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Coloring characteristics of in situ lignin during heat treatment |
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| Authors: | Chen Yao Fan Yongming Gao Jianmin Li Houkun |
| Institution: | 1. College of Material Science and Technology, Beijing Forestry University, No. 35, Qinghua Donglu, Haidian District, 100083, Beijing, China 2. Wood Science and Engineering Key Laboratory of Ministry of Education and Key Laboratory of Beijing Education Commission, Beijing Forestry University, 100083, Beijing, China 3. Tsinghua University, Laboratory of Green Chemical Reaction Engineering and Technology, Beijing, China |
| Abstract: | To investigate the effects of lignin on the discoloration of Black locust (Robinia pseudoacacia) wood during heat treatment, chromatic indexes of the extractive-free wood samples are examined at different moisture contents (MC) under oxygen and nitrogen environment, respectively. The organic acids are produced during heat treatment, resulting in pH decrease in the samples. Components absorbing visible light are formed during heat treatment, and oxygen and moisture contents have obvious effects on the decrease in L*, increase in a* value, yellowness (b*) and total color difference (ΔE) of the samples. It is found that the β-5, C α C β unsaturated bond, the conjugated carbonyl group, quinones structures, α, β-unsaturated ketone and α-C?=?O in lignin increased after heat treatment. The formation of condensation products, the low-molecular-weight phenolic substances and the oxidation products in lignin result in the increment of the light absorption within the entire visible region. |
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