Cellulose-rich templates from naturally found and cultivation woods diffused in the South-European area: a comprehensive investigation for novel wood-polymer hybrids

Wood-polymer hybrids demonstrate unique perspectives in green architecture, energy-efficiency building, optoelectronics, photovoltaic devices, and energy storage materials. The fabrication of wood-polymer hybrids preliminary involves the acquisition of delignified wood templates. In this framework, the potentiality of species diffused in the Mediterranean area is nearly unexplored. For such purpose, four hardwoods (Beech, European Hop Hornbeam, Turkey Oak and Paulownia) and one softwood (Corsican Pine) have been selected on the basis of their anatomical features, density, and potential exploitation of natural resources. The goal is to evaluate and compare the properties of delignified woods derived from the selected species for the fabrication of wood-polymer hybrids, including transparent wood products. Wood samples of different cut (longitudinal or transversal) and thickness (1 mm or 3 mm) were soaked in an alkaline sulfite solution and mildly bleached in hydrogen peroxide. Dry mass loss was determined in different experimental conditions. Macro- and microstructure of delignified woods have been investigated by optical microscopy, scanning electron microscopy, infrared spectroscopy and X-ray diffraction analysis. Thermal degradation profiles were acquired by thermogravimetry, the total transmittance measured in the UV-Vis range and mechanical properties evaluated by tensile tests. The dry mass loss ranged within 26-52%. Delignified hardwoods showed enhanced optical transmittance especially Paulownia (+ 80%) and Turkey Oak (+ 140%), characterized by large vessels and thin cell walls, while the macro- and mesostructure along with tensile properties were preserved. These cellulose-rich wood templates deserve to be further considered for the fabrication of wood-polymer hybrids and particularly transparent wood products.