Moisture Conent changes in outer and inner part
Fast change at wood surface
Retarded change in inner part
Parameters affecting moisture content changes
Material
Surface treatments
Cross-sectional-area
Swelling and Shrinkage of Wood
From dry state to 7% moisture content: little swelling
7%-FSP: pronounced swelling
Above: no swelling
Impact of moisture content on density
Swelling and Shrinkage Formula
Differential vs. Coefficient of swelling/shrinkage
Differential: Swelling in % at 1% MC changing
Coefficient: Swelling in % at 1% RH change
How big is the difference between radial and tangential shrinkage?
2 times bigger in tangential
tangential > radial > longitudinal
Factors on the degree of swelling and shrinkage
Density
Chemical composition of cellulose
Swelling and Shrinkage Anisotropy - Reasons
Fiber orientation
MFA
Influence of MFA
Shrinkage higher in longitudinal for compression wood
Higher in radial and tangential for normal wood
the higher MFa the higher Swelling/shrinkage in longitudinal direction —> lower in tangential direction
Influence of Density on Anisotropy
Inner vs outer part MC
Inner part: fast change
Outer part: retarded change —> never in quilibrium
Last changeda year ago
