The significance of the glass transition of lignin in thermomechanical pulping

✍ Scribed by G. M. Irvine

• Book ID: 104736104
• Publisher: Springer
• Year: 1985
• Tongue: English
• Weight: 625 KB
• Volume: 19
• Category: Article
• ISSN: 0043-7719
• DOI: 10.1007/bf00353074

✦ Synopsis

Changing the temperature at which the thermomechanical pulping of wood is carried out may result in si~ificant changes in pulp properties. Such changes are widely attributed to the effect of the glass transition of the li~cmin. Pulping literature references to this effect frequently appear to imply that this transition is manifested as an abrupt softening of the lignin either at a single temperature (the glass transition "point") or over a relatively narrow temperature range. Application of the time temperature correspondence principle of polymer science and the Wflliams-Landel-Ferry equation to laboratory measurements of the transition suggests otherwise: in terms of the response of the lignin material to the very rapid cyclic deformation processes occurring within the refiner, the glass transition is predicted to occur over a temperature interval spanning the approximate temperature range 100-170 ~ within which most thermomechaaical pulping is carried out. The consequences of this prediction are discussed in terms of the likely fracture processes occurring during the refining process. * The author thanks Mr. V. Balodis and Dr. H. G. Higgins for valuable comments on the manuscript