Holzforschung 2016; aop *Corresponding author: Benoît Arnoul-Jarriault, Laboratoire de Génie des Procédés Papetiers(LGP2), Grenoble-INP Pagora, CS10065, 38402 Saint-Martin-d’Hères Cedex, France, Phone: +33 4 76 82 69 74, e-mail: benoit.arnoul-jarriault@pagora.grenoble-inp.fr Raphaël Passas, Dominique Lachenal and Christine Chirat: Laboratoire de Génie des Procédés Papetiers(LGP2), Grenoble-INP Pagora, CS10065, 38402 Saint-Martin-d’Hères Cedex, France Benoît Arnoul-Jarriault*, Raphaël Passas, Dominique Lachenal and Christine Chirat Characterization of dissolving pulp by fibre swelling in dilute cupriethylenediamine (CUEN) solution in a MorFi analyser DOI 10.1515/hf-2015-0167 Received July 27, 2015; accepted November 5, 2015; previously published online xx Abstract: The swelling of dissolving pulps has been inves- tigated by a new method based on the Morfi R analyser, which is measuring the width variation of thousands of fibres in a cupriethylenediamine (CUEN) solution in a few minutes. Pulps from various origins were analysed coming from softwood, birch wood, eucalyptus wood, kraft pulps, sulphite pulps and ECF and TCF bleached pulps, which were modified by several treatments including chemical (cold caustic extraction, hypochlorite) or enzymatic (cel- lulase) methods. The swelling was much affected by the crystalline form of cellulose and the hemicellulose content but did not depend neither on the cellulose DP nor on the fibre structure (hardwood vs. softwood). The dissolving pulp reactivity in the viscose process was also assessed by swelling in dilute solutions of cupriethylenediamine (CUEN) instead of the Fock’s method. Keywords: cellulose swelling, cupriethylenediamine (CUEN), dissolving pulp, fibre morphology, Fock’s reactivity Introduction Dissolving pulp is the raw material for production of regenerated cellulose and cellulose derivatives. The demand on textile fibres, for example, is increasing and the improvement of the quality of dissolving pulps is still a research topic. For example, several pre-treatment of dissolving pulps in order to enhance their properties have been investigated (Kihlman et al. 2011; Li et al. 2012; Ambjörnsson et al. 2014). The various dissolving pulps have common that their processing involves, in most cases, chemical reactions and that their reactivity is one of the most important parameters for quality evaluation. A reactive pulp improves the efficiency of the subsequent process in terms of reaction speed resulting in a more homogeneous and more valuable material, while the con- sumption of chemicals is reduced (Ibarra et al. 2010). The pulp reactivity is a general concept, which is defined as the capacity of a pulp to participate in diverse chemical reactions, i.e. the concept is related to the accessibility of the hydroxyl groups of cellulose to chemical reagents and depends on the structure and morphology of the fibre and on the reaction conditions, among others on the pH (Krassig 1993; Christoffersson et al. 2002; Fischer et al. 2009; Strunk et al. 2011). In the viscose process, which is the main application of dissolving pulp, cellulose dis- solution is governed by its reaction with carbon disulfide (CS 2 ) to form the soluble cellulose xanthate. An alkaline pretreatment is practiced to for fibre swelling, which increases the OH groups’ accessibility and facilitates the xanthate formation. Shortly, good swelling is a prerequi- site to an acceptable reactivity. The assessment of pulp suitability to the viscose process is commonly performed by Fock’s method. It is a simplified reproduction of the viscose production at the laboratory scale (Tian 2013), in the course of which the percentage of solubilized cellulose after reaction with CS 2 is determined. By combining the results of this test with other characteristics, a broad information on the reactiv- ity is obtained; in this context the gamma number, which represents the degree of substitution of cellulose in the cellulose xanthate (Lanieri et al. 2014), and the filter value, which is a quantification of the undissolved par- ticles in the viscose solution (Schleicher and Borrmeister 1998) are relevant. However, these methods are time con- suming and require specific equipments (Christoffersson et al. 2002). Furthermore, concern about CS 2 toxicity limits their application in academic laboratories. In this context, the fibres’ thickness swelling and dissolution ability also attracted attention, which can Brought to you by | University of British Columbia - UBC Authenticated Download Date | 2/23/16 7:07 PM