Hexamethyldisiloxane-Plasma Coating of Wood Surfaces for Creating Water Repellent Characteristics

Abstract

IntroductionThe plasma state, recognized as the fourth state of matter, is broadly defined as a gaseous environment composed of charged and neutral species with a net zero electric charge. This manifestation of matter can be generated by increasing the energy content of atoms and molecules regardless the nature of the energy source. Consequently plasma can be created by involving caloric, radiant, or mechanical energy sources. Plasma states can be divided in two main categories according to their intrinsic energy content: hot plasmas (or near-equilibrium plasmas) and cold plasmas (nonequilibrium plasmas) often called silent discharges or glow discharges. Hot plasmas are characterized by near thermodynamic equilibrium and very high degrees of ionization, and are composed of neutral and charged molecular and atomic species, and electrons having extremely high energies (e. g., electric arcs, rocket jets, plasmas generated by nuclear reactions). Actually, it is estimated that more than 90 % of the known Universe exists under the plasma state. All active celestial bodies are hot plasma environments. Cold plasmas are composed of low energy atomic and molecular charged and neutral species and of energetic electrons. However, due to the low caloric capacity of the electrons the energy is not distributed to the reactor walls and consequently, these plasmas operate at reactor temperatures comparable to room temperature. These plasmas are also characterized by very low degrees of ionization. Consequently, these plasmas are suitable for the modification of organic substrates.Besides natural plasmas like the ionosphere, lightning, the rarefied interplanetary-space-plasma, man-made plasmas can be initiated by increasing the energy content of a gaseous system. Plasmas are loosing energy toward the walls which confine them by collision and radiation, and consequently energy must be supplied in a continuous manner to sustain the plasma state. The easiest way to meet this requirement is by using electrical energy; and this is the reason why the most common plasmas are electrical discharges.An electrical discharge (e. g. cold plasma) is initiated when omnipresent free electrons (due to cosmic radiation) of a low-pressure gaseous environment are accelerated to kinetic energy levels capable of inducing ionization and fragmentation processes. The newly resulted electrons will also be accelerated leading to further elastic and inelastic collisions and to the generation of the plasma state.It is noteworthy that the energy levels of the cold plasma species (1-10 eV; predominantly 0.5-3 eV) are comparable to the chemical bond energies, and consequently this state represents a novel and very significant way for modifying the structure of volatile organic and inorganic matter. The plasma species can also interact with solid-phase substances generating chemical and morphological changes in the very top layers of the plasma-exposed substrates. These features make electrical discharges an excellent tool for generating unconventional reaction m...

Pretreatments of natural fibers and their application as reinforcing material in polymer composites—A review

“…Additionally, a nodular structure was also noted in oxygen-plasma treated pulps [146]. Furthermore, the hexamethyldisiloxane-plasma was studied on pine wood surfaces [147]. Evidence from X-ray photoelectron spectroscopy, infrared spectroscopy and atomic force microscopy indicated that a siloxane plasma polymer was deposited upon the surface.…”

Surface wettability of Brazilian tropical wood flooring treated with He plasma

“…The effect of plasma on wettability of these materials is generated mainly by changes in their chemical structure and surface cleaning process (Dineff et al 2011), which occur only in the outermost layer of the material's surface (Denes et al 1999). These chemical changes, and consequently the increase of hydrophilicity, occur by the introduction of new functional groups on the substrate surface and/or by breaking the polymer chains on the outermost layer followed by crosslinking (Liston 1989;Carlotti and Mas 1998;D'agostino et al 2008).…”

Weathering Performance of Wood Coated with a Combination of Alkoxysilanes and Rutile TiO2 Heirarchical Nanostructures

“…These include nanosol treatment (Mahltig et al 2008;Xu et al 2010;Tshabalala et al 2011), the plasma-enhanced chemical vapor deposition of thin barrier films onto the wood surface (Denes et al 1999), and hydro/solvothermal treatment (Li et al 2010). Recently, there has been a renewed interest in the use of titanium dioxide nanostructures in combination with surface-active organic compounds to enhance the UV resistance and water repellence properties of wood surfaces (Wang et al 2011;Chu et al 2014;Wang et al 2014).…”