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Heat-induced chemical and color changes of extractive-free Black Locust (Rosinia Pseudoacacia) woodAuthor(s): Yao Chen; Jianmin Gao; Yongming Fan; Mandla A. Tshabalala; Nicole M. Stark
Source: BioResources Volume 7, Number 2, 2236-2248; 2012
Publication Series: Scientific Journal (JRNL)
Station: Forest Products Laboratory
PDF: Download Publication (375.92 KB)
DescriptionTo investigate chemical and color changes of the polymeric constituents of black locust (Robinia pseudoacacia) wood during heat treatment, extractive-free wood flour was conditioned to 30% initial moisture content (MC) and heated for 24 h at 120 °C in either an oxygen or nitrogen atmosphere. The color change was measured using the CIELAB color system. Chemical changes of the wood components were determined by means of solid state cross-polarization/magic angle spinning 13C-nuclear magnetic resonance (CPMAS-13C-NMR), Fourier transform infrared (FTIR), diffuse reflectance UV-Vis (DRUV) spectroscopy, and elemental (CHN) analysis. The results showed that lightness (L*) decreased, while chromaticity indexes (a* and b*) and chroma (C*) increased after heat treatment. There was greater color difference (ΔE*in the samples heated in the presence of oxygen compared to nitrogen. CHN analysis showed an increase in hydrogen and oxygen and a decrease in carbon content. NMR spectra confirmed the cleavage of the ß-O-4 structure in the lignin, resulting in a decrease in etherified lignin units and an increase in phenolic structures. DRUV and FTIR spectra confirmed the formation of extensive conjugated structures, such as unsaturated ketones and quinones due to the cleavage of the lignin units. Formation of quinones can be attributed to heat treatment in the presence of oxygen.
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CitationChen, Yao; Gao, Jianmin; Fan, Yongming; Tshabalala, Mandla A.; Stark, Nicole M. 2012. Heat-induced chemical and color changes of extractive-free black locust (Rosinia pseudoacacia) wood. BioResources. 7(2): 2236-2248.
KeywordsHeat treatment, Wood, Chemical changes, Color: 13C-NMR, FTIR-ATR, DRUV
- The Effect of Heat Treatment on the chemical and color change of Black Locust (Robinia Pseudoacacia) wood flour
- Spectroscopic analysis of the role of extractives on heat-induced discoloration of black locust (Robinia pseudoacacia)
- Classification of chemicals in black locust Robinia pseudoacacia wood and bark
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