Anti-microbial cationic wood nanofiber films exhibiting high visible light transparency and UV-blocking ability together with good mechanical and oxygen barrier properties were produced directly from sawdust.

In this work, deep eutectic solvent (DES) based on imidazole and triethylmethylammonium chloride was used as a reaction medium for the esterification of cellulose nanofiber (CNF) and all-cellulose composite (ACC) films with n-octylsuccinic anhydride (OSA) to obtain high strength and sustainable films with increased hydrophobicity. Diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy were used to prove the success of the modification. The mechanical strength of the modified films was analyzed in dry, humid, and wet conditions, and the hydrophobicity of the films was indicated in terms of contact angle measurements. In addition, water absorption and transparency of the films were characterized. The modification was proven to be simple and fast, and mild conditions of 80 °C reaction temperature and 1 h reaction time were used. DES/OSA- modified CNF film exhibited better mechanical properties in dry, humid, and wet conditions compared to reference CNF film, and DES/OSA-modified ACC film displayed notable higher mechanical properties in wet state compared to that of reference CNF film (31 MPa tensile strength and 6.1% strain at break vs. 18 MPa and 2.2%, respectively). These improvements were partly attributed to higher contact angles of modified films (ACC-DES/OSA 60° and CNF-DES/OSA 51°) compared to CNF film (37°). Graphic abstract

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Tissue paper softness relies on two major factors, the bulk softness, which can be indicated by the elasticity of the sheet, and surface softness. Measurement of surface softness is complicated and often requires a multi-step process. A key parameter defining surface softness is the topography of the surface, particularly the crepe structure and its periodicity. Herein, we present a novel approach to measure and quantify the tissue paper surface crepe structure and periodicity based on the detection of waviness along the sample using laser scanning confocal microscopy (LSM) and X-ray tomography (XRT). In addition, field emission scanning electron microscope (FESEM) was used to characterize the tissue paper surface. We demonstrate that surface topography is directly correlated to the erosion of the doctor blade, which is used to remove the dry tissue paper from the Yankee cylinder. Because of its accuracy and simplicity, the laser confocal microscopy method has the potential to be used directly on the production line to monitor the production process of the tissue paper. XRT revealed more structural details of the tissue paper structure in 3D, and it allowed for the reconstruction of the surface and the internal structure of the tissue paper. Graphic abstract