Asghar Tarmian

Due to the use of heat-treated wood products like ThermoWood®, even for indoor applications, the type and amount of volatile organic compounds (VOCs) emitted from the products are essential for indoor air quality and human health. The drying method of wood applied as the first step in the ThermoWood® production process may influence this property. In this study, the effects of radiofrequency/vacuum (RF/V) drying technology in comparison with conventional kiln drying at a mild and normal temperature on the emission of VOCs from Scots pine ThermoWood® were investigated using Headspace Gas Chromatography-Mass spectrometry (HS-GC-MS) and olfactory system (electronic nose). An olfactory machine consisting of 6 metal oxide semiconductors (MOS) sensors were used for this purpose. Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were applied to classify and analyze the data of olfactory signals. Results showed that emission of VOCs was higher in the samples dried by RF/V technology and was mainly consisted of terpenes, aldehydes, and alcohols. Acids were identified as the main VOCs in the ThermoWood® produced from RF/V dried wood. The emission of some VOCs, such as terpenes, was reduced after thermal modification. Overall, it can be concluded that the type and the amount of VOCs of ThermoWood® are influenced by the drying method of wood applied before starting the thermal modification.

Wood disks are very susceptible to checking during drying. The present study was aimed to determine a suitable transducer mounting configuration to detect the drying checks with acoustic emission (AE) technique. AE generated during drying of 30-mm-thick beech (Fagus orientalis L.) wood disk with a diameter of 300 mm were monitored using piezoelectric AE transducers operating at frequency of 50-200 kHz. The transducers were directly attached on the disks with four combinations depending on the sensor number and grain direction. Total number of AE events and event rate were associated with drying time and checking features. The successive formation of near-bark radial checks was detected due to fluctuations in the AE event rate. Results showed that if the transducers are attached to the disk lateral surfaces, the formation of pith checks cannot be detected in the early stages of the check formation. The V-shaped cracks can be only detected when the transducer is mounted very close to the crack location. Overall, our results showed that more than two transducers are required to detect all types of checks occurred during drying of wood disks of this size. They should be attached parallel to the grain, one near to the pith and the rest at a suitable distance around periphery of the disk.

One strategy for improving the treatability of refractory wood species is biological incising, and its efficiency depends on how the microorganisms modify the porous structure of the wood. Evaluation of the bioincised wood treatability...

In this study, the effects of two transparent UV curing coatings (i.e. epoxy acrylate and urethane acrylate) modified by zero, 0.2, and 0.5 loading percent of zinc oxide nanoparticles (ZN) on the weathering resistance of thermally modified timber were investigated. Both coatings improved the weathering resistance of the modified wood; however, epoxy acrylate showed much better performance compared to urethane acrylate. ATR-FTIR results showed no considerable oxidation or chain scission in the epoxy acrylate-coated specimens after six months of weathering, while significant chemical changes occurred in the urethane acrylate-coated specimens. The addition of the nanoparticles reduced the discoloration of both coatings; however, the contact angle and roughness were not significantly affected. Results also showed that the adhesion strength was reduced for both coatings as a result of weathering with the urethane acrylate coating having a lower adhesion strength than the epoxy acrylate. The addition of the ZN, particularly at the higher content, reduced the adhesion strength of the urethane acrylate coating. Generally, the method of fast and simple UV-cured coating of epoxy acrylate alone or coupled with zinc oxide nanoparticles was found to be effective for the protection of thermally modified timber against weathering in outdoor applications.

In this research, we used Pistacia atlantica gum during cooling phase of oil-heat treatment of poplar wood (Populus deltoids) to improve its resistance to the white-rot fungus Trametes versicolor and growth of the mold fungus Penicillium expansum. Thermal modification was carried out using rapeseed oil at 180 degrees C, 200 degrees C and 220 degrees C for 2 hours and 4 hours. The modified wood specimens were then directly cooled in the oil containing 0 %, 5 % and 10 % (w/w) of the gum at 25 degrees C for 30 minutes. The chemical constituents of the essential oil extracted with a Clevenger type apparatus were determined by chromatography-mass spectrometry (GC-MS). The amounts of alpha-pinene, beta-pinene and alpha-terpinolene of the essential oil were 60,2 %, 8,7 % and 3,9 %, respectively. The mold resistance was greatly improved, while the improvement against the decay fungus was only observed for the specimens modified at 180 degrees C. Our results confirmed that the enhanced fungal resistance was not only due to the presence of monoterpenes in the essential oil, but also to a further reduction in the hygroscopicity of the treated wood.