Surface and internal micro/ultrastructure of TMP fibres produced during high-intensity refining elucidate the development of pulp and paper properties

Dinesh Fernando; Dino Muhić; Per Engstrand; Geoffrey Daniel

doi:10.1515/hf.2011.175

Article

Surface and internal micro/ultrastructure of TMP fibres produced during high-intensity refining elucidate the development of pulp and paper properties

Dinesh Fernando , Dino Muhić , Per Engstrand and Geoffrey Daniel

Published/Copyright: December 13, 2011

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From the journal Volume 66 Issue 4

Abstract

Refining during mechanical pulping causes delamination and internal fibrillation (D/IF) of the fibre wall and changes the surface ultrastructure. Fundamental knowledge about these phenomena at the fibre cell wall level helps our understanding of the development of pulp and paper properties, which in turn facilitates the optimization of processes, helping to save energy and improve the characteristics of final products. In the present study, pulps were produced by double-disc (DD) refined thermomechanical processes (DD-TMP) and have been characterized at the fibre cell wall micro/ultrastructural level based on Fernando and Daniel’s method (2010) of Simons’ staining and scanning electron microscopy (SEM). The pulps studied were never-dried Norway spruce DD-TMP from a full-scale mill trial running under different process conditions; a) varying refining intensity, achieved by using a high-intensity turbine segment (HTS) and a standard (Ref) segment from Metso, and b) varying specific energy consumption (SEC). Improved energy efficiency was obtained with HTS segments, giving adequate or better pulp properties with respect to elongation, light scattering, Canadian Standard Freeness (CSF) at a similar tensile index level and lower energy consumption. Energy efficiency was gained through an elevated degree of D/IF and S2 fibrillation with low energy input. Both the SEC and segment designs had a significant impact on elevating the degree of D/IF. Statistical evaluation of fibre development with respect to D/IF gave evidence for improved energy efficiency in HTS refining. Ultrastructural studies on fibre surfaces showed that HTS refining produced better external fibrillation and leads to exposing the secondary S2 wall as fibre outer layer with different ribbon-type S2 fibrillation. Information obtained at the fibre wall level concerning D/IF and surface ultrastructure contribute to the fundamental knowledge about the pulp and handsheet properties and the energy efficiency of TMP processing.

Keywords: cell wall ultrastructure; delamination/internal fibrillation (D/IF); energy efficiency; fibre development; Norway spruce; refining intensity; SEM; S1 layer; S2 layer; Simons’ stain (SS); TMP

Corresponding author. Wood Ultrastructure Research Centre (WURC), Department of Forest Products/Wood Science, Swedish University of Agricultural Sciences, P.O. Box 7008, SE-750 07 Uppsala, Sweden

Received: 2011-6-7

Accepted: 2011-11-1

Published Online: 2011-12-13

Published in Print: 2012-05-01

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Articles in the same Issue

https://doi.org/10.1515/hf.2011.175

Keywords for this article

cell wall ultrastructure; delamination/internal fibrillation (D/IF); energy efficiency; fibre development; Norway spruce; refining intensity; SEM; S1 layer; S2 layer; Simons’ stain (SS); TMP