Dielectric barrier discharge treatments at atmospheric pressure for wood surface modification

In this research, the effect of dielectric barrier discharge on mechanically manufactured (sawn, planed or polished) wood surfaces is investigated. The experiments have shown that the best hydrophilia is obtained with a cold plasma discharge in air under atmospheric pressure. Other gases such as helium, nitrogen, and argon have been tested, too. Changes of the wood surface properties were determined by absorption of water and contact angle measurements. As a result of a 1 to 20 seconds long exposure to plasma, wood surfaces became hydrophilic. The absorption of water in wood can be changed up to 22 times higher after plasma treatment in air for 20 seconds duration. The fracture strength of glued wood has been increased by 68% after this plasma pretreatment. Using plasma treatment in methane or acetylene wood surfaces are changed to hydrophobic properties. After plasma treatment for 1 min. in a Ar:CH₄=80:20 gas mixture under atmospheric pressure, the absorption of water in wood is 32 times lower than without plasma treatment. As mentioned before, plasma treatment can produce hydrophobic and hydrophilic wood surfaces. But a good homogeneity of the gas discharge is necessary for the plasma treatment of wood. Zusammenfassung Im Rahmen dieser Arbeit werden die Auswirkungen der dielektrisch behinderten Entladung bei Atmosphärendruck auf mechanisch bearbeitete Holzoberflächen (gesägt, gehobelt oder geschliffen) untersucht. Die Experimente haben gezeigt, dass die höchste Hydrophilität bei einem in Luftatmosphäre gezündetem Plasma erreicht wird. Es werden auch andere Gase verwendet, wie z.B. Helium, Stickstoff und Argon. Zur Untersuchung der veränderten mechanischen und energetischen Eigenschaften der Holzoberflächen werden der Tropfen-Versuch und die Kontaktwinkelmessung verwendet. Durch eine 1 bis 20 Sekunden lange Plasmabehandlung können die Oberflächen hydrophil gestaltet werden. So kann die Eindringzeit von Wasser um Faktor 22 gesteigert werden durch eine 20 Sekunden lange Plasmabehandlung in Umgebungsluft. Die Bruchfestigkeit von Leimholz wird durch die gleiche Plasmavorbehandlung um 68% gesteigert. Werden als Plasmabehandlungsgas Methan oder Acetylen eingesetzt, so wird die Holzoberfläche hydrophob. Durch eine 60 Sekunden lange Plasmabehandlung in einem Ar:CH₄=80:20 Gasgemisch bei Atmosphärendruck wird die Eindringszeit von Wasser um den Faktor 32 gesenkt. Mit Hilfe der Plasmabehandlung können also sowohl hydrophobe als auch hydrophile Holzoberflächen erzeugt werden. Jedoch wird für die Plasmabehandlung von Holz eine sehr homogene Gasentladung benötigt.     

Increasing the water uptake of wood veneers through plasma treatment at atmospheric pressure

In 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.     

Investigation of the plasma effects on wood after activation by diffuse coplanar surface barrier discharge

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.     

Wood surface modification in dielectric barrier discharges at atmospheric pressure for creating water repellent characteristics

This paper is on the development of an effective method to hydrophobize wood surfaces of any kind with the help of gas discharges (plasma). Special gases are injected into a so-called dielectric barrier gas discharge creating thin water-proof layers. One special feature of the dielectric barrier discharge is that it works under atmospheric pressure conditions. This can be realized by isolating the electrodes by a dielectric like quartz glass. With the help of this dielectric, which provides the required conditions for creating thin and even layers through homogenisation of the discharge, a special setup (Ionized-Jet-Generator) was developed. The Ionized-Jet-Generator is a light and robust hand-held unit which works under atmospheric pressure conditions. Therefore, it provides an uncomplicated and cheap way to treat surfaces and can be applied to all shapes of wood.     

低温等离子体亲水改性聚丙烯熔喷非织造布

利用常压介质阻挡放电（APDBD）和低压辉光放电（LPGD）等离子体分别对聚丙烯（PP）非织造布进行亲水改性。分析了气体种类、压强、放电频率、电压、处理时间以及非织造布物理结构等因素对亲水改性的影响规律。采用傅里叶变换－表面衰减全反射红外光谱（FTIR-ATR）表征材料表层化学结构的变化,选用吸水率和吸水速率评价样品的亲水性。结果表明：氧气等离子体能够比氩气等离子体更有效地提高非织造布的吸水率和吸水速率;增大放电频率和电压以及适当延长处理时间,均可显著提高材料的亲水改性效果;样品的比表面积越大, 体积密度越小,材料的吸水能力越高。     

Eco‐friendly plasma treatment of linen‐containing fabrics

In the present work, linen‐containing fabrics were treated with atmospheric pressure plasmas of oxygen, air and nitrogen, and the impact of plasma treatment conditions on the surface chemistry and topography was evaluated. Plasma treatment is accompanied by a remarkable improvement in the hydrophilic properties: creation of new functional groups along with a noticeable increase in the affinity of treated substrates for subsequent H₂O₂‐bleaching. The extent of improvement in wettability as well as subsequent bleachability is governed by both the plasma gas, i.e. oxygen > air > nitrogen > none, and the discharge power, i.e. the higher the power supply, the shorter and greater was the modification extent. Oxygen or air plasma treatment significantly upgrades the hydrophilicity, enhances the subsequent bleachability, saves time, water and energy as well as prevents or decreases pollution at the source, i.e. an eco‐friendly substitute for conventional scouring of linen‐based textiles.     

滑动弧放电等离子体处理对冷鲜猪肉保鲜的影响

为了探索滑动弧放电等离子体对冷鲜猪肉的贮藏保鲜效果,研究空气、氮气、氩气滑动弧放电等离子体对猪肉品质和卫生水平的处理效果,包括感官评价、红度、菌落总数、挥发性盐基氮等品质指标.结果表明:不同放电气体处理均提高了猪肉的感官评价值和红度值.菌落总数和挥发性盐基氮测试表明滑动弧放电处理可延长猪肉的贮藏期,其中氩气处理效果最好...     

Effect of heat treatment on the wettability of white ash and soft maple by water

Heat treatment of wood has attracted a lot of attention both in Europe and recently in North America as an environmentally-friendly wood-protection method. The untreated wood is hydrophilic (high affinity for water). During the heat treatment, wood becomes more and more hydrophobic (low affinity for water) with increasing heat treatment temperature. As a result, it becomes more resistant to biological attacks. Furthermore, it becomes dimensionally more stable compared to untreated wood. Its hardness increases. As the wood becomes more hydrophobic, its wettability by water decreases. The effect of heat treatment is different for each species. Studying the wetting characteristics of heat treated wood gives a good indication of the heat treatment effects on certain wood properties which are related to its degree of hydrophobic character. The aim of this work was to study the characteristics of dynamic wetting process for two different heat-treated North American wood species white ash (Fraxinus americana) and soft maple (Acer rubrum). Contact angle measurements before and after heat treatment showed a significant increase in wood hydrophobicity. Advancing contact angles of a water drop were in all cases higher for heat-treated wood than for untreated wood.     

环境湿度对常压等离子体处理拒水纤维效果的影响

针对常压等离子体处理过程中水分存在的问题,在空气相对湿度分别为5％、65％和95％时,对超高模量聚乙烯进行常压等离子体处理,测定处理前后纤维的静态接触角以及纤维与树脂间的层间剪切强度,采用原子力显微镜和X射线光电子能谱探测纤维表面的变化.结果表明,处理后纤维表面粗糙度、含氧基团和纤维与树脂间的层间剪切强度增加,静态接触...     

Cold plasma hydrophilization of soy protein isolate and milk protein concentrate enables manufacturing of surfactant-free water suspensions. Part I: Hydrophilization of food powders using cold plasma

In this study, we found that treatment with cold plasma influenced the wetting properties of soy protein isolate and milk protein concentrate powders. Cold plasma treatment significantly decreased the apparent contact angle of the powders, indicating hydrophilization of the powders. Cold radiofrequency low-pressure plasma treatment had a larger effect on powder wettability than corona atmospheric plasma discharge. In addition, cold plasma treatment had a more noticeable effect on the wettability of the hydrophobic milk protein concentrate than on the inherently hydrophilic soy protein isolate. Both the soy protein isolate and milk protein concentrate demonstrated zero hydrophobic recovery over time. Scanning electron microscopy showed that cold air plasma treatment of food powders caused minor surface oxidation, though these changes were not observed using FTIR spectroscopy. We suggest that cold plasma treatment has important implications for the production of stabilizer-free food suspensions.     

High voltage atmospheric cold plasma technology as a food safety intervention for decontamination of cutting tools during ready-to-eat poultry meat slicing

This study aimed to build a prototype that integrates a cold plasma capability into a manual meat slicer while it is in operation to minimize cross-contamination from the circular cutting blade. A high voltage atmospheric cold plasma (HVACP) generator was attached to a meat slicer with a rotating 22.5-cm diameter stainless steel slicing blade. The meat slicer with the installed cold plasma generator was contained within a sealed, clear acrylic box. Listeria innocua (LI) was selected as the test organism, and initial testing was performed on stainless-steel coupons in room air at a relative humidity ranging from 30 to 90% for treatment times up to 240 s. Results found that 240 s and 90% RH showed a 3.0-log reduction of LI. These conditions were then replicated using “dirty” stainless-steel knife while rotating. The results showed only a 0.5-log LI reduction. The gas was changed from air to MA65 gas blend (65% O₂, 30% CO₂ and 5% N₂) and then a 1.91 log LI reduction was achieved on the “dirty” knife.Industrial relevanceDue to the rapid processing speeds required in the food industry, it is difficult to assure the complete cleanliness of the tools and surfaces used at all times, and then, operations like the cutting /slicing step are still one of the critical points for cross-contamination during meat processing. High voltage atmospheric cold plasma (HVACP) is a practical intervention that has the potential to deliver a continuous, in-situ decontamination of the knife during operation to mitigate the risk of cross-contamination. The developed prototype, as shown in this study, can deliver beneficial results in short treatment time and with minimal inputs of air and electricity, without heating effects, minimizing the use of water, or the use of sanitizers.     

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

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.     

丝织物的大气压等离子体液相沉积处理

为提高丝织物表面的拒水、拒油性能,较好的控制沉积涂层的质量,将等离子体与液态沉积液结合,采用介质阻挡放电装置,利用高频高压电源在大气压下通入惰性气体氦（He）产生辉光放电等离子体,通过超声喷嘴将液相单体雾化并喷射入等离子体区域,使之在处理物表面上进行等离子体沉积聚合。应用此工艺对丝织物处理,将全氟庚烷单体经过超声雾化,注入大气压辉光放电区域中,实现了在丝织物表面沉积拒水性涂层。通过SEM观察和ATR-FTIR以及接触角测量,分析处理前后纤维表面形态和结构的变化,得出在不同工艺参数下丝织物表面的全氟庚烷沉积率变化规律。结果表明, 纤维表面成功沉积致密膜层,织物表面水接触角增大,拒水性能极大地改善。     

Enhanced bonding strength of heat-treated wood using a cold atmospheric-pressure nitrogen plasma jet

In this work, the bonding strength enhancement of heat-treated wood using a cold atmospheric-pressure nitrogen plasma jet for several lengths of treatment time was investigated. The enhancement of bonding strength was assessed by measurement of the contact angle of aqueous adhesive and water borne finish along with determination of compressive shear strength of wood samples bonded with an aqueous adhesive and pull-off strength of a water borne finish coating on wood samples. Additionally, the elemental composition and crystallinity index of the heat-treated wood surface were characterized using X-ray photoelectron spectroscopy and X-ray diffraction. As expected, the measurements demonstrated that contact angle decreased after atmospheric-pressure nitrogen plasma jet treatment, and the optimal treatment time was 100 s. X-ray photoelectron spectroscopy shows that hydrophilic groups such as C=O, OH, and COOH appeared on the surface of the HW. The atmospheric-pressure nitrogen plasma jet treatment had a positive effect on the crystallinity of heat-treated wood because of a slight degradation of hemicelluloses. Increasing the bonding strength of heat-treated wood is beneficial for broadening the fields of its applications.     

常压非热等离子体源及其在纺织整理中的应用

综述了常压介电屏蔽放电（DBD）产生的非热等离子体在纺织整理中的应用。描述了DBD在常压织物整理和等离子体化学中的许多潜在优势。DBD（无声放电）是一种非热等离子体放电,在较宽的温度和压力范围内操作简便。常压下,许多独立的细电流丝之间会发生电击穿,这些短暂的带有电子能量的微放电具有瞬时高压辉光放电性质,非常适合背景气体原子或分子的激发和离解。     

Hydrophobic recovery of atmospheric pressure plasma treated surfaces of Wood-Polymer Composites (WPC)

In this study, the behavior of atmospheric pressure plasma treated surfaces of Wood-Polymer Composites (WPC) was investigated as a function of time and environmental conditions. The surfaces of injection molded WPC based on polypropylene (PP) and polyethylene (PE) were treated by a dielectric barrier discharge (DBD) and subsequently aged under various conditions. The wettability as an indicator for change of the composite surface was assessed using water contact angle. In addition, a calculation for half-time of the contact angles was developed to predict the time span which is needed for recovery of hydrophobicity. The results showed a major influence of temperature and time, whereas the humidity only at storing conditions of 60?°C and 75% relative humidity showed a distinct effect on the activated surface. The effect of DBD treatment was stable for more than one week in the climates 20?°C and 0% RH and 20?°C and 65% RH.     

Modification of wool fibers by atmospheric pressure plasma treatment

Shrink‐proofing processing of wool fabrics by vacuum plasma treatment has been studied for many years. However, as a wool shrink‐proofing processing method, discharge treatment under atmospheric pressure, such as corona and low‐temperature electric plasma treatment, has been studied recently. In this study, an attempt was made to improve shrink‐proofing and other properties of a wool fabric by low‐temperature plasma treatment. The wool fabric was treated by pulsed atmospheric pressure plasma using a dielectric barrier discharge apparatus of the Institute of Textile Technology at Denkendorf by varying the power and flow rate of air. Shrink‐proofing, dyeing yield and water‐absorbing properties increased to a greater degree with the increase in the treatment time. However, the effect was saturated at 3 min. On the other hand, hysteresis of shearing property at large shear angle (2HG5), which is one of the mechanical parameters for measuring fabric hand by the Kawabata evaluation system (KES), becomes larger with the treatment time. It can be concluded that shear hysteresis value is related to the improvement in shrink‐proofing and other properties of the wool fabric.     

基于双层微纳米纤维膜的气液固三相体系构建及其光催化性能

为提升石墨相氮化碳(g-C₃N₄)的光催化降解性能,通过静电纺丝技术制备了亲疏不对称的双层纳微纤维膜,其中疏水层为聚苯乙烯纤维膜,亲水层为以聚丙烯腈/聚乙烯吡咯为载体的g-C₃N₄/酞菁铁(FePc)异质结催化膜,对其表面形貌、化学结构和光吸收性能进行表征,并考察了对染料废水的光催化降解作用。结果表明:水接触角分别为140°和12°的疏水层和亲水催化层可紧密结合,其中催化层中g-C₃N₄和FePc在纤维膜上分布均匀,且FePc的引入将纤维膜的光吸收范围拓展至800 nm;在染料的光催化降解中,疏水层可作为气体通道将空气中的O₂传输至亲水催化层,从而形成气液固三相接触的反应体系,有效促进O₂对g-C₃N₄导带光生电子的俘获,使其光催化活性较常规二相体系提升3.1倍。     

The removal of impurities from gray cotton fabric by atmospheric pressure plasma treatment and its characterization using ATR-FTIR spectroscopy

Gray cotton fabric shows hydrophobic characteristics due to presence of non-cellulosic impurities in outermost layers of cotton fiber. In the present study, atmospheric pressure plasma treatment for the removal of the non-cellulosic impurities from gray cotton fabric is investigated. Gray cotton fabric is treated with air dielectric barrier discharge at different time interval, and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). Different species formed in plasma are identified using optical emission spectroscopy. The results clearly show that the plasma treatment improves wettability of gray cotton which is due to the removal of non-cellulosic impurities and due to the formation of polar carboxylate group. Removal of wax after plasma treatment is clearly reflected in ATR-FTIR spectra as disappearance of symmetric and asymmetric stretching of alkyl group at 2852.24 and 2917.81?cm^?1. Further, ATR-FTIR spectroscopy provides a fast and satisfactory assessment of removal of impurities from cotton surface when untreated and plasma-treated cotton fabric is exposed to HCl vapor and subsequently spectra are collected. We observed a strong carboxyl peak is induced at 1749?cm^?1 in case of untreated cotton. While for plasma-treated cotton fabrics substantial variation in the intensity of 1641 and 1749?cm^?1 peak is observed with increase in plasma treatment time. The morphological changes observed by SEM are in accordance with ATR-FTIR results. The results are compared with conventionally (alkaline scouring) treated cotton fabric. The study reveals that atmospheric pressure plasma has potential to become dry and environment friendly process to improve wettability of gray cotton fabric.     

Non-thermal atmospheric gas plasma device for surface decontamination of shell eggs

A resistive barrier discharge (RBD) prototype able to generate gas plasma at atmospheric conditions was set up. The discharge was electrically characterized and the plasma glow was analysed by optical emission spectroscopy. The decontamination power of the device was assessed on samples of shell eggs experimentally inoculated with Salmonella Enteritidis and Salmonella Typhimurium (5.5–6.5 Log CFU/eggshell) and placed in the treatment chamber. Different decontamination times (10, 20, 30, 45, 60 and 90 min) and relative humidity values (RH) of the gas mixture in the chamber (i.e. 35% and 65%, at 25 °C) were considered. All samples were treated in the plasma after-glow chamber where the measured temperature was not much higher than the room temperature, minimizing the risk of egg quality alterations.