Transparent, UV blocking, and strong wood-based biocomposites with isotropic optical and mechanical properties

Transparent wood-based materials show great potential for energy-efficient housing and construction due to their ideal optical performances, good mechanical strengths, and low thermal conductivity. However, it still remains a great challenge to fabricate UV-blocking and strong transparent wood-based materials with isotropic optical and mechanical properties, mainly due to the natural anisotropy of wood. Herein, we describe a facile strategy to prepare transparent wood-based biocomposites by integrating delignified wood particles with poly(vinyl alcohol) (PVA) impregnation prior to the compression treatment. This method enables biocomposites to show desirable isotropic optical and mechanical properties, easily tunable high wood component percentage and UV-blocking ability. The enhanced interfacial bonding between wood particles and PVA polymer, together with a similar refractive index, synergistically contributes to excellent performance. The resulting biocomposites (approximately thickness of 1 mm) possess isotropic optical and UV-blocking properties and have a maximum optical transmittance of 62%. The highest tensile strength and flexural strength can reach 86.8 and 158.8 MPa, respectively. Moreover, they display low thermal conductivity (0.38–0.42 W m−1 k−1) and suitable thermal stability. Therefore, this study provides a new method to optimize the properties of transparent wood-based materials for utilization in energy-saving building fields.