Effects of quenching on relaxation properties of wet wood

Abstract

A new relaxation property is discussed on the basis of creep behavior of wet wood specimens pretreated with heating at various temperatures followed by quenching. The treated samples showed more marked relaxation than that of an untreated sample. The relationship between relaxation time and heating history was represented by an equation ln(λ) = −(γα _f − k ₁)ΔT + [ln(λ _g) + k ₂], where ln(λ) is the logarithmic relaxation time of wet samples after quenching, ΔT is the difference between the heating temperature and the glass transition temperature (T _g), ln(λ _g) is the logarithmic relaxation time at T _g, γ is a constant, α _f is the coefficient of thermal bulk expansion, and k ₁ and k ₂ are constants. It was concluded from the analysis of experimental results that the change in the relaxation property caused by heating and the following quenching is due to the temporary free volume created by freezing of molecular chain motion of wood components, most probably lignin, during quenching.