Modifications in the bulk and the surface of unbleached lignocellulosic fibers induced by heat treatment without water removal: effects on tensile properties of unrefined kraft pulp

Autor: Andreas Kandelbauer, Franz Schmied, Gerhard Zuckerstätter, Johannes Leitner
Rok vydání: 2012
Předmět:
Zdroj: European Journal of Wood and Wood Products. 71:101-110
ISSN: 1436-736X
0018-3768
DOI: 10.1007/s00107-012-0639-2
Popis: The effects of heating lab cooked never dried kraft pulp from pine and spruce at 5 % consistency to 80, 100 and 120 °C in a pressurized vessel were evaluated based on various fiber and sheet properties. The settings of pH and conductivity in the lab trial were chosen in accordance with operations such as oxygen delignification, alkaline extraction, washing or storage of pulp in an integrated paper mill. It was found that the tensile strength was reduced steadily with increasing temperature. Nuclear magnetic resonance spectroscopy showed that fiber crystallinity and pore size increased at high temperatures compared to the unheated reference. Crystallinity most likely affected the fiber flexibility and thus resulted in less and weaker fiber–fiber bonds. Atomic force microscopy indicated that the amount of precipitated lignin granules on the fiber surface was reduced with increasing temperature. The roughness of the fiber surface did not significantly change with temperature and hence did not negatively influence the tensile strength. It was remarkable that a so called reversed latency was observed. Instead of a decrease in fiber curl with temperature, the fiber became significantly more curled. A large portion of the losses in tensile strength was attributed to the increase in fiber curl and leaching of hemicelluloses from the fiber wall.
Databáze: OpenAIRE
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