Furanic Polymerization Causes the Change, Conservation and Recovery of Thermally-Treated Wood Hydrophobicity before and after Moist Conditions Exposure

The Whilhelmy method of contact angle, wood thermal properties (TG/DTG), infrared spectroscopy, etc. was used to define the hydrophobicity of heat-treated beech and fir wood at increasing temperatures between 120 degrees C and 300 degrees C. By exposure to wet conditions during 1 week, the hydrophobic character obtained by the heat treatment remains constant heat-treated. Heat induced wood hydrophobation, was shown by CP MAS C-13 NMR and MALDI ToF mass spectrometry to be mainly caused by furanic moieties produced from heat-induced hemicelluloses degradation. This is caused by the acid environment generated by the hydrolysis of the hemicelluloses acetyl groups. Furfural polymerizes to linear and branched oligomers and finally to water repellent, insoluble furanic resins. The water repellent, black colored, cross-linked polymerized furanic network is present throughout the heat-treated wood. Wood darkening as well as its water repellency due to increasing proportions of black colored furanic resins increase as a function of the increase with treating temperature, becoming particularly evident in the 200 to 300 degrees C treating temperature range.

Automated summary

The hydrophobicity of heat-treated beech and fir wood at different temperatures (120℃ to 300℃) was defined using the Whilhelmy method, wood thermal properties (TG/DTG), infrared spectroscopy, etc. The hydrophobic character obtained by the heat treatment remains constant even when exposed to wet conditions for 1 week. Heat-induced wood hydrophobation is mainly caused by furanic moieties produced from heat-induced degradation of hemicelluloses, which is triggered by the acid environment generated by the hydrolysis of hemicellulose acetyl groups.