Abstract
Thermal modification (TM) is an ecological and low-cost pretreated method to improve the dimensional stability and decay resistance of wood. This study systematically investigates the relevance between the evolution of chemical structure and the physical and mechanical properties during wood thermal modification processes. Moreover, the volatility of compounds (VOCs) was analyzed using a thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TGA-FTIR) and a pyrolizer coupled with gas chromatography/mass spectrometer (Py-GC/MS). With an increase of TM temperature, the anti-shrink efficiency and contact angle increased, while the equilibrium moisture content decreased. This result indicates that the dimensional stability improved markedly due to the reduction of hydrophilic hydroxyl (–OH). However, a slight decrease of the moduli of elasticity and of rupture was observed after TM due to the thermal degradation of hemicellulose and cellulose. Based on a TGA-FTIR analysis, the small molecular gaseous components were composed of H2O, CH4, CO2, and CO, where H2O was the dominant component with the highest absorbance intensity, i.e., 0.008 at 200 °C. Based on the Py-GC/MS analysis, the VOCs were shown to be mainly composed of acids, aldehydes, ketones, phenols, furans, alcohols, sugars, and esters, where acids were the dominant compounds, with a relative content of 37.05−42.77%.
Highlights
Regarded as a renewable natural composite material, wood has been widely used to produce construction materials, flooring, furniture, and interior finishing materials because of its versatile properties, e.g., favorable strength-to-weight ratio, ease of shaping with tools, as well as beautiful grain and color [1,2]
The results showed that higher temperatures and longer durations led to an increase of mass loss (ML), ranging between 10.78% and 19.10%
The reduction of H and O strongly supports the conclusion that a series of dihydroxylation dihydroxylation (−OH) reactions occurred during the Thermal modification (TM) process, resulting in an increase in
Summary
Regarded as a renewable natural composite material, wood has been widely used to produce construction materials, flooring, furniture, and interior finishing materials because of its versatile properties, e.g., favorable strength-to-weight ratio, ease of shaping with tools, as well as beautiful grain and color [1,2]. Py-GC/MS was developed for the further qualitative and quantitative real-time analysis of each organic component in the volatiles, providing the advantages of rapid analyses, high sensitivity, and effective identification of complex organic compounds released from the wood thermal modification processes [30,31]. Until now, these two instruments have been extensively employed to analyze the components of pyrolysis volatiles of different lignocellulosic biomasses [29,32,33], or their three pseudo components, cellulose [34], hemicellulose [35,36], and lignin [26,31,37]. The release characteristics of VOCs was online of 19 detected by TGA-FTIR and Py-GC/MS
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