Mechanics, optics, and thermodynamics of water transport in chemically modified transparent wood composites

Effects of chemical modification on mechanical, optical, and water transport behavior of transparent wood composites (TWCs1) were investigated. TWCs were produced from a methacrylate resin and balsa wood templates using two delignifying pretreatments, namely lignin-oxidation and lignin-modification, and three interfacial modifications, namely acetylation, methacrylation, and treatment with 2-hydroxyethyl methacrylate. Water transport behavior was investigated via immersion at three temperatures, where diffusion coefficients, kinetic rate constants, and activation energies of water diffusion were obtained. Lignin-modified TWCs were generally more water resistant than lignin-oxidized TWCs. Interfacial modification of the wood template via acetylation and methacrylation were observed to further decrease diffusion coefficients and increase activation energies of diffusion compared to unmodified TWCs, indicating superior fiber-matrix compatibility and improved moisture resistance relative to other tested TWCs. Flexural properties of post-dried TWCs were not adversely affected by moisture compared to samples unconditioned by water. TWC optical properties were measured in pre-immersion, water-saturated, and post-dried states to characterize deterioration of transmittance and haze. While moisture saturation degraded optical properties, optical performance of select TWC classes were observed to rebound upon drying.