Changes in vibrational properties of wood can be used to determine changes in the wood cell wall resulting from chemical modification. The dynamic Young's modulus to specific gravity ratio (E'/γ) and internal friction (tan δ) for chemically modified wood compared to those for untreated wood showed major differences in cell-wall modification and lumen filling modification. Increasing the moisture content of the cell wall also has a major effect on the vibrational properties of chemically modified wood. In general, treatments that resulted in lowering the moisture content of the cell wall also lowered internal friction within the cell wall. Vapor phase reactions with formaldehyde had the greatest effect in stabilizing the cell wall against changes in dynamic mechanical properties with increasing moisture content
