1998 Fiscal Year Final Research Report Summary
The study on the chemo-rheology of wood under high temperature and high pressure steam
| Project/Area Number |
09460077
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
林産学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
NORIMOTO Misato Kyoto University, Wood Research Institute, Professor, 木質科学研究所, 教授 (20027163)
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| Co-Investigator(Kenkyū-buntansha) |
MOROOKA Toshiro Kyoto University, Wood Research Institute, Associate Professor, 木質科学研究所, 助教授 (00192378)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Steam Treatment / Chemo-rheology / Stress-strain Diagram / Stress Relaxation / Creep / Sugi Wood / Compression / Recovery of Deformation |
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| Research Abstract |
When wood specimen compressed largely in the transverse direction is treated by high temperature steam, the deformation is permanently fixed. The aim of this study is to clarify the mechanism through measurements of rheological properties in the radial compression of sugi (Cryptomeria japonica) wood under high temperature steam condition using a newly developed testing machine. The strain recovery in the stress relaxation measurement decreased with steaming time and reached almost zero within 10min at 200。C.The relationship between the residual stress and strain recovery at the end of measurement could be expressed by a single curve regardless of time and temperature. In creep measurement, the compliance curve for 30min and that with pre-steaming for 30min were well connected at 30min when the structural changes due to the degradation or decomposition of cell wall polymers occurred. However, two curves were not connected at 30min when the structural changes such as the regularity incre
… More
ase in cellulose crystalline lattice spacing, the formation of cross-linkings and hydrophobic cohesive structure in the non-crystalline region of the cell wall occurred. The mechanism of fixation by steaming was different depending on the extent of strain recovery in stress relaxation measurement. From the results of the measurements of chemical analysis, X-ray diffraction, JR absorption, mechanical properties, swelling by pridine as well as measurements of rheological properties, the mechanism of fixation was considered as follows. Almost no chemical changes in the cell wall polymers occurred for the strain recovery larger than 0.93. The reduction of strain recovery was caused by the release of stresses due to the degradation of hemicelluloses for the strain recovery between 0.93 and 0.60. The regularity increase in cellulose crystalline lattice spacing, the formation of cross-linking and hydrophobic cohesive structure in the non-crystalline region of the cell wall resulted in the fixation for the strain recovery between 0.60 and 0.20. The decomposition of lignin as well as hemicelluloses caused perfect fixation for the strain recovery smaller than 0.20. Less
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