1,720,991 research outputs found
The effect of air plasma treatment at atmospheric pressure on thermally modified wood surfaces
No full textThis study tests the hypothesis that thermal modification of wood influences the effectivity of air plasma treatment. Micro-veneers of European beech, Scots pine and Norway spruce were thermally modified at two different temperatures and subsequently plasma-treated for 1 and 3 s. The veneer surfaces were characterized in terms of morphology, wetting behaviour and surface chemistry. No severe changes in the veneer surfaces due to plasma treatment were observed by scanning electron microscopy. Plasma treatment increased surface free energy and wettability by water and urea-formaldehyde adhesive; it was more effective on thermally modified wood than on unmodified wood. X-ray photoelectron spectroscopy revealed a similar distribution of oxygen-containing functional groups on the wood surface after plasma treatment of thermally modified and unmodified beech wood. It is suggested that enhanced wettability through plasma treatment is due to the generation of carboxyl groups within the lignin network, which contribute to the polar part of the surface free energy. The high effectiveness of plasma treatment on thermally modified wood might thus be explained by its high relative proportion of lignin
Sanding vs. plasma treatment of aged wood: A comparison with respect to surface energy
No full textTo compare sanding and plasma treatment by dielectric barrier discharge (DBD) with respect to their effects on wood surface characteristics, beech, oak, spruce, and Oregon pine were investigated. For this purpose, the surface energy of aged. freshly sanded or plasma-treated surfaces was examined by contact angle measurement and Calculation of work of adhesion. For both methods, sanding and plasma treatment, an increase in surface energy caused by a heavily increased polar part was found. Plasma treatment turned out to be superior to sanding. To see whether a combined treatment amplified this effect, it combination of sanding and plasma treatment was also investigated. (C) 2007 Elsevier Ltd. All rights reserved.German Research Foundation (DFG) [VI359/1
Plasma Treatment of Wood-Plastic Composites to Enhance Their Adhesion Properties
No full textIn this study, the adhesion properties of adhesives and paints on wood-plastic composites (WPCs) after plasma treatment at atmospheric pressure and ambient air were investigated. Surface energy determination by means of contact angle measurements according to the Owens-Wendt approach and atomic force microscopy to detect changes in surface topography were carried out. An increase in the polar component of surface energy and an increase in surface roughness after plasma treatment were detected, indicating enhanced bond strength. To confirm these results, bond strength tests were conducted. By tensile bond strength tests, increased adhesion of waterborne, solventborne and oil-based paints on plasma treated surfaces was found. Furthermore, by shear bond strength tests, an increase in bond strength of plasma treated WPCs bonded with poly(vinyl acetate) and polyurethane adhesives was ascertained. (C) Koninklijke Brill NV, Leiden, 2008German Research Foundation (DFG) [VI 359/1-3
Increasing the water uptake of wood veneers through plasma treatment at atmospheric pressure
No full textIn order to provide a database which documents the influence of plasma treatment on water uptake of wood veneers, veneers of 27 wood species underwent immersion tests in untreated and plasma-treated states. Plasma treatment was executed using an air driven dielectric barrier discharge at atmospheric pressure. The results showed that plasma treatment led to significantly improved water uptake for most of the wood species, but some wood species remained unaffected after plasma treatment
Microwave drying of wet processed wood fibre insulating boards
No full textA continuous microwave dryer was used for drying wet processed wood fibre based insulating boards. Drying characteristics and energy consumption were compared with convective drying methods. Microwave drying turned out to be faster and facilitates even economical drying of thick boards
Improved absorption characteristics of thermally modified beech veneer produced by plasma treatment
No full textIn this study the effect of an atmospheric pressure plasma treatment by a dielectric barrier discharge (DBD) on the wettability and absorption characteristics of thermally modified beech veneer is investigated. A common immersion test using water and melamine solution has been conducted and showed improved wettability and liquid uptake after plasma treatment. Determination of the weight percent gain (WPG) confirmed increased melamine content after plasma treatment.Federal Ministry of Economics and Technology (BMWi) [KF 2411802WZ9
Improved DMDHEU uptake of beech veneers after plasma treatment at atmospheric pressure
No full textThis study investigated the effect of a plasma treatment at atmospheric pressure on the absorption characteristics of beech veneers by using a dielectric barrier discharge on the DMDHEU (1,3-dimethylol-4,5-dihydroxyethylene urea). Immersion tests with varying immersion durations showed that plasma treatment significantly accelerated the DMDHEU-solution uptake of the veneers. Additionally, improved bulking characteristics were observed for plasma-treated and DMDHEU-immersed veneers
Morphological changes in plasma-exposed poultry red mites (Dermanyssus gallinae) using high-resolution video camera and optical coherence tomography (OCT)
Full text linkAbstract Dermanyssus gallinae , the poultry red mite (PRM), is a hematophagous temporary ectoparasite that causes serious economic losses and animal health impairment on laying hen farms worldwide. Control is limited by the parasite’s hidden lifestyle, restrictions on the use of chemical acaricides and the development of resistance against certain drug classes. As a result, research was conducted to explore alternative control methods. In recent years, atmospheric pressure plasma has been increasingly reported as an alternative to chemical acaricides for pest control. This physical method has also shown promising against PRM under laboratory conditions. However, the detailed mechanisms of action have not yet been elucidated. In the present study, the effects of cold atmospheric pressure plasma on PRM were investigated using digital videography and optical coherence tomography (OCT), an imaging technique that visualizes the topography of surfaces and internal structures. Digital videography showed that a redistribution of the contents of the intestinal tract and excretory organs (Malpighian tubules) occurred immediately after plasma exposure. The body fluids reached the distal leg segments of PRM and parts of the haemocoel showed whiter and denser clumps, indicating a coagulation of the haemocoel components. OCT showed a loss of the boundaries of the hollow organs in transverse and sagittal sectional images as well as in the three-dimensional image reconstruction. In addition, a dorso-ventral shrinkage of the idiosoma was observed in plasma-exposed mites, which had shrunk to 44.0% of its original height six minutes after plasma exposure
Improved bondability of wax-treated wood following plasma treatment
No full textIn 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
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