Changes of wood cell walls in response to hygro-mechanical steam treatment

Guo, Juan; Song, Kunlin; Salmén, Lennart; Yin, Yafang

doi:10.1016/j.carbpol.2014.08.040

Cited by 112 publications

(59 citation statements)

References 45 publications

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“…For the CS treated EW, S 180,50 , the T g decreased to 76°C, which is ca 17% lower than that for S untr . At the same time, the modulus of the wood increased in accordance with the indentation modulus increment after CS treatment (Guo et al 2015). The modulus increase is probably a result of the densification occurring under the compressive condition as well as a higher cellulose crystallinity and more perfectly arranged cellulose crystals after CS treatment (Navi and Sandberg 2011;Guo et al 2016).…”

Section: Resultsmentioning

confidence: 59%

“…The quantitative composition, the supramolecular architecture (the arrangement of the constituents) affect wood properties, especially under changing T, MC and mechanical actions. During THM treatment, densification under compressive conditions and the degradation and rearrangement of hemicelluloses, lignin and cellulose are the main parameters for the improvement of wood properties (Ito et al 1998;Heger 2004;Diouf et al 2011;Guo et al 2015;Yin et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin

et al. 2017

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For producing wood products without fractures based on thermo-hygro-mechanical (THM) treatments, it is essential to understand how steaming and compression change the wood softening and cell wall components. In this paper, the effects of compression combined with steam treatment (CS) on the viscoelasticity of the in-situ lignin of Chinese fir has been investigated through dynamic mechanical analysis (DMA) under fully saturated conditions. Several variations were studied, such as the softening temperature (T g ) and apparent activation energy (ΔH a ) of the softening process in response to CS treatment conditions (such as steam temperature and compression ratio) under separate consideration of earlywood (EW) and latewood (LW). No difference between EW and LW with respect to the viscoelasticity was noted. T g and ΔH a of the lignin softening were nearly unaffected by the compression ratio, but were highly influenced by the steam temperature. The T g decreased significantly with CS treatments at or above 160 o C, but showed no appreciable change, compared to the native wood, at the lower steaming temperature of 140 o C. ΔH a increased at higher steam temperatures, while ΔH a showed a decreasing tendency with decreasing T g . This indicates that lignin undergoes a simultaneous depolymerization as well as a condensation during CS treatment.

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Section: Resultsmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin

et al. 2017

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“…4. An investigation of the structure of micropores and mesopores in modified wood, such as steam treatment (Yin et al 2011b), hygro-mechanical treatment (Guo et al 2015), fire retardant, decay resistance. The results would promote an understanding of the effects and mechanism of modified wood, while also providing a scientific basis for the development of environmentally compatible wood products.…”

Section: Resultsmentioning

confidence: 99%

Comparison of changes in micropores and mesopores in the wood cell walls of sapwood and heartwood

Yin

Song

et al. 2015

Wood Sci Technol

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The objective of this paper was to investigate size distribution of micropores and mesopores within the wood cell walls between sapwood and heartwood by using nitrogen adsorption method and to find out implications for the biological durability and further processing such as in drying and preservation treatment. The pore shape, specific surface area and pore size distribution of Chinese fir (Cunninghamia lanceolata) were evaluated using the hysteresis loops, Brunauer-Emmett-Teller (BET) and density functional theories, respectively. Both the sapwood and heartwood exhibited slit-shaped pores with regard to the H3 type of hysteresis loop of the isotherm. However, more mesopores were found in the sapwood, while the micropores increased with a decrease in mesopores in the heartwood. Furthermore, the earlywood and latewood in the sapwood had a higher BET-specific surface area (2.088 and 1.255 m 2 g -1 , respectively) compared with the earlywood (1.058 m 2 g -1 ) and latewood (0.787 m 2 g -1 ) in the heartwood. This could be caused by an increase in depositions in the extractive that partly filled the mesopores of the heartwood cell walls during the transformation from the sapwood. Additionally, a larger amount of mesopores existed in the earlywood in comparison with the latewood in the sapwood. However, there was no significant difference in the amounts of the micropores and mesopores, when comparing the earlywood with the latewood in the heartwood.

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“…A promising THM technique is Compression combined with Steam (CS) treatment, as compressing wood in the transverse direction under the steaming environment allows to densify wood samples without fractures. Anatomical, structural, chemical, micromechanical and hygroscopic properties of wood under CS treatment have been intensely investigated (Inoue et al 1993;Ito et al 1998;Navi and Girardet 2000;Navi and Heger 2004;Yin et al 2011;Guo et al 2015). However, the response mechanism of wood cell walls to CS treatment has not been fully understood, due to the rather complicated chemical and structural changes in the wood cell wall upon the steaming and compression treatment.…”

Section: Introductionmentioning

confidence: 98%

The influence of thermo-hygro-mechanical treatment on the micro- and nanoscale architecture of wood cell walls using small- and wide-angle X-ray scattering

et al. 2016

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Tracking the changes of cellulose crystallites upon thermo-hygro-mechanical treatment is essential to understand the response of wood cell walls to steam and compression. In this paper the influence of Compression combined with Steam (CS) treatment on wood cellulose crystallites and pores structure of Chinese fir (Cunninghamia lanceolata) was studied under different steaming temperatures and compression ratios. Small-angle X-ray scattering and wide-angle X-ray scattering were used to investigate the changes of cellulose crystallites dimension, aspect ratio, fibril diameter distribution, non-crystalline fraction, the number of chains in each microfibril, as well as the fractal dimension and size of pores in response to CS treatment conditions. Results indicate that the crystallinity increased due to CS treatment, but did not show alteration with varying CS treatment conditions, i.e. seemed nearly unaffected by higher temperatures or compression ratio, both for earlywood and latewood. The cellulose crystallite diameter depended on processing parameters: it increased with increasing treatment temperature. No considerable differences were found for earlywood and latewood. We interpret our findings as a rearrangement of adjacent cellulose chains towards higher crystalline perfection attributing to the increase in crystallinity. The same effect allows a larger coherence length of crystalline order and therefore features an increasing cross-sectional dimension. In general we can state that the CS treatment leads to higher crystallinity and more perfectly arranged cellulose crystals, while it does not greatly affect the microfibril diameter but rather the amorphous regions of the microfibrils and the surrounding hemicellulose and lignin.

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Changes of wood cell walls in response to hygro-mechanical steam treatment

Cited by 112 publications

References 45 publications

Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin

Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin

Comparison of changes in micropores and mesopores in the wood cell walls of sapwood and heartwood

The influence of thermo-hygro-mechanical treatment on the micro- and nanoscale architecture of wood cell walls using small- and wide-angle X-ray scattering

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