Recycling Behavior of Mechanical and High Yield Pulps Made from Aspen, 1994 Pulping Conference Proceedings

K. N. Law, J. L. Valade, J. Quan

Changes in pulp characteristics of aspen mechanical and high-yield pulps and black spruce thermomechanical pulp during repeated drying-rewetting processes were examined. The results obtained indicated that loss of hygroscopicity, as a result of drying-rewetting, occurred in all pulps and was irreversible even in mechanical pulps of both aspen and black spruce. The loss in hygroscopicity was accompanied by a drop in fiber bonding strength. The fall in fiber bonding strength only occurred in aspen pulps; spruce TMP showed an increase in fiber bonding strength. Mechanical pulps from both aspen and black spruce showed increases in sheet density, while all the chemically treated aspen pulps suffered decreases in sheet density as a result of recycling. Intrinsic fiber strength of all pulps studied was improved by the drying-rewetting process up to 5 cycles. Aspen commercial ultra-high yield pulps behaved differently, in some aspects, from those prepared in the laboratory. Future research should be directed at studying not only the influences of chemical treatment but also the mechanical refining Chemimechanical pulp, Chemithermomechanical pulp, Lignin content, Mechanical property, Optical property, Picea, Populus, Recycling, Sulfonate content, Thermomechanical pulp, Water retention value.