Comparison of methods to characterize the penetration of hot melt adhesive into paper

Abstract In the use of hot melt adhesives in the production of paper-based packaging, the controlled penetration of the adhesive is important to obtain rapid setting rates, good bond strength, and the efficient use of adhesive. Measuring adhesive penetration depth has been limited to cross-sectional images, but quantifying the depth of penetration is difficult from these images. No quantitative method is well established in the literature. Four different techniques are compared to quantitatively measure adhesive penetration depth. Two methods involve separating the paperboard from the adhesive layer. Two other methods use of silicone oil penetration and mercury porosimetry to measure the decrease of pore volume after the adhesive is applied. These methods are compared with samples generated for various parameters. Experiments were conducted using a typical hot melt glue on uncoated and coated paperboard sample. Cross-sectional images from Scanning Electron Microscopy (SEM) confirm the penetration of some samples. The accuracy and repeatability of these methods were compared. Because of some issues with trying to repeatably remove the paper layer for the weight and thickness methods, and the time and cost of the mercury porosimeter method, the silicone oil method is a nice method to characterize the adhesive penetration depth.