Water-based adhesive penetration into paperboard and coated paperboard

The setting of water-based adhesives in contact with paperboard is important in the production of boxes and other packaging, but the topic has received little attention in the literature. The penetration of the adhesive into the paper surface is important to get good bond strength through mechanical interlocking. The influence of the process conditions and the paper properties on this penetration is lacking. A water-based adhesive was applied to an uncoated and coated paperboard. The coating layer had two latex lev-els. Samples were characterized in terms of air permeability, void fraction, average pore size, and coat weight. The adhesive was applied to the samples in a mechanical press, squeezing a drop between two samples. The penetration of the adhesive was characterized with a silicone oil absorption method that measured the decrease in pore volume after the adhesive had been applied to approximate the pore volume taken up by the adhesive. The bond strength was measured with a peeling test. The penetration depth into uncoated paper did not depend on the application method parameters such as press-ing time, pressure, or initial solids of the adhesive. The penetration depth ranged from 35–40 mm. The penetration into 10 pph latex content coated paper was similar to the uncoated samples, but reduced penetration was observed into the 40 pph latex content coatings. The results were compared to the limiting amount of adhesive that was obtained from the weight gain of the samples and to a simple model that is based on flow in porous media. Peel tests revealed that good penetration was needed, as well as a strong coating layer to obtain high peel forces.