Measuring Pulp Strength Delivery, 2000 Pulping / Process & Product Quality Conference Proceedings

M. MacLeod, B. Stromberg--The determination of pulp strength delivery at a kraft mill includes the production and testing of reference pulps made from the mill’s chips. Although the experimental practices used in chemical pulping research laboratories might be construed as "standard", this contention had not been tested. We did so by providing a common source of wood chips and a set of pulping guidelines to seven laboratories. At each laboratory, duplicate pulps were produced; all were then tested for physical properties at two central laboratories. In six of the seven cases, the tear-tensile results and many other physical properties were within 10% of one another, and the variability between samples from any one laboratory was small. Strength delivery studies performed at a single laboratory can provide a valid comparison of two pulps that have a tear-tensile difference of 10% or greater. Better precision probably requires many more tests. In addition, caution should be used when comparing results produced at different laboratories, and when outside the "conventional" kappa range of 25-35 for softwood kraft pulps.