Laboratory scale measurement procedure for the runnability of a wet web on a paper machine, part 2

In the second part of the series we further link wet paper results of fast tensile test rig IMPACT with paper machine runnability. This paper presents the effects of filler and Kraft content, refining level, jet/wire ratio, and strain rate on the tensile and relaxation properties of a wet web. Since relaxation occurs in all papers subjected to a constant strain increase, the key item is the tension holding capacity of paper. It depends naturally on draw levels, but also greatly on properties of furnish, including its numerous modification possibilities at different raw material handling and stock preparation stages. The effect of the filler content on hand-sheets in-plane tensile and relaxation properties were shown to be strongly dependent on dry solids content. Filler content level was shown to affect more wet web tensile than relaxation properties. The relationship between density and tensile strength of dry paper was shown to be linear. Wet paper tensile strength and residual tension were not developed linearly by increasing density. In order to evaluate wet web runnability, both residual tension and dry solids content of paper should be observed. The effect of the jet/wire ratio was similar on both wet and dry MD/CD tensile strength ratios, whereas at constant jet/wire ratio the MD/CD ratio of residual tension was significantly higher. This was mainly due to low elasticity of wet web in CD. Strain rate were shown to have significant effect on stress relaxation percentage as well as the maximum tension of wet paper.