Response relationship between color and chemical composition and microstructure of heat- treated wood

Abstract

The magnitude of the color change of heat-treated wood is closely related to the chemical composition of the wood, and the change in chemical composition is the essential reason for changes in the mechanical properties of heat-treated wood. Exploring the influence and linear correlation of the magnitude of the lightness indicator (L*) of poplar (Populus tomentosa Carr.) and spruce (Picea asperata Mast.) in heat treatment on the chemical composition and cell wall structure of heat-treated wood, and constructing a response relationship between L* values and them. The relative content of cellulose in heat-treated poplar increased gradually and was significantly negatively correlated with the L* value, however, the heat-treated spruce first increased and then decreased, and the correlation with the L* value was insignificant. The L* value of the heat-treated wood was significant positively correlated with the content of hemicellulose and lignin. The CrI and crystalline size of poplar and spruce after thermal modification first increased and then decreased with the decrease of L* value, and the L* values had a superior response relationship with their crystallite size. The shrinkage deformation and radial cracking of the cells of poplar and spruce after thermal modification became increasingly obvious as the L* value gradually decreased, the L* values had an extremely significant positive correlation with their radial thickness of the cell wall. Therefore, the constructed response relationship provides a theoretical basis for accurate and nondestructive testing of the mechanical properties of heat-treated wood using color parameters as a rapid detection indicator.