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Study on the Effect of Lignin Removal Rate on the Dielectric Properties of Delignified Materials

by Hui Xu, Fengqi Qiu, Weishuai Han and Zhenhua Xue

Coatings 2024, 14(11), 1421; https://doi.org/10.3390/coatings14111421 - 8 Nov 2024

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To investigate the relationship between the lignin removal rate change of wood and its dielectric properties, this study employed Mongolian Scotch Pine and Paulownia as the test materials. The acidic sodium chlorite method was used to delignify the treated material, and the lignin removal rate was determined at a specified reaction time interval to ascertain the dielectric constant and the tangent of the dielectric loss angle. The findings revealed that: As the delignification process progresses, the lignin content declines, accompanied by a reduction in the dielectric constant at elevated frequencies. This decline reaches a plateau near 10 MHz. The results demonstrated that the dielectric constant of the samples decreased with an increase in frequency and exhibited a stabilizing effect near 10 MHz. However, the dielectric constant of delignified wood was significantly higher than that of untreated wood. Additionally, the dielectric constant exhibited a linear relationship with the increase in lignin removal rate, while the tangent of the dielectric loss angle demonstrated a tendency to increase and then decrease. An investigation into the dielectric properties of delignified wood can yield valuable data and a theoretical foundation for the development of wood-based dielectric materials. Full article

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14 pages, 2837 KiB

Open AccessArticle

Laws Governing Free and Actual Drying Shrinkage of 50 mm Thick Mongolian Scotch Pine Timber

by Xiaodong Zhu, Jingyao Zhao, Wanhui Gao, Cheng Qian, Yunjia Duan, Shuaichao Niu and Yingchun Cai

Forests 2021, 12(11), 1500; https://doi.org/10.3390/f12111500 - 30 Oct 2021

Cited by 7 | Viewed by 2016

Abstract

The relationships between free shrinkage and actual shrinkage of different layers in Mongolian Scotch pine (Pinus sylvestris var. mongolica Litv.) were explored to provide basic data for the further study of drying shrinkage properties. The free shrinkage coefficients at different temperatures and the actual shrinkage strain of each layer were examined under conventional drying. The results showed high precision of free drying shrinkage of corresponding layers of thin small test strips in each layer of sawn timber. The free shrinkage increased linearly as moisture content declined. At the same temperature, the free shrinkage coefficient reached the largest values for the first layer (above 0.267%), while the smallest values were recorded for the ninth layer (below 0.249%). Except for the ninth layer, the free shrinkage coefficients in width directions of other representative layers decreased as temperature increased. At constant temperature, the difference in free shrinkage coefficient of test materials in the length direction of sawn timber was small for the first layer, but slightly larger and changed irregularly in the fifth and ninth layer direction. At the end of conventional drying, the plastic deformation of each layer in the early stage of drying showed a reducing trend or even reversal due to the effects of reverse stress and later damp heat. In sum, these findings look promising for future optimization of wood drying process. Full article

(This article belongs to the Section Wood Science and Forest Products)

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