Cellulose Products from Solutions: Film, Fibres and Aerogels

International audienceIt belongs to one of the oldest experiences of mankind to use fibrous materials of plant or animal origin with different fibre lengths and fineness as basic materials of human clothes. Cellulose forms linear macromolecules, preferentially useful for an application as textile fibres. Common used pulp fibres are too short for those applications and have to be transformed into staple fibres like wool or endless fibres like silk by means of solution shaping procedures. Dissolution of cellulose in common protic solvents like water or alcohol is hindered due to intra- and intermolecular hydrogen bonds. For that reason cellulose derivatives like cellulose nitrate, cellulose xanthogenate or cellulose acetate were used first in order to manufacture cellulose man-made fibres. Situation changes after investigation of direct dissolving liquids like cyclic amine oxides, especially N-methylmorpholine-N-oxide, and large-scale manufacturing of it became reality. In the late 1970s up to the late 1990s, direct dissolution technology, nowadays well known as Lyocell process, was developed up to technical scales. Dry-wet shaping has recently developed to a powerful tool for manufacturing of fibres, films, nonwoven or other shapes based on cellulose. The Lyocell process also offers new opportunities for chemical or physical functionalisation of cellulose shapes. Because of technological difficulties caused by the thermal and chemical sensitivity of the NMMO monohydrate and the strong fibrillation behaviour of dry-wet shaped fibres, alternatives are to be found to overcome these problems. CELSOL® and BIOCELSOL® processes are two approaches which investigated for substitution of Lyocell process. Native pulp fibres have to be pretreated before they could be used for direct dissolution in aqueous NaOH, the common solvent of CELSOL and BIOCELSOL processes. Development on direct dissolution in caustic soda is still under investigation and scaled up into semi-technical and technical scales. Besides fibres and films, the manufacture of highly porous materials is a very active field, offering the possibility to use them in a wide range of applications, from biomedical and cosmetics to insulation and electrochemistry. A review of the different processes able to manufacture fibres, films and porous objects is given here