Abstract
When a kraft pulp is repeatedly wetted in water and dried for several times, the strength properties of handsheets are considerably deteriorated. The repeated wetting and drying of a recycling process affects the microstructure of the pulp fibers. The shrinkage of internal pore structure under recycling was not easily reversed.
Thirty-three 9-year-old fast-growing individual trees of Eucalyptus globulus planted in Australia were examined to investigate variations in pulp fiber and handsheet properties during recycling. Large between-tree variations in the thirty-three individual tree pulps were observed in tensile strength of handsheet during recycling. The fiber wall thickness and the Runkel ratio well reflected the shrinkage configuration of the pulp fibers during recycling.
Tensile indices at expected recycling were calculated by nonlinear regression analysis for each pulp. Expected tensile index of handsheet at extended recycling were closely related to the sheet density after five recycles, the fiber swelling of original pulp and fiber morphological characteristics.
Three species of11-year-old fast growing Acacia woods, namely Acacia mangium, Acacia auriculiformis and Acacia mangium×Acacia auriculiformis (hybrid) , planted in Malaysia were also examined to investigate variations in handsheet properties during recycling.
Variations in tensile strength of handsheet of the hybrid during recycling were similar to those of Acacia mangium. On the other hand, handsheet from Acacia auriculiformis had lower tensile strengths during recycling than other two species. The hybrid showed higher expected tensile indices, compared with other two species.
