Effect of Adhesive Properties on Film Quality

The effect of adhesive properties on film quality mainly refers to the influence of the relative molecular mass and relative molecular mass distribution of adhesive cohesion energy, as well as the internal stress, viscosity value, and surface tension of the adhesive on the bond strength.

Adsorption theory believes that the size and quantity of polar groups of the binder's host material are proportional to the adhesive strength of the binder, but the practice of coating production shows that this view is only applicable to the bonding of high surface energy adherends. For low-energy surface adherends, the increase in the polarity of the binder tends to reduce the diffusibility of the segment due to its group constrained to each other, resulting in a poor wetting of the binder and a decrease in the bond strength. Because the plastic film and the printed matter are different in the film production, their surface energy is not the same. Therefore, different adhesives should be used.

Under normal circumstances, the bonding strength increases with the increase of the relative molecular mass, and gradually increases toward a certain value after a certain range. If the relative molecular mass is too large, the wetting ability of the viscous agent decreases, and the adhesive strength is severely reduced; the viscosity of the binder has a great influence on the fluidity, wettability, uniformity of the coating, and the like of the binder. Therefore, in the process of coating, drying, compounding, etc., the change of viscosity will affect the bonding strength; the surface tension of the adhesive is also an important factor affecting the wetting and penetration of the adhesive. In actual production, adhesives with high adhesive strength are often used, and a small amount of surfactant is added thereto to appropriately lower the surface tension of the adhesive.