The Effect of Twist on the Strength of Paper Yarns: The Case of Paper Made from Softwood Pulp

Recycling of cellulosic materials is increasingly important in developing the circular economy where fibres must have more than a single usage. The recycling cellulose-based textile fabrics has its own challenges in terms of sorting and shredding while the resulting material can be transformed only into a lower grade material. One alternate route is to manufacture paper from the cellulosic material, then transform it into yarn and textiles. As part of establishing that greater sustainability, softwood paper, treated with 1% by mass of Nadavin DHN resin, was used to manufacture paper yarns. Initially, paper ribbons were cut from a range of standard grammage papers and then ‘compressed’ using a condenser and different levels of twist introduced on a conventional winding machine. It was found that the grammage of the paper ribbon and the twist per unit length imparted during yarn formation play an important role in the strength of the resulting paper yarn. Also, paper yarns tend to have maximum strength at an optimum twist value and further increases in the yarn twist result in lower strength. Paper yarn tend to follow a similar behaviour as staple yarns. In addition, the specific strength of paper-yarns tends to decrease with the increase in twist-contraction. As expected, paper of higher grammage is thicker and the resulting yarn is coarser and the length of paper required to achieve a particular number of twists per unit length is longer for heavier paper. In general, the strength of the paper yarns was lower than a comparable cotton staple yarn and to some extent guides the potential application areas for paper yarns.