1994 Fiscal Year Final Research Report Summary
Histologrcal Changes of Softwood Sufaces During Outdoor Weathering.
| Project/Area Number |
05660183
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
林産学
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| Research Institution | Yokohama National University |
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Principal Investigator |
YATA Shigeki Yokohama National University, Fuculty of Education, Professor, 教育学部, 教授 (30046510)
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| Project Period (FY) |
1993 – 1994
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| Keywords | weathering / histological change / photodegradation / solar spectrum |
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| Research Abstract |
Flat-grained surface of sugi sapwood were weathered behind filters which transmitted selected regions of the ultraviolet and visible spectrum, whether from sample exposed to, or sheltered from rain. Histological changes of surface were studied by light and scanning-electron microscopy. Color of surface was turned from light-yellow to brown by ultraviolet light and visible part of the spectrum less than 500nm during the early part of the exposure period. After darkening, the surface was successively faded by the washing action of rain. The brownish decomposition products were soluble in water. Occurrence of small parallel checks was not caused by the solar irradiation or the rainfall alone but by the interaction of the photodegradation and the drying stress. Lignin was degraded by ultraviolet spectrum for 0.2mm thick from the surface in earlywood. The photodegraded cell in earlywood were collapsed by the surface tension of water. at the evaporating process of liquid water after rainfall. Strength loss of 75% was recorded for the earlywood after 2 months exposure.
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