Improved absorption characteristics of thermally modified beech veneer produced by plasma treatment

Holz als Roh- und Werkstoff (Impact Factor: 1.24). 09/2012; 70(5):545-549. DOI: 10.1007/s00107-011-0581-8


In 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.

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    • "Plasma processes may serve in improving the hydrophobicity and protection of surface materials (Drummond et al. 1997; Magalhães and Souza 2002; Bente et al. 2004) without changing the chemical structure of the bulk. Furthermore , hydrophilicity can also be improved (Avramidis et al. 2012; Tang et al. 2012; Zheng et al. 2012) through introduction of hydroxyl and carbonyl groups on a thin surface layer (Asandulesa et al. 2010). This approach is important for materials with roughened and irregular surfaces, such as MDF, which consequently have a low wettability and poor adhesion properties. "
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    ABSTRACT: The effects of two power levels (50 and 150 W) and five time levels (10, 20, 40, 60 and 120 s) of glow discharge in helium dielectric barrier discharge (He-DBD) has been investigated in the context of surface modification of medium density fiberboard (MDF) panels. He-DBD elevated the surface wettability of MDF panels as assessed by dynamic contact angle (CA) measurements including the determination of surface free energy, droplet volume and spreading contact area of droplets. The chemical changes of the MDF surfaces were also characterized by X-ray photoelectron spectroscopy (XPS). Expectedly, the apparent CA and droplet volume decreased with increasing power and time of glow discharge, mainly at the 150 W power level. The oxygen content of the surfaces, the surface free energy and the spreading contact area increased upon treatment. At higher energy levels the treatment time could be reduced, which is essential for future applications in industrial processes.
    Full-text · Article · Feb 2015 · Holzforschung
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    ABSTRACT: Modification of wood is a method that is used to improve the material properties of wood by altering its chemical nature and in a broader sense it is also a passive process, where changes in properties also occur, but without an alteration of the chemistry of the material. A typical example of passive modification is, for instance, filling of wood cell lumens with resins. Surface modification of wood has the same purpose as the bulk modification, but it is restricted only to treatments of first few layers of wood surface. This review provides an overview of the development of surface modification of wood in the last 10–15 years. This topic has been extensively studied, especially in relation to research and production of wood based composites. However, in the present review the references dealing with modification of lignocellulosic and wood particulates (for instance, wood dust, flakes, and fibres) are in general excluded and the review is focused on surface modification of solid wood and of veneers. Mainly, modification in a narrow sense was considered, i.e. alternating chemical composition of wood building polymers and other compounds in wood. Nevertheless, some less conventional passive surface treatment techniques, for example sol-gel processes, deposition of nanoparticles or mechanical operations have been considered as well. In the first part, an overview of the most common surface modification methods is presented and in the second part the properties that are affected are illustrated through selected publications in literature. It is shown that the topic of surface modification of wood is currently a very viable area of research in wood science and technology. Wood surfaces can be treated by plasmas from various sources; by chemical or enzymatic grafting of functional molecules; coating by application of sol-gel methods, including deposition of nanoparticles; by surface impregnation and with various mechanical operations. The target properties to be improved or even introduced are mostly surface activation for better gluing and adhesion of surface coatings, wettability and resistance to weathering. However, resistance to wood pests, fire retardancy and mechanical properties, especially hardness and abrasion resistance, can also be effectively improved by wood surface modification.
    Full-text · Article · Apr 2013
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    ABSTRACT: Sample material from spruce (Picea abies), beech (Fagus sylvatica) and ash (Fraxinus excelsior) with radial and tangential section was treated by diffuse coplanar surface barrier discharge (DCSBD) plasma generated in air at atmospheric pressure. Plasma activated samples exhibited significantly lower water uptake times of 50 μl droplets and minimal differences in wetting between the two cutting planes (radial and tangential), when compared to the untreated surface. Simultaneously, more uniform spreading of the droplets and increased area of wetting on the activated surface were achieved. The plasma treatment had no effect on the water absorption coefficient of the wood samples. FTIR measurements confirmed the presence of oxygen containing functional groups and structural changes in lignin on the activated wood surface. The minimal heating of the treated samples suggests this method to be applicable to treat heat sensitive wooden materials.
    Full-text · Article · Sep 2013 · Holz als Roh- und Werkstoff
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