Sorption of water–ethanol mixtures by poplar wood: swelling and viscoelastic behaviour

Abstract

The swelling of wood upon impregnation by aqueous solutions of organic solvents is larger than swelling by pure water. This phenomenon, described as "hyperswelling", results from specific interactions with components of the complex wood microstructure. To understand the combined effect of mixed solvents on wood properties, the specific influence of each solvent on wo od biopolymers and structure must be first characterized. In this study, the effect of th e impregnation of aqueous solutions of ethanol with concentrations from 0 to 100% on the physico-mechanical properties of poplar wood was investigated. For each solution, the sorption behaviour of veneer sapwood samples and the effect of sorption on wood C2MA is member of the European Polysaccharide Network of Excellence (EPNOE), http://www. epnoe .eu.

Synergistic Sorption of Mixed Solvents in Wood Cell Walls: Experimental and Theoretical Approach

“…The cell walls are compact and well bound to the middle lamella, the continuous lignin‐rich phase which connects cell walls through the tissues. On the contrary, in ethanol (Figure C), cell walls swell to a lower extent, in agreement with previous reports . In addition, after saturation with ethanol, primary wall (the cell wall layer nearer to the middle lamella) seems less bounded to the middle lamella, where peeling can be observed, suggesting that intercellular decohesion occurred in ethanol.…”

“…Sorption isotherms of vapor at the equilibrium with water, ethanol and an aqueous ethanol solution are represented in Figure A. The water vapor isotherm, with the sorption of nearly 16% water at p/p° 95, is typical of wood moisture sorption . The shape of the isotherm has often suggested its classification as a type IV IUPAC isotherm, typical of mesoporous solids.…”

“…The water vapor isotherm, with the sorption of nearly 16% water at p/p 95, is typical of wood moisture sorption. [14] The shape of the isotherm has often suggested its classification as a type IV IUPAC isotherm, typical of mesoporous solids. However, the hysteresis loop of condensation in mesopores should have a lower limit at the relative pressure at which capillary tension in the mesopore meniscus exceeds the tensile strength of the condensed liquid.…”

“…Resulting modifications of the physico‐mechanical and hygroscopic properties of lignocellulosic fibers have been monitored by Meier, who reported that ethanol‐water mixtures generate local intercellular decohesion . Studies on other lignocellulosic materials also identified specific effects of the cooperative sorption of water and organics on middle lamellae and different layers of primary and secondary cell walls . In the study of the behavior of (ligno‐)cellulosic fibers in aqueous solutions of NMMO ( N ‐methylmorpholine N ‐oxide), Le Moigne et al observed gradients in swelling and dissolution mechanisms between the different cell walls, related to variations in their biochemical composition .…”

“…[12,13] Studies on other lignocellulosic materials also identified specific effects of the cooperative sorption of water and organics on middle lamellae and different layers of primary and secondary cell walls. [14] In the study of the behavior of (ligno-)cellulosic fibers in aqueous solutions of NMMO (N-methylmorpholine N-oxide), Le Moigne et al observed gradients in swelling and dissolution mechanisms between the different cell walls, related to variations in their biochemical composition. [15,16] Acera Fernández et al and Lefeuvre et al showed that the removal of non-cellulosic components from the cell walls of flax fibers with various aqueous and organic solvents could strongly affect the transverse mechanical properties of the fibers and their composites.…”