Swelling and Dissolution of Cellulose Part 1: Free Floating Cotton and Wood Fibres in N‐Methylmorpholine‐N‐oxide–Water Mixtures

<jats:title>Abstract</jats:title><jats:p><jats:bold>Summary:</jats:bold> Five modes describing the behaviour of cellulose fibres dipped in a chemical have been identified: <jats:list list-type="simple"> <jats:list-item> <jats:p>Mode 1: Fast dissolution by disintegration into fragments</jats:p> </jats:list-item> <jats:list-item> <jats:p>Mode 2: Large swelling by ballooning, and dissolution</jats:p> </jats:list-item> <jats:list-item> <jats:p>Mode 3: Large swelling by ballooning, and no dissolution</jats:p> </jats:list-item> <jats:list-item> <jats:p>Mode 4: Homogeneous swelling, and no dissolution</jats:p> </jats:list-item> <jats:list-item> <jats:p>Mode 5: No swelling and no dissolution</jats:p> </jats:list-item> </jats:list> In the case of the behaviour of wood and cotton cellulose fibres in <jats:italic>N</jats:italic>‐methylmorpholine‐<jats:italic>N</jats:italic>‐oxide (NMMO) and water mixtures, four domains of water content have been identified. Below 17% of water up to monohydrate (13%), the fibres are disintegrated into rod‐like fragments and dissolve (mode 1). In NMMO – water mixtures containing 19–24% water, the cellulose fibres exhibit a heterogeneous swelling by forming balloons (composed of dissolved cellulose holds inside a membrane) separated with non‐swollen sections. The whole fibre will completely dissolve (mode 2) in four successive steps (growth of the balloons, burst of the balloons, dissolution of the non‐swollen sections and finally dissolution of the membrane). With still greater water contents (25–30%), only the ballooning phenomenon is observed, with a partial dissolution inside the balloon (mode 3). Above 35% of water, the fibres swell homogeneously and are not dissolving (mode 4).</jats:p>