This report examines the effects of thermal modification on the mechanical properties of soft wood, at the cell wall level, to clarify how micro-level behavior (cellulose) relates with macro-level behavior (bulk wood). Both level behaviors were simultaneously measured in thermally modified 5-mm-thick specimens containing annual rings under tensile loading, using synchrotron radiation XRD. Thermal modifications were performed under six sets of conditions: 2 temperature × 3 mass loss (ML). Maximum strain, maximum load, stiffness, and strain energy were obtained at both levels based on corresponding load–strain curves. Data showed that thermal modification tended to reduce the mechanical performance of both, with two exceptions: maximum cellulose strain was increased when wood had been modified at 150 °C, and cellulose stiffness was increased when wood had been modified at 180 °C (except for the ML-18% condition). The extent of those reductions differed between bulk wood and cellulose. The mechanical behavior modified at 150 °C suggested that properties of bulk wood are also influenced by binding elements that connect cellulose microfibrils with the surrounding matrix. When expressed in terms of cellulose-to-bulk (C/B) ratios, different properties were likewise affected by temperature and ML. The tendencies exhibited by C/B ratios of maximum strain and strain energy differed greatly by modification temperature. The C/B ratios of maximum load and stiffness showed similar trends with increasing ML under both temperature conditions although those changes differed in magnitude. Moreover, it seems that not only ML, but also the thermal modification speed, can affect the mechanical behavior of the cellulose microfibrils.
This is a preview of subscription content, log in to check access.
Buy single article
Instant unlimited access to the full article PDF.
Price includes VAT for USA
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
This is the net price. Taxes to be calculated in checkout.
Bekhta P, Niemz P (2003) Effect of high temperature on the change in color, dimensional stability and mechanical properties of spruce wood. Holzforschung 57:539–546
Tjeerdsma BF, Boonstra M, Pizzi A, Tekely P, Militz H (1998) Characterisation of thermally modified wood: molecular reasons for wood performance improvement. Holz Roh- Werkstoff 56:149–153
Mitchell PH (1988) Irreversible property changes of small loblolly pine specimens heated in air, nitrogen, or oxygen. Wood Fiber Sci 20(3):320–355
Koceafe D, Poncsak S, Tang JJ, Bouazara M (2010) Effect of heat on the mechanical properties of North American jack pine: thermogravimetric study. J Mater Sci 45:681–687. https://doi.org/10.1007/s10853-006-0054-3
Borrega M, Kärenlampi PP (2008) Mechanical behavior of heat-treated spruce (Picea abies) wood at constant moisture content and ambient humidity. Holz Roh Werkst 66:63–69
Endo K, Obataya E, Zeniya N, Matsuo M (2016) Effects of heating humidity on the physical properties of hydrothermally treated spruce wood. Wood Sci Technol 50:1161–1179
Yildiz S, Gezer ED, Yildiz UC (2005) Mechanical and chemical behavior of spruce wood modified by heat. Build Environ 41:1762–1766
Sobue N, Hirai N, Asano I (1971) On the measurement of strain distribution in wood under the axial tension force by X-ray diffraction. Zairyo 20:1188–1193
Nakai T, Yamamoto H, Nakao T (2005) The relationship between macroscopic strain and crystal lattice strain in wood under uniaxial stress in the fiber direction. J Wood Sci 51:193–194
Nakai T, Yamamoto H, Nakao T, Hamatake M (2006) Mechanical behavior of the crystal lattice of natural cellulose in wood under repeated uniaxial tension stress in the fiber wood. Wood Sci Technol 40:683–695
Peura M, Grotkopp I, Lemke H, Vikkula A, Laine J, Müller M, Serimaa R (2006) Negative poisson ratio crystalline cellulose in kraft cooked Norway spruce. Biomacromolecules 7:1521–1528
Peura M, Kölln K, Grotkopp I, Saranpää P, Müller M, Serimaa R (2007) The effect of axial strain on crystalline cellulose in Norway spruce. Wood Sci Technol 41:565–583
Montero C, Clair B, Alméras T, Lee A, Gril J (2012) Relationship between wood elastic strain under bending and cellulose crystal strain. Compos Sci Technol 72:175–181
Lee CG, Yamasaki M, Kojima E, Sugimoto T, Sasaki Y (2019) Synchrotron X-ray measurements of cellulose in wood cell wall layers of Pinus densiflora in the transmission and reflectance modes. Part 2: results with axial loading, (in contribution) Holzforschung
Bhuiyan MTR, Hirai N, Sobue N (2000) Change of crystallinity in wood cellulose by heat treatment under dried and moist conditions. J Wood Sci 46:431–436
Bhuiyan MTR, Hirai N, Sobue N (2001) Effect if intermittent heat treatment on crystallinity in wood cellulose. J Wood Sci 47:336–341
Abe K, Yamamoto H (2005) Mechanical interaction between cellulose microfibril and matrix substance in wood cell determined by X-ray diffraction. J Wood Sci 51:334–338
Lee CG, Yamasaki M, Sugimoto T, Sasaki Y (2019) Synchrotron X-ray measurement of cellulose in wood cell wall layers of Pinus densiflora in the transmission and reflectance modes. Part 1: results without loading. Holzforschung 73(7):613–619
Cave ID (1966) Theory of X-ray measurement of microfibril angle in wood. Forest Prod J 16:37–42
Meylan BA (1967) Measurement of microfibril angle by X-ray diffraction. For Prod J 17:51–58
Matsuo M, Yokoyama M, Umemura K, Sugiyama J, Kawai S, Gril J, Kubodera S, Mitsutani T, Ozaki H, Sakamoto M, Imamura M (2011) Aging of wood: analysis of color changes during natural aging and heat treatment. Holzforschung 65:361–368
We are grateful to Dr. Miyuki Matsuo-Ueda for helpful idea for thermally modified wood. This work was supported in part by the Photon-Beam Platform Project of the Ministry of Education, Culture, Sports, Science and Technology. The XRD experiments were conducted at the BL8S1 of Aichi Synchrotron Radiation Center, Aichi Science & Technology Foundation, Aichi, Japan (Approval No. 2016G1012). This work was supported by Grant-in-Aid for Scientific Research (C) Number 17K06638.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Kojima, E., Yamasaki, M., Imaeda, K. et al. Effects of thermal modification on the mechanical properties of the wood cell wall of soft wood: behavior of S2 cellulose microfibrils under tensile loading. J Mater Sci (2020) doi:10.1007/s10853-020-04346-7