Wood cellulose films with different foldabilities triggered by dissolution and regeneration from concentrated H2SO4 and NaOH/urea aqueous solutions

Forests are a major source of wealth for Canadians, and cellulose makes up the "skeleton" of wood fibers. Concentrated H2SO4 and NaOH/urea aqueous solutions are two efficient solvents that can rapidly dissolve cellulose. Our preliminary experiment obtained regenerated wood cellulose films with different mechanical properties from these two solvents. Therefore, herein, we aim to investigate the effects of aqueous solvents on the structure and properties of wood cellulose films. Regenerated cellulose (RC) films were produced by dissolving wood cellulose in either 64 wt% H2SO4 solution (RC-H4) or NaOH/urea aqueous solution (RC-N4). RC-H4 showed the higher tensile strength (109.78 +/- 2.14 MPa), better folding endurance (20-28 times), and higher torsion angle (42 degrees) than RC-N4 (62.90 +/- 2.27 MPa, un-foldable, and 12 degrees). The increased cellulose contents in the H2SO4 solutions from 3 to 5 wt% resulted in an improved tensile strength from 102.61 +/- 1.99 to 132.93 +/- 5.64 MPa and did not affect the foldability. RC-H4 also exhibited better water vapor barrier property (1.52 +/- 0.04 x 10(-7) g m(-1) h(-1) Pa-1), superior transparency (similar to 90 % transmittance at 800 nm), but lower thermal stability compared to RC-N4. This work provides special insights into the regenerated wood cellulose from two aqueous solvents and is expected to facilitate the development of high-performance RC films from abundant forestry resources.