Impact of thermal modification combined with silicon compounds treatment on wood structure

In the present study silicon containing formulations were investigated for their applicability in solid wood modification. Black pine sapwood was thermally modified at 180oC and 200oC (3, 5 and 7 hours) and afterwards, an additional chemical treatment with silicon containing systems (N-2-aminoethyl-3-aminopropyltrimethoxysilane) followed, in an attempt to invigorate hydrophobicity and durability of wood. Infrared spectroscopy (FTIR) was used to examine the formation of new bonds in the treated materials and atomic absorption spectrometry (AAS) to measure the silane concentration. The results showed a high reactivity between thermally modified wood and organosilicon compounds. The presence of bands representing vibrations of the Si–O–CH3 group in IR spectra of modified wood and after extraction confirms the stable character of the formed bonds between the hydroxyl group of wood and the methoxy groups of organosilanes. Furthermore, reactivity between wood and AE-APTMOS and alkyd resin solution was confirmed by the AAS results. Alkyd resin caused a higher concentration of silica in wood mass, which increases as the thermal treatment temperature increases. The organosilicon compounds caused a much higher resistance to water washout, revealing permanent binding of silanes to wood mass.

Changes in physical-mechanical properties and chemical compositions of Toona sinensis wood before and after thermal treatment

Vacuum heat treatment was used to improve the dimensional stability of Toona sinensis wood in this study, the shrinking and swelling rates, the physical-mechanical properties, and the chemical compositions before and after the thermal treatment were evaluated. The results revealed that the volume shrinkage and swelling rate for the heat-treated wood samples were decreased by 45.60% and 49.95%, respectively at 220°C for 6 h indicating that thermal treatment could obviously improve the dimensional stability of Toona sinensis wood. Thermal treatment also decreased the mechanical strength. The surface color was changed by the treatment. The chemical composition results showed the decrease in density and mechanical strength was due to the partial degradation of hemicellulose during the treatment. The results of this study that vacuum heat treatment could improve the dimensional stability by sacrificing somewhat mechanical strength, the treatment conditions mainly the temperature should be properly controlled to archive an optimized improvement in dimensional stability with minimum reduction in mechanical strength.

Effect of thermal and retarding treatment on flammability rate of tropical tree species

Wood is integral to the construction industry despite the fact that it is a highly flammable material. Due to thermal stress, it is subject to the process of pyrolysis. However, not every type of wood burns the same. This dissimilarity is caused by the changes in its internal structure. Flammability rate of tree species can be modified by means of thermal modification, i.e. change in its internal structure or by using coating compositions which form a fire-protecting layer on its surface. The paper comprises a testing and an evaluation of iroko wood which is predominantly used as floor covering and cladding material for building structures. The authors focus on determining the connection between the structure of this exotic tree type and the eventual thermal degradation (burning course, significant changes, amount of material burnt, etc.) of the samples. Small size samples were used during laboratory measurements. Their width and thickness were approximately the same as for commonly used cladding boards. The data obtained in the laboratory have been processed, transformed into evaluation criteria and connected with theoretical knowledge, creating an overview of its eventual flammability. Laboratory test results prove low flammability rate of test samples. Mass loss was an important criterion. Thermal treatment, which changes the internal structure and thus improves its properties (T group; test samples), had no significant effect on the eventual flammability. On the other hand, the flammability rate of samples was better when using a fire retardant (R and TR group; test samples), because the retardant lowers the flammability by more than half.

Changes in gross calorific value of thermally treated scots pine (Pinus Sylvestris L.) and sessile oak (Quercus Petraea L.) wood and their explanation using ftir spectroscopy

Scots pine (Pinus sylvestris L.) and Sessile oak (Quercus petraea L.) wood were thermally treated in an oven at the temperatures of 160°C, and 200°C under atmospheric pressure in the presence of air for 3 and 9 hrs. The mass loss and gross calorific value were determined. Non-treated wood samples achieved a gross calorific value of 22 193 J.g-1 for pine wood and 19 277 J.g-1 for oak wood. Whereas the calorific value of pine wood with increasing severity of treatment decreased, in the case of oak it increased. The mass loss increased with increasing treatment severity by both wood species. Mentioned differences in pine and oak wood behaviour using ATR-FTIR spectroscopy were explained. In the case of pine wood with increasing temperature and time of exposure a decrease of resin acids was observed. This may be contributed to decrease in GCV. In the case of oak wood, mainly at temperature of 200°C the degradation of hemicelluloses was observed that results in relative increasing in the lignin content with followed increase in the GCV.