Curing process of adhesive

Adhesives are cured by physical methods such as solvent volatilization, emulsion condensation and melt cooling and chemical methods.

(1) Hot Melt Adhesive: the polymer melt can be cured by cooling after wetting the sticky surface.

(2) Solution adhesive: With the volatilization of the solvent, the concentration of the solution continues to increase, gradually reaching a certain strength of curing.

(3) Emulsion glue: Because the water in the emulsion gradually permeates into the porous sticky and volatilizes, the concentration of the emulsion continues to increase, and finally due to the effect of surface tension, the polymer colloidal particles condense. When the ambient temperature is high, the emulsion condense into a continuous film, and when the ambient temperature is low and the minimum film forming temperature (MFT), the white discontinuous film is formed. Emulsion adhesives are mainly copolymers of polyvinyl acetate and its copolymers and acrylates.

(4) Thermosetting adhesive thermosetting resin multi-functional monomer or prepolymer polymerization reaction, with the increase of molecular weight at the same time, the molecular chain changes and crosslinking, forming insoluble non-melting gelation or basic curing. In a certain range, the extension of curing time and the increase of curing temperature are not equivalent, and the reduction of curing temperature is difficult to be compensated by the extension of time. Because a certain chemical interaction needs to occur between the adhesive and the surface of the adhesive, it is necessary to have a high enough temperature to carry out.

Curing pressure:

It is beneficial for the adhesive to fully infiltrate the surface. It is beneficial to eliminate the low molecular volatiles produced by the adhesive curing reaction. It is beneficial to discharge the remaining volatile solvent in the rubber layer. It is beneficial to control the thickness of rubber layer. Adhesives with high viscosity tend to have thicker adhesive layers, and the adjustment of curing pressure controls the thickness range of the adhesive layer.

It is left for a period of time after gluing, which is called precuring. When the viscosity of the adhesive liquid becomes large, apply pressure to ensure the uniformity of the thickness of the adhesive layer.

Curing temperature:

The curing temperature is too low, the crosslinking density is too low, and the curing reaction is not complete. The high curing temperature is easy to cause the loss of adhesive liquid or the embrittlement of the adhesive layer, resulting in the decrease of bonding strength. Heating is conducive to the molecular diffusion between the adhesive and the adhesive, and can be conducive to the formation of chemical bonds.

(1) Oven direct heating method: use a blast device to make it evenly heat transfer.

(2) External heating method: the heat is quickly transmitted to the inside of the rubber layer, which greatly reduces the curing time. Acoustic heating method: for viscoelastic adhesives and solvent-free adhesive, it is not suitable for thermosetting rigid adhesives.