Effects of thermal modification on the surface and chemical properties of moso bamboo

Abstract

Fast growth and high mechanical properties are the key commercial value of bamboo used in various applications. However, the high contents of starch and sugar in the bamboo may cause issues of biodegradation. Heat treatment provides the effective method to modify the chemical properties of bamboo. This study here investigated the effects of heat treatment technology on modifying the surface and chemical properties of moso bamboo (Phyllostachys edulis). The bamboo heat treatment was conducted in different conditions; specifically, three treatment media (i.e., air, nitrogen, and linseed oil), four treatment temperatures (i.e., 150, 170, 190, and 210 °C), and three durations (i.e., 1, 2, and 4 h) were explored. The results revealed that the treatment temperature and duration imposed a significant effect on the surface color and contact angle of the bamboo. In other words, higher treatment temperatures induced darker surface colors and larger contact angles, which ensure favorable hydrophobicity of the bamboo. Moreover, by inspecting the microstructure of the bamboo, this study discovered that the bamboo treated at high temperatures were prone to intense damage to its tissue structures, particularly the parenchyma cells. In addition, Fourier-transform infrared (FTIR) spectroscopy was conducted to examine heat-induced changes in the chemical components of the bamboo. The results of the FTIR spectroscopy revealed that the intensity of the characteristic absorption peaks of polysaccharides decreased with increasing treatment temperatures, whereas the intensity of lignin peaks demonstrated an opposite changing trend. Through a quantitative analysis of the chemical components of the treated bamboo, the content of holocelluloses, hemicelluloses, and α-celluloses of the treated bamboo was determined. The analytical results were highly consistent with that of the FTIR spectroscopy.