Deposition Analysis of Pressure Sensitive Adhesives

In this study, a set of pulps containing different PSA products that were recycled at the Forest Products Laboratory (FPL) pilot plant were analyzed for deposition using the PIRA deposition device at North Carolina State University. The work is part of the United States Postal Service Environmentally Benign Pressure Sensitive Adhesive effort. The deposition device consists of a counter-rotating paper machine wire immersed in a low consistency pulp suspension. The contrast between the deposited PSA and the paper machine wire was increased by selectively dyeing the PSA deposited on the wires. Image analysis was performed on the wires to provide a value of the overall ppm, average size, and size distribution of deposits on the wire. The same pulps were dyed with an adhesive specific dye to increase the contrast between adhesive and fiber and image analysis was performed on handsheets at the FPL. The deposition results were found to correlate in general with image analysis results of the same pulp.