Structure and Properties of All-Cellulose Composites Prepared by Controlling the Dissolution Temperature of a NaOH/Urea Solvent

A novel, easily controllable, and energy saving method, suitable for industrial production of all-cellulose composites (ACCs) from cotton linters, was proposed by solely controlling the dissolution temperature of a sodium hydroxide/urea aqueous solvent. A series of ACCs were prepared from dissolution temperatures of −2, −4, −6, −8, −10, and −12.5 °C. The morphologies of cellulose solutions were observed with an optical microscope. The effects of the dissolution temperature on structures and properties of ACCs were characterized by Fourier transform infrared spectroscopy, optical microscopy, scanning electron microscopy, X-ray diffraction, ultraviolet–visible spectroscopy, thermogravimetric analysis, and tensile tests. The ACCs prepared at −10 °C exhibited the highest mechanical strength among all the ACCs, with a tensile strength and Young's modulus of 108.1 MPa and 4.8 GPa, respectively, much higher than the corresponding values of 51.4 MPa and 3.5 GPa for the pure regenerated cellulose films prepared at −12.5 °C. The ACCs prepared at −10 °C also exhibited better transparency and good thermal stability as a result of the uniform and dense structures.