Prediction of wet web runnability with a relaxation test

A tensile test rig has been developed by VTT and Metso Paper for measuring dynamic tensile and relaxation properties of wet and dry paper. Hand sheets made of mechanical and chemical pulps were tested in this study at strain rate 1000%/s. The main interest in this study was in the effect of softwood pulp on the residual tension and wet web runnability. Results show that dry strength properties of pulp mixtures do not predict its wet web runnability. Additionally, these results call in question the generally accepted role of softwood chemical pulp in wet web runnability