Structure study of cellulose fibers wet-spun from environmentally friendly NaOH/urea aqueous solutions.
In this study, structure changes of regenerated cellulose fibers wet-spun from a cotton linter pulp (degree of polymerization approximately 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 degrees 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, Rg, of about 232 nm and an apparent hydrodynamic radius, Rh, 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.
Chen
Xuming
X
Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA.
Burger
Christian
C
Wan
Fen
F
Zhang
Jun
J
Rong
Lixia
L
Hsiao
Benjamin S
BS
Chu
Benjamin
B
Cai
Jie
J
Zhang
Lina
L
D001704:Biopolymers / Q000737:chemistry; D002482:Cellulose / Q000737:chemistry*; D003460:Crystallization; D004777:Environment; D008027:Light; D008968:Molecular Conformation; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry; D012542:Scattering, Radiation; D012972:Sodium Hydroxide / Q000737:chemistry*; D012995:Solubility; D013696:Temperature; D014508:Urea / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
D001704:Biopolymers; D011108:Polymers; D014867:Water; D012972:Sodium Hydroxide; D014508:Urea; D002482:Cellulose