Plasma Surface Treatment of Polypropylene Reinforcing Fibres by Dielectric Barrier Discharge

This article deals with plasma treatment of polypropylene fibres used as concrete admixtures for improving its mechanical properties. Plasma treatment was conducted in low-temperature plasma at atmospheric pressure. Dielectric barrier discharges in both coplanar and volume configuration of electrodes were used for this purpose. The degree of hydrophilicity caused by plasma treatment was determined by measuring the rate of penetration of liquids into the porous media, so called Washburn method. The optimized plasma treatment of industrially used polypropylene fibres ensured further 20% surface wettability improvement comparing to the standard chemical treatment.Tento článek se věnuje plazmové úpravě polypropylénových vláken, které se používají jako příměs do betonu pro zlepšení jeho mechanických vlastností. Plazmová úprava byla provedena v nízkoteplotní plazmě za atmosférického tlaku. Za tímto účelem byly použity dielektrické bariérové výboje s koplanární i objemovou konfigurací elektrod. Míra hydrofility způsobená plazmovou úpravou byla stanovena měřením rychlosti nasákání kvapalin do porézního prostředí, tzv. Washburnova metoda. Optimalizovaná plazmová úprava průmyslově používaných polypropylénových vláken zabezpečila zvýšení smáčenlivosti o dalších 20% v porovnání s vláknami se standartní chemickou úpravou

Mass Production of Plasma Activated Water: Case Studies of Its Biocidal Effect on Algae and Cyanobacteria

Efficient treatment of contaminated water in industrially viable volumes is still a challenging task. The hydrodynamic cavitation plasma jet (HCPJ) is a promising plasma source for industrial-scale generation of biologically active environments at high flow rates of several m(3)/h. The combined effect of a hydro-mechanical phenomenon consisting of hydrodynamic cavitation and electrical discharge in cavitation voids was found to be highly efficient for large-volume generation of reactive oxygen species, ultraviolet (UV) radiation, and electro-mechanical stress in a liquid environment. Here, the persistence of biocidal properties of HCPJ-activated water (i.e., plasma-activated water (PAW)) was tested by the study of algae and cyanobacteria inactivation. Algae and cyanobacteria cultivated in media containing PAW (1:1) were completely inactivated after 72 h from first exposure. The test was performed at a total power input of up to 0.5 kWh/m(3) at the treated liquid flow rate of 1 m(3)/h. A beneficial modification of our previous HCPJ design is described and thoroughly characterized with respect to the changes of hydrodynamic flow conditions as well as discharge performance and its optical characteristics. The modification proved to provide high biocidal activity of the resulting PAW, which confirms a strong potential for further design optimization of this promising water (liquid) plasma source

Properties of Plywood Panels Composed of Thermally Densified and Non-Densified Alder and Birch Veneers

Ukrainian companies mainly use birch in the manufacture of plywood, but species, such as black alder, are not yet widely used in the manufacture of plywood due to their poorer properties. It is well known that thermal compression is often used to improve the properties of solid wood. Good lay-up schemes of veneer can maximize the advantages and minimize the disadvantages of these wood species, and generally improve the utility value of the plywood. This research aimed to develop plywood panels with two wood species and two types of veneer treatments in order to evaluate the influences of different lay-up schemes on the properties of the plywood. Five-layer plywood panels were formed with 16 different lay-up schemes using birch (Betula verrucosa Ehrh.) (B) and black alder (Alnus glutinosa L.) (A) veneers, which were non-densified (N) and thermally densified (D). The different lay-up schemes were used to identify opportunities to improve the mechanical and physical properties of the plywood by replacing the birch veneer in the plywood structure with an alternative alder veneer. The veneer sheets were thermally densified in a laboratory hot press at a temperature of 180 °C and pressure of 2 MPa for 3 min. The conducted study showed that the bending strength, modulus of elasticity and shear strength of mixed-species plywood (BD–AN–AN–AN–BD) increased by up to 31.5%, 34.4% and 16.8%, respectively, in comparison to those properties of alder plywood from non-densified veneer (AN–AN–AN–AN–AN), by positioning alder non-densified veneers in the core layers and birch densified veneers in the outer layers. Moreover, the surface roughness of plywood panels with outer layers of birch veneer was lower than that of panels with outer layers of alder veneer. It was shown that non-treated alder veneer, despite exhibiting somewhat lower strength properties than birch veneer, could be successfully used with proper lay-up schemes in the veneer-based products industry

Fast Surface Hydrophilization via Atmospheric Pressure Plasma Polymerization for Biological and Technical Applications

Polymeric surfaces can benefit from functional modifications prior to using them for biological and/or technical applications. Surfaces considered for biocompatibility studies can be modified to gain beneficiary hydrophilic properties. For such modifications, the preparation of highly hydrophilic surfaces by means of plasma polymerization can be a good alternative to classical wet chemistry or plasma activation in simple atomic or molecular gasses. Atmospheric pressure plasma polymerization makes possible rapid, simple, and time-stable hydrophilic surface preparation, regardless of the type and properties of the material whose surface is to be modified. In this work, the surface of polypropylene was coated with a thin nanolayer of plasma-polymer which was prepared from a low-concentration mixture of propane-butane in nitrogen using atmospheric pressure plasma. A deposition time of only 1 second was necessary to achieve satisfactory hydrophilic properties. Highly hydrophilic, stable surfaces were obtained when the deposition time was 10 seconds. The thin layers of the prepared plasma-polymer exhibit highly stable wetting properties, they are smooth, homogeneous, flexible, and have good adhesion to the surface of polypropylene substrates. Moreover, they are constituted from essential elements only (C, H, N, O). This makes the presented modified plasma-polymer surfaces interesting for further studies in biological and/or technical applications

Odstranění Microcystis Aeruginosa kombinovaným působením plazmového výboje a hydrodynamické kavitace

Cyanobacterial water blooms represent toxicological, ecological and technological problems around the globe. When present in raw water used for drinking water production, one of the best strategies is to remove the cyanobacterial biomass gently before treatment, avoiding cell destruction and cyanotoxins release. This paper presents a new method for the removal of cyanobacterial biomass during drinking water pre-treatment that combines hydrodynamic cavitation with cold plasma discharge. Cavitation produces press stress that causes Microcystis gas vesicles to collapse. The cyanobacteria then sink, allowing for removal by sedimentation. The cyanobacteria showed no signs of revitalisation, even after seven days under optimal conditions with nutrient enrichment, as photosynthetic activity is negatively affected by hydrogen peroxide produced by plasma burnt in the cavitation cloud. Using this method, cyanobacteria can be removed in a single treatment, with no increase in microcystin concentration. This novel technology appears to be highly promising for continual treatment of raw water inflow in drinking water treatment plants and will also be of interest to those wishing to treat surface waters without the use of algaecide

Selective Cu electroplating enabled by surface patterning and enhanced conductivity of carbon fiber reinforced polymers upon air plasma etching

We demonstrate a sustainable post-processing of carbon fiber reinforced epoxy polymer (CFRP) composites by air plasma etching that permits regular electroconductive surface patterning through direct Cu galvanic metallization, in contrast to the untreated composite. Our study reveals a significant property dependence of the composite with respect to the position to the fiber/matrix composite surface and treatment. The enhancement in electrical conductivity was not compromised by the lower structural integrity of the composite, as the embedded carbon fibers remained unaffected by the air plasma etching process. The metallized Cu domains on the composite exhibit good hardness and excellent solderability potential. Thus, the electroconductive surface patterning of the composite, preceding galvanic metallization, facilitates the selective deposition of Cu layer domains. This step by step process, relying on the creation of selective electroconductive areas on the composite by plasma etching, enables galvanic metallization. Consequently, it enhances the potential for multifunctional composite applications. The feasibility of galvanic metallization brings new perspectives in selective metallization of composites by allowing the tailoring of the metal layer thickness, microstructure and selection of the metal