Influence of filler content, jet/wire speed ratio and drying section draws on MD relaxation of wet paper and strength properties of dry paper

The objective of the present study was to determine the effect of filler content and jet/wire speed ratio on the tensile properties of wet and dry paper when the dryer section draws are varied. Oriented super calendered (SC) paper samples were prepared on a pilot paper machine with varying levels of filler content and jet/wire speed ratio, while maintaining constant draw between the press rolls. Never-dried SC paper samples were dried in a laboratory tensile tester and strained at three stages during drying. The apparent relaxation rate of wet paper was found to depend on the initial tension and filler content, but not on the jet/wire speed ratio or the draw history. In terms of dry paper tensile properties, filler content and jet/wire speed ratio had a more dominant effect than the draws performed during drying. Most of the examined strength properties had a minimum value close to unity jet/wire speed ratio and a maximum on the rush side of the unity point. Efficiency factor, previously used to describe changes in inter- and intra-fiber effects on the shape of the tension-strain curve, decreased with increasing filler content, suggesting that filler and a low jet/wire speed ratio reduces bonding and stress transfer efficiency between fibers. The dryer section draws have only limited potential to compensate the negative influence of high filler content on paper tensile properties.