Please cite this article in press as: Chinga-Carrasco, G., et al., Structural quantification of wood fibre surfaces—Morphological effects of pulping and enzymatic treatment. Micron (2010), doi:10.1016/j.micron.2010.03.002 ARTICLE IN PRESS G Model JMIC-1479; No. of Pages 12 Micron xxx (2010) xxx–xxx Contents lists available at ScienceDirect Micron journal homepage: www.elsevier.com/locate/micron Structural quantification of wood fibre surfaces—Morphological effects of pulping and enzymatic treatment Gary Chinga-Carrasco ∗ , Per Olav Johnsen, Karin Øyaas Paper and Fibre Research Institute (PFI AS), Høgskoleringen 6b, NO-7491 Trondheim, Norway article info Article history: Received 3 November 2009 Received in revised form 9 March 2010 Accepted 9 March 2010 Keywords: Pulp fibres Microscopy Computerized image analysis Surfaces ImageJ abstract Wood fibres have been utilized by our society as an important component of paper products and are presently gaining more interest as reinforcement in composite materials. During the last decades biochemical treatments have also found applications in the processing of wood fibres. The chemical, mechanical and biochemical treatments affect the morphology of the fibre wall structure at the micro- and nano-level. In this study, we present a modern approach where field-emission SEM (FE-SEM) and relevant computerized image analysis are applied to quantify the fibre wall characteristics. Details such as surface roughness and texture of the fibre walls are quantified objectively. Global polar plots are gen- erated, which are considered to represent the fingerprint of a given pulp. The approach offers a novel perspective in the characterisation of surface structures, moving forward from performing subjective evaluations to performing objective quantifications of wood pulp fibre surfaces. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction 1.1. Wood pulp fibres Tracheids or fibres are the major component in wood (Fig. 1). The cell wall of fibres is composed of several layers, i.e. the primary wall (P) and the secondary walls (S1–S3) (Fengel and Wegener, 1989). The S2 layer of the fibres corresponds to approximately 80–85% of the cellulose matter (see e.g. Krässig, 1993) and is thus a major structural component affecting the fibre properties (see e.g. Jang, 1998; Batchelor et al., 2000). The structural differences between the S1 and the S2 layers are emphasized by the differences with respect to the microfibril orientations. The S2 layers have fibrils oriented in a given direction relative to the fibre axis, e.g. between 0 ◦ and 70 ◦ (see e.g. Page et al., 1972, 1977; Jang, 1998). The importance of the microfibril angle is related to the mechanical properties of the fibres. The lower the microfibril angle, relative to the fibre axis, the higher the strength (Page et al., 1972, 1977). Wood fibres are an important raw material for several indus- try sectors. Wood fibres are processed to manufacture fibres for specific purposes, such as thermo-mechanical, chemi-thermo- mechanical and chemical pulp fibres (Fig. 1, right). Conventionally, fibres have been applied as the major component of paper, includ- ing e.g. tissue, printing paper and packaging. Pulp fibres and their ∗ Corresponding author. E-mail addresses: gary.chinga.carrasco@pfi.no, gch@gcsca.net (G. Chinga-Carrasco). nano-sized fibrils have also been gaining major interest as rein- forcement in composite materials (see e.g. Rials et al., 2001; Nygård et al., 2008; Seydibeyoglu and Oksman, 2008). In recent years, biotechnological applications, using microorganisms or enzymes, aiming at modifications in the fibre material have received increas- ing focus (Viikari, 2002). Such applications open for targeted modifications of the fibre structure. A further biotechnological application is for the complete degradation of the fibre structure aiming at the production of biofuels and chemicals from the sugar monomers. 1.2. Microscopy studies of wood pulp fibres Pulping processes such as thermo-mechanical pulping (TMP), chemi-thermo-mechanical pulping (CTMP) and chemical pulping affect the fibre morphology at the micro- and nano-levels. Several microscopy techniques have been proposed for assessing the qual- ity of pulp fibres, which may be determined by e.g the degree of the fibre wall splitting, fibre wall thickness and collapsibility. Such pulp fibre characteristics may be quantified by e.g. light microscopy (LM) (Kibblewhite and Bailey, 1988), confocal laser scanning microscopy (CLSM) (Jang et al., 1991, 1992; Chan et al., 1998) and scanning elec- tron microscopy (SEM) (see e.g. Kure and Dahlqvist, 1998; Reme et al., 2002). In addition to the fibre cross-sectional characteristics, the sur- face structure of pulp fibres is strongly affected by a given pulping process. Some studies have reported the development of fibre tex- ture depending on the applied pulping process, based on SEM (see e.g. Duchesne and Daniel, 1999, 2000; Fernando and Daniel, 2004; 0968-4328/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.micron.2010.03.002