Investigation of beech wood modified by radio-frequency discharge plasma (original) (raw)
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Study of wood surface pre-treatment by radio-frequency discharge plasma
2019
An investigation was made of wood of the species oak (Quercus petraea), beech (Fagus sylvatica L.), maple (Acer pseudoplatanus) and ash (Fraxinus excelsior) pre-treated using radio-frequency (RF) plasma in air at reduced pressure. Physical and chemical changes for all of the wood species were determined using measurements of water contact angles and FTIR-ATR spectroscopy. The results confirmed an increase in the wood’s hydrophilicity/polarity in all cases, caused by an increase in –OH group concentration due to irradiation by RF plasma. The content of oxygen-containing functional groups after treatment by RF plasma significantly increased, and the water contact angles were diminished. FTIR-ATR spectroscopy confirmed that RF plasma modification of the surfaces of all investigated wood samples led to certain changes, which were also dependent on the time of plasma exposure.
Modification of Wood by Atmospheric Discharge Plasma
2011
The atmospheric discharge plasma has been used to improve the wetting and adhesion properties of wood. The low-temperature plasma processes are attractive for wood industry applications because of their lower cost, and ability to operate in-line without vacuum systems. However, using the sessile droplet technique, we have identified a significant increase of polar component of surface free energy. Polar part of surface free energy is associated with the presence of acid/base forces (electron donor–acceptor bonds). The treatment of wood exhibited a substantial aging effect; nevertheless the treated surface never recovers to its initial hydrophobic state. The enhancement of wood wettability is a necessary condition to promote a better adhesion with a water-based adhesives and coatings, which is currently being studied.
Modification of wood by low-temperature atmospheric discharge plasma
Modification of wood by low-temperature atmospheric discharge plasma. Discharge plasma at atmospheric pressure was used to improve the wetting and adhesion properties of wood. Although also lowpressure plasma processes and namely atmospheric pressure processes are more attractive for wood industry applications because of their lower cost, higher throughput, and ability to operate in-line without vacuum systems. Atmospheric pressure plasma system is typically based on volume diffuse barrier discharge arrangement, where the treated material is placed between the discharge electrodes. However, using the sessile droplet technique, we have identified a significant increase of polar component of surface free energy. Polar part of surface free energy is associated with the presence of acid/base forces (electron donor-acceptor bonds). The treatment of wood exhibited a substantial aging effect; nevertheless the treated surface never recovers to its initial hydrophobic state. The enhancement of wood wettability is a necessary condition to promote a better adhesion with a water-based adhesives and coatings, which is currently being studied. The involvement of planar plasma source in our case makes the quality of the plasma treatment completely independent on the thickness and electrical conductivity of the wood material treated.
Pre-treatment of beech wood by cold plasma
Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology, 2013
Pre-treatment of beech wood by cold plasma. Adhesive joints of wood could be strengthened by plasma treatment of the surface. The low-temperature discharge plasma has been used to improve the wetting and adhesion properties of wood. The contact angle of water drop showed a steep decrease after activation by RF plasma in air and the surface energy and its polar component of beech wood were increased with time of plasma activation.
Plasma Chemistry and Plasma Processing, 2010
Surface inactivation is a phenomenon that causes poor adhesion. A wood surface exposed to contaminants such as dust or atmospheric grime can experience surface inactivation. Inactivation mechanisms can reduce the attractive forces on the wood surface and lead to a decrease in wettability. Plasma treatment has been applied to recover inactivated wood surfaces for better adhesion and bonding. Plasma treatment technology is very simple and the cost is rather low. In addition, this treatment produces no environmental pollution. In this study, low pressure plasma treatment was applied to reactivate the surfaces of spruce wood for glue bonding and to increase wettability after a 9-year period of natural surface inactivation. Changes in contact angles, surface energy, surface colour and bonding strength of inactivated and oxygen plasma treated wood surfaces were studied. Wettability, bonding and other mechanical strength properties of plywood panels increased with the oxygen plasma treatment.
Holzforschung, 2020
Plasma treatment is becoming a mature technique for modification of surfaces of various materials, including wood. A better insight in the treatment process and the impact of the plasma on properties of wood bulk are still needed. The study was performed on Norway spruce and common beech wood, as well as their thermally modified variations. The formations of the airborne discharge, as well as mass changes of the treated wood, were monitored. The impact of such treatment on wood-coating interaction was investigated by evaluating the dynamic wettability and penetration into wood. At the wood surface, plasma streamers were observed more intense on denser latewood regions. Wood mass loss was higher with increasing number of passes through the plasma discharge and was lower for thermally modified wood than for unmodified wood. Plasma treatment increased the surface free energy of all wood species and lowered the contact angles of a waterborne coating, these together indicating enhanced wettability after treatment. Finally, the distribution and penetration depth of the coating were studied with X-ray microtomography. It was found that the coating penetrated deeper into beech than into spruce wood. However, the treatment with plasma increased the penetration of the coating only into spruce wood.
The wood products industry is going through hard times in both Canada and the US. It is faced with competition from emerging economies and substitution products. The North American economy is slowing down with decreasing demand for wood products. Under these conditions, the industry should be innovative and develop the next generation of wood products. Plasma technology could be used to improve wood surface properties and compensate for the variations to be expected from an organic living material, which is sensitive to its environment (moisture, water, temperature, ultraviolet light). In recent years, the plastic and textile industries have begun experimenting with plasma technology to activate surfaces, mainly to improve coating/substrate adhesion. The literature on potential applications of plasma treatment to wood surfaces is very limited. This report describes the results of an exploratory study on the effect of plasma treatments on sugar maple wood using different gases and mixtures (N 2 , H 2 , O 2 , and Ar) at different pressures (13.3 -665 Pa). Water wettability and adhesion between surface and waterborne polyurethane acrylate coatings were also studied. The results show that it was possible, under certain conditions, to significantly increase wood/coating adhesion by 30 -100%. This improvement is correlated with improvements in wood surface energy and coating penetration depth. In addition, chemical analyses showed that, with some plasma types, the treatment led to new atoms being grafted.
Impact of RF and DC Plasma on Wood Structure
Romanian Reports in Physics
The effect of DC reflex and RF plasma is observed on three types of wood samples: beech, oak and spruce. The aim is to perform surface hydrophilization and hydrophobization and characterize the modifications occurring at the surface of the wood. FTIR-ATR measurements were performed to characterize and identify the chemical bonds on the surface of the treated samples.
Improved bondability of wax-treated wood following plasma treatment
Wood Science and Technology, 2010
In this study, the impact of a plasma treatment using dielectric barrier discharge at atmospheric pressure on wax-treated beech was investigated by surface energy determination and adhesion tests. Measurements of the surface energy revealed a strong increase in surface polarity along with increased surface energy as a result of the plasma treatment, pointing to increased adhesion properties. To evaluate the adhesion properties of a polyvinyl acetate (PVAc) adhesive on beech treated with montan ester wax and synthetic Fischer-Tropsch wax, a special peel test was applied. This peel test provided evidence of increased adhesion of the PVAc after plasma treatment of both materials investigated.