Effect of relaxation during drying on the final sheet properties

Drying experiments were carried out with different drying powers to achieve a better understanding of the drying process and its effect on final sheet properties. The final sheet surface temperature and the rate of drying str ess relaxation increased with the drying power. The trend of drying stress followed the interaction between an increase in the rate of drying stress r elaxation and a decrease in drying time. When bleached kraft pulp (beaten a nd unbeaten) and TMP were compared, the beaten kraft pulp had the slowest r ate of drying stress relaxation and the TMP the fastest rate. The mechanica l properties of final sheets were quite independent of the drying power exc ept for the strain at failure, which decreased with increasing drying power . The results show that there is not a general linear coupling between the drying stress and mechanical properties of paper.