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Curing process of adhesive

Aug 26,2020 | Views: 21

Curing method: the adhesive is cured by physical methods, such as solvent volatilization, emulsion condensation and melt cooling and chemical methods.


(1) Hot melt adhesive: the polymer melt can solidify by cooling after infiltrating the adhesive surface.

(2) Solution adhesive: with the solvent volatilization, solution concentration increases, gradually reach a certain strength of curing.

 (3) Emulsion adhesive: Because the water in the emulsion gradually permeates into the porous adhesive and volatilizes out, the emulsion concentration increases continuously, and finally, due to the effect of surface tension, the polymer colloidal particles condense. When the ambient temperature is high, the emulsion agglomerates into a continuous film, while the ambient temperature is low and the lowest film formation temperature (MFT), the formation of a white discontinuous film. Emulsion adhesives are mainly copolymers of polyvinyl acetate and acrylate.

 

Curing pressure:


It is helpful for the adhesive to fully infiltrate the surface. It is helpful to remove the low molecular volatiles produced by the adhesive curing reaction. It is beneficial to discharge the residual volatile solvent from the rubber layer. It is beneficial to control the thickness of adhesive layer; Viscous adhesives are often thicker, curing pressure adjustment control of the thickness of the adhesive layer.

 

After gluing, it is left for a period of time, which is called pre-curing. When the viscosity of the glue becomes larger, apply pressure to ensure the uniformity of the thickness of the glue.

 

Curing temperature:

 

The curing temperature is too low, the cross-linking density is too low, and the curing reaction is not complete. Curing temperature is too high, easy to cause the loss of glue liquid or glue layer embrittlement, resulting in the decline of adhesive strength. Heating is conducive to the molecular diffusion between the adhesive and the adhesive joint and the formation of chemical bonds.

 

(1) Oven direct heating method: the air blast device is used to make the heat transfer evenly.

(2) External heating method: the heat is quickly transferred to the inside of the adhesive layer, greatly reducing the curing time. Acoustic heating method: it is not suitable for thermosetting rigid adhesives, but for adhesives with viscoelastic properties and solvent-free solutions.




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