Abstract

The morphological and chemical characteristics of wood fibre cell walls govern their response to mechanical pulping processes like thermomechanical pulping (TMP) and thus determine most pulp and paper properties. Therefore for understanding fundamental aspects of TMP property development, a suitable method should be employed for characterizing morphological and structural changes at the cell wall level due to mechanical and other pre-treatments (e.g. temperature) during pulping processes. In the present work, TMP fibres were characterized according to micro/ultra-morphological changes reflecting cell wall delamination/internal fibrillation (D/IF) as a response to different TMP process conditions. Industrially produced (Holmen Paper, Braviken, Sweden) never-dried TMP pulp samples with varying pulp properties produced under different process conditions were used in the study. A modified method of Simons’ stain that addresses different levels of D/IF of the pulp fibre cell wall was developed. The stain was used to visualize unbeaten fibres that stain blue from beaten/treated pulp fibres that stain orange/yellow where D/IF of the cell wall has occurred. Whole fibre population of the pulp were categorized into five different sub-fibre populations based on their response to Simons’ stain where fibres stained with different intensities from blue to yellow/orange reflecting five levels of severity of fibre wall damage and/or D/IF (i.e. from none to high). Light microscopy was used to identify the sub-fibre populations. Data from these sub-populations were statistically analysed using the nonparametric statistical procedure Ordinal Logistic Regression to assess differences in the degree of D/IF for different pulp types. Transmission electron microscopy (TEM) was used to visualize features of D/IF of the fibre cell wall at the ultrastructural level. Results from statistical analysis using SAS showed there was a significant effect of refining pressure (p value- 0.0054) on the degree of cell wall D/IF of pulp fibres, while energy input at a given pressure level had the most significant effect (p value- < 0.0001). Simons’ stain was successfully employed to statistically compare different pulp types for the degree of D/IF caused by different process conditions and the results gave fundamental reasons related to pulp property development such as tensile index. Results of Simons’ stain on Bauer McNett fractions (10, 30 and 50 mesh) of the pulp type 6,4_1660 showed a clear trend for the severity of cell wall D/IF among different fractions. There was a very high significant difference on the degree of D/IF (p value- < 0.0001) among different fractions with 10, 30 and 50 in increasing order. Furthermore, results showed that the degree of D/IF correlated well with the tensile index of the pulp. TEM studies on fibres from fraction 30 having none, low and high degrees of cell wall D/IF are currently being conducted. It is concluded that the present method of using Simons’ stain for characterizing mechanical pulp fibres can successfully be applied in mechanical pulping processes leading to an improved understanding of the fundamentals behind pulp property development due to different treatments

Published in

Title: 1st Symposium on Biotechnology Applied to Lignocelluloses : March 28th - April 1st 2010 : Lignobiotech One Symposium
Publisher: French National Insitute for Agriculture Research (INRA)

Conference

1st Symposium on Biotechnology Applied to Lignocelluloses: Lignobiotech One Symposium

SLU Authors

• Fernando, Dinesh

  • Department of Forest Products, Swedish University of Agricultural Sciences
    

• Daniel, Geoffrey

  • Department of Forest Products, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Forest Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/28983