Comparative study of moisture absorption and dimensional stability of Chinese cedar wood with conventional drying and superheated steam drying

Abstract

ABSTRACTThe effects of drying methods on equilibrated moisture content (MC) and swelling efficiency of Chinese cedar (Cryptomeria fortunei) wood were studied in this paper. Drying experiments were conducted with conventional (CON) drying and superheated steam (SHS) drying under atmospheric pressure. Specimens were equilibrated at two environment conditions to measure moisture and dimensional changes, and then the moisture excluding efficiency (MEE) and antiswelling efficiency (ASE) were determined. Results showed that the equilibrated MC of artificial-dried wood was lower than control samples (air drying), and the equilibrated MC of wood with SHS drying was lower than that with CON drying, which indicated that MEE was enhanced in SHS drying process. Similar results were found in swelling efficiency and ASE of artificial-dried wood and the control. The mechanism was studied by dynamic mechanical analysis (DMA) and X-ray diffraction analysis (XRD). The DMA results showed that both of relative storage modulus and relative loss modulus were the highest for SHS-dried wood and the lowest for the control samples. As for the crystalline structure assessed by changes of XRD, the results showed that the cellulose crystallinity and crystallite size of Chinese cedar wood with SHS drying were the highest, and control specimens were the lowest. All the analyses showed that Chinese cedar wood with low hygroscopic and high dimensional stability could be gotten through SHS drying process.