Structure Study of Cellulose Fibers Wet-Spun from Environmentally Friendly NaOH/Urea Aqueous Solutions

• Published in: Biomacromolecules Vol. 8; no. 6; pp. 1918 - 1926
• Main Authors: Chen, Xuming, Burger, Christian, Wan, Fen, Zhang, Jun, Rong, Lixia, Hsiao, Benjamin S, Chu, Benjamin, Cai, Jie, Zhang, Lina
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.06.2007
• Subjects: Applied sciences; AQUEOUS SOLUTIONS; Biopolymers - chemistry; CELLULOSE; Cellulose - chemistry; COTTON; CRYSTAL STRUCTURE; Crystallization; Environment; Exact sciences and technology; FIBERS; Fibers and threads; FLOW RATE; Forms of application and semi-finished materials; HYDRODYNAMICS; Light; LIGHT SCATTERING; MATERIALS SCIENCE; Molecular Conformation; Molecular Weight; national synchrotron light source; ORIENTATION; PARTICLE ACCELERATORS; Polymer industry, paints, wood; POLYMERIZATION; Polymers - chemistry; PRODUCTION; RAYON; SCATTERING; Scattering, Radiation; Sodium Hydroxide - chemistry; Solubility; SOLVENTS; SYNCHROTRON RADIATION; Technology of polymers; Temperature; Urea - chemistry; VISCOSE; Water - chemistry; X-RAY DIFFRACTION; Artificial fiber; Hydrodynamic radius; Crystal orientation; Basic solution; Cellulose hydrate; Radius of gyration; Crystallinity; Experimental study; Wet spinning; Structure processing relationship; Urea; Supramolecular structure; Molecular aggregation; Aqueous solution; Conformation
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm061186i

In this study, structure changes of regenerated cellulose fibers wet-spun from a cotton linter pulp (degree of polymerization ∼620) solution in an NaOH/urea solvent under different conditions were investigated by simultaneous synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). WAXD results indicated that the increase in flow rate during spinning produced a better crystal orientation and a higher degree of crystallinity, whereas a 2-fold increase in draw ratio only affected the crystal orientation. When coagulated in a H2SO4/Na2SO4 aqueous solution at 15 °C, the regenerated fibers exhibited the highest crystallinity and a crystal orientation comparable to that of commercial rayon fibers by the viscose method. SAXS patterns exhibited a pair of meridional maxima in all regenerated cellulose fibers, indicating the existence of a lamellar structure. A fibrillar superstructure was observed only at higher flow rates (>20 m/min). The conformation of cellulose molecules in NaOH/urea aqueous solution was also investigated by static and dynamic light scattering. It was found that cellulose chains formed aggregates with a radius of gyration, R g, of about 232 nm and an apparent hydrodynamic radius, R h, of about 172 nm. The NaOH/urea solvent system is low-cost and environmentally friendly, which may offer an alternative route to replace more hazardous existing methods for the production of regenerated cellulose fibers.