesive surface should be evenly glued to ensure adequate infiltration, but for bonding with large area and low strength, the method of point coating, line coating or point and line coating can also be used. This saves both glue and labor.