Thermal modification kinetics and chemistry of poplar wood in dry and saturated steam media

Abstract

This research work presents a modelling strategy to analyse thermal conversion rates of two thermal wood modification processes based on time-temperature superposition method. It gathers in a single study different original and bibliographic experimental works analysing the dry mass variation that occurs during thermal and hydro-thermal wood modification processes. The mass loss kinetic was successfully modelled using a modified Arrhenius approach. The time-temperature superposition method allowed to define for each wood modification process a master curve and its time shift depending on the treatment temperature. The analysis of ventilated oven and saturated steam treatments pointed out the existence of a continuous single kinetic for the ventilated oven which became more complex for saturated steam since a second kinetic stage appeared. This kinetic difference was sustained by infrared spectra chemical analysis which showed that hemicelluloses degraded much faster in presence of steam while lignin degradation occurred in both conditions.

Moisture Dynamics of Wood-Based Panels and Wood Fibre Insulation Materials

“…WFIB1 is the only insulation material manufactured with hot air, in contrast to the dry manufacturing process of WFIB3, in which a mixture of hot air and steam is used, and the wet manufacturing process of WFIB2, 4 and 5, in which wood fibres have been immersed in water before heating. In hydrothermal treatments, hemicelluloses have been shown to be strongly degraded from the beginning, in contrast to thermal treatments for which the main degradation acts on lignin in the initial stage of thermal degradation ( Marcon et al, 2021 ). Consequently, this higher abundance of cellulose and hemicellulose bonds in WFIB1 as compared to the other wood fibre insulation materials, is likely related to the absence of water in its manufacturing process.…”

The effects of tree age, thickness, and depth of timber on density and mechanical properties of heat-treated black poplar wood (Populus nigra)

“…Decreasing the equilibrium moisture content (EMC) of the wood during heat treatment is another reason for reduced density (Kozakiewicz et al 2019). The main reason for the decrease in moisture content of heat-treated wood at high temperatures is the modification of the wood polymer structure arrangement and the possible softening of lignin (Marcon et al 2021), decrease of wood carbohydrates content as a result of decomposition of a large part of wood cell wall hemicelluloses (Gennari et al 2021), and increase in lignin's proportional content (Abreu et al 2008) that ultimately results in reduction of the wood ability to absorb water and decrease of the equilibrium moisture content of wood (Brito et al 2008).…”

Enhancement of the Weathering Resistance of Heat-Treated Wood: Surface Deposition of Zn Nanoparticles by Electrochemical Activation

“…At high temperatures, heat treatment chemically modifies wood. Chemical changes occur, such as a decrease in the amorphous polysaccharide content, condensation and demethoxylation of lignin, and removal of certain extractives. − Degradation results in a reduction in accessible hydroxyl content and consequently improved dimensional stability and better resistance to degradation by insects and microorganisms . Another positive effect of heat treatment is the attractive darker color.…”