Moisture induced plasticity of amorphous cellulose films from ionic liquid

Amorphous cellulose films were created by regeneration from 1-Ethyl-3-methylimidazolium acetate (EmimAc) solutions. Their mechanical properties were analyzed as a function of water content. Cellulose with different molecular weights, i.e. microcrystalline cellulose (Avicel), Spruce cellulose and bacterial nanocellulose (BNC), were used for film preparation. All the regenerated films were free from EmimAc residues as shown by Fourier transform infrared spectroscopy (FTIR), amorphous as shown by wide angle X-ray spectroscopy (WAXS) and optical transparent. The equilibrium water content (w/w) was measured at different relative humidities. The plasticizing effect of water on the films was evidenced by both tensile tests and dynamical mechanical analysis (DMA) with humidity scans. The mechanical properties were clearly related to the proportional water uptake of the films. The sample with the longest cellulose chains, i.e. BNC, showed significantly larger elongation to brake at high moisture content which was owed to chain entanglements. (C) 2013 Elsevier Ltd. All rights reserved

Effect of xylan content on mechanical properties in regenerated cellulose/xylan blend films from ionic liquid

We report of cellulose and arabinoglucuronoxylan (AGX) blend films made from wood polymers extracted from one and the same tree. Blends were prepared by dissolution of wood polymers in 1-ethyl-3-methylimidazolium acetate (EmimAc). Films were produced by casting EmimAc solution followed by coagulation in ethanol. The films were optically transparent, fully amorphous as shown by wide angle X-ray scattering, and free from EmimAc residues as shown by Fourier transform infrared spectroscopy. Mechanical properties were analyzed as a function of water content. The plasticizing effect of water on the films was evidenced by both tensile and dynamical mechanical analysis measurements with humidity scans. Equilibrium moisture content (w/w) was measured at different relative humidities and the proportional water uptake was clearly related to the mechanical properties. We found good mechanical properties independent of the polysaccharide composition and an increased Young\u27s modulus at low humidities with a maximum at approximately 20 % AGX content. The strengthening effect was removed after leaching the AGX from the films This study shows potential applications of biopolymer extracted from trees as future packaging

Biomimetic Inks Based on Cellulose Nanofibrils and Cross-Linkable Xylans for 3D Printing

This paper presents a sustainable all-wood-based ink which can be used for 3D printing of constructs for a large variety of applications such as clothes, furniture, electronics, and health care products with a customized design and versatile gel properties. The 3D printing technologies where the material is dispensed in the form of liquids, so called inks, have proven suitable for 3D printing dispersions of cellulose nanofibrils (CNFs) because of their unique shear thinning properties. In this study, novel inks were developed with a biomimetic approach where the structural properties of cellulose and the cross-linking function of hemicelluloses that are found in the plant cell wall were utilized. The CNF was mixed with xylan, a hemicellulose extracted from spruce, to introduce cross-linking properties which are essential for the final stability of the printed ink. For xylan to be cross-linkable, it was functionalized with tyramine at different degrees. Evaluation of different ink compositions by rheology measurements and 3D printing tests showed that the degree of tyramine substitution and the ratio of CNFs to xylan-tyramine in the prepared inks influenced the printability and cross-linking density. Both two-layered gridded structures and more complex 3D constructs were printed. Similarly to conventional composites, the interactions between the components and their miscibility are important for the stability of the printed and cross-linked ink. Thus, the influence of tyramine on the adsorption of xylan to cellulose was studied with a quartz crystal microbalance to verify that the functionalization had little influence on xylan\u27s adsorption to cellulose. Utilizing xylan-tyramine in the CNF dispersions resulted in all-wood-based inks which after 3D printing can be cross-linked to form freestanding gels while at the same time, the excellent printing properties of CNFs remain intact