ObjectiveMultilayer transparent wood is laminated transparent woods (the same direction or cross direction) under vacuum. This will greatly reduce the anisotropy of transparent wood.
MethodThis study explored the process of making three kinds of tree species with different densities: balsa (0.21 g/cm3), paulownia (0.33 g/cm3) and basswood (0.49 g/cm3), and tested their transmittance and tensile properties. In order to produce a centimeter thick transparent wood, the lamination method was adopted. The mechanical properties and transmission of single layer and multilayer transparent wood with the same thickness were compared.
ResultComparing their similarities and differences, balsa wood has the smallest density and contains more space inside, which is easier to remove lignin and impregnate resin. There were many extractive in paulownia (8.9%), hence it needs to be impregnated in sodium hydroxide (NaOH) to removal extractive and open the blocked pits. The density of basswood was 0.49 g/cm3, which caused lignin difficult to remove, but its tensile property was good. Besides the influence of tree species, the thickness had a great influence on transparent wood. The thicker the wood was, the greater the difficulty of removing lignin was. The properties of transparent wood combined with the same direction were closer to the original transparent wood. However, the transmission of transparent wood combined with the cross direction was lower than original transparent wood. But the difference between transverse and longitudinal stretch had been narrowed.
ConclusionOur study widens the selection of transparent wood species and makes it possible for transparent wood with high thickness and low cost.