Chemical changes of steamed timber during short-term photodegradation monitored by FTIR spectroscopy

Abstract

Black locust (Robinia pseudoacacia L.), beech (Fagus sylvatica L.), poplar (Populus x euramericana cv. pannonia) and spruce (Picea abies Karst.) wood samples were treated in saturated steam at 100, 110 and 120 °C for 2 days. Steamed and unsteamed (control) specimens were irradiated using a UV emitter mercury lamp in order to determine the chemical changes generated by UV irradiation. The main goal of the research was to find out if steaming can improve the UV resistance of wood. Chemical changes were determined by diffuse reflectance FTIR spectroscopy. Steaming deacetylated the hemicellulose molecules of hardwood species. Steamed spruce specimens showed the same photodegradation properties as the unsteamed ones. Steaming reduced the photodegradation sensitivity of lignin considerably for black locust only. Steamed hardwood specimens presented greater absorption increase at 1705 cm−1 compared to unsteamed samples, which corresponds to the photodegradation of hemicelluloses.

The behavior of thermally modified wood after exposure in maritime/industrial and urban environments

“…FTIR-ATR spectra were obtained using a PerkinElmer Spectrum Two, equipped with a UATR Two accessory with the diamond crystal at 4 cm −1 resolution and with 8 scans. Baseline correction was made in three points, and after that, spectra were normalized to the maximum band around 1031 cm −1 , using the same method by other authors [ 27 ]. Difference spectra were calculated to compare the modified and unmodified samples, with and without exposition.…”

Discoloration and Surface Changes in Spruce Wood after Accelerated Aging

“…The produced free radicals react with oxygen to form carbonyl groups [34][35][36]. The characteristic peak for guaiacyl lignin (1508 cm −1 ) [37] decreased by approximately 98% of the original absorbance, with a greater decrease observed in the wet mode, where it completely disappeared. A sharp decrease occurred during the first 100 h of irradiation, and further accelerating aging had little effect on lignin changes.…”

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

“…Heat-treated wood is more dimensionally stable; it resists fungal attack, and it does become hydrophobic and less hygroscopic than untreated wood. These transformations are well known and allow for the industrialization and marketing of such a product [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ].…”

“…Previous studies of chemical variation based on FTIR are found in the literature [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ] as well as with other techniques [ 31 , 32 , 33 , 34 ]. Though FTIR is a valid technique, it is not suitable to determine what really happens and what is formed chemically during the hydrophobization reaction of wood.…”