Effect Of Air Plasma Treatment Research Articles

Effects of air-plasma treatment in enhancing the mechanical properties of oriented strand boards

In this work, through surface modification of poplar strands with a non-thermal type of plasma, we produced oriented strand board (OSB) panels with high loading capacity (fabricated with a target density of 0.7 g/cm3 and phenol-formaldehyde resin in a content of 7%). At the processing power of 4.5 kW, the plasma-induced efficient etching effect and chemical grafting contributed greatly to improving the wettability of strands surfaces, resulting in the 68.3% increase of resin coverage and the formation of consecutive bond-lines within the structures of OSB. Furthermore, the adhesive distribution within wood surface layers and adhesion efficiency were intensively analyzed by means of X-ray computed tomography imaging, the results demonstrated that the plasma-based surface modification considerably increased the penetration depth of the resin into the wood volume, making it easier to form mechanical interlocking in wood-resin interphase. Further nanoindentation analysis on the resin-infiltrated cell walls revealed the substantial reinforcement of bonding interphase after plasma modification. In bonding performance tests, the internal bond strength of plasma-modified OSB reached up to 1.22 MPa, nearly 3.6 times the value recommended by ISO 16894: OSB panels type 4. Meanwhile, the loadbearing property was improved significantly, which was not only reflected in the enhanced bending strength and elastic modulus, but was also confirmed by strain distribution along the thickness direction recorded using digital image correlation technique.

Study on the monolayer dispersion behavior of SnO2 on ZSM-5 for NOx-SCR by C3H6: the remarkable promotional effects of air plasma treatment.

Aiming to fabricate more practical catalysts for NOx-SCR with C3H6, SnO2/ZSM-5 having different SnO2 loadings was prepared and treated with DBD air plasma. The dispersion of SnO2 on the H-ZSM-5 support and their interactions were investigated with both experimental methods and DFT calculations. SnO2 displays evident monolayer dispersion behavior, getting a threshold of 0.271 mmol 100 m-2 support. Plasma treatment improves significantly the SnO2 dispersion, hence amplifying the monolayer dispersion threshold to 0.380 mmol 100 m-2. XPS and DFT calculations have testified that plasma treatment strengthens strongly the SnO2-ZSM-5 support interaction, mainly through donating electrons from Sn4+ to Al3+ in the support, thus improving the dispersion of SnO2 at the same loadings. Consequently, the catalytic performance is remarkably improved because of the generation of more abundant surface acid sites and superoxide species devoted to the reaction. The sample having a SnO2 loading near the monolayer dispersion threshold shows the optimal activity in the corresponding catalyst series, demonstrating an evident threshold effect. Over SnO2/ZSM-5, the reaction goes through a Langmuir-Hinshelwood pathway, involving the adsorption and activation of both NO and C3H6 molecules. Surface mono-dentate/bridged-nitrate and carbonate species are the main reaction intermediates.

Effects of air plasma treatment on water uptake of wheat and barley seeds

In this study, radio-frequency (RF) plasma was used to treat the surface seeds of wheat and barley. Plasma treatment was conducted for different exposure times (1, 5, and 10 min) and at different powers (20, 50, 80 and 100 W), keeping the air gas pressure fixed at 1.0 torr. It was observed that the seeds that were exposed to 80 W of plasma power for 10 min. exhibited a higher water absorption rate. The weight gain of the treated wheat and barley seeds was increased by 62% and 12%, respectively, compared to the control sample (untreated seeds). Spectroscopic and microstructural analyses of the seed surface indicated that the plasma treatment caused chemical etching, which improved the water uptake of the treated seeds.

Modification of starch using low pressure radio frequency air plasma

Cold plasma is one of the emerging nonthermal food processing technologies recently drawn interest as a chemical-free biopolymer modification method. In the present study, two starches (corn and tapioca) were exposed to low pressure radio frequency plasma at 40 W and 60 W for 10 and 20 min. The effect of air plasma treatment on the starch properties was determined by measuring amylose content, swelling power, powder flowability properties, gelatinization temperatures and pasting properties. The amylose content of corn and tapioca starches was observed to decreased and increased respectively. Increase in water binding capacity and swelling power of both starches. The results of pH showed partial oxidation of starches as evident from the decrease in pH. Rapid visco analyzer showed an increase in final viscosities after the plasma treatment. The increase in viscosities is the result of higher amounts of leach out of particles from the starch granules. Plasma treated corn starches exhibited lower peak temperatures and enthalpies whereas it increased in tapioca starches. X-ray diffractogram revealed an A-type pattern of both starches and plasma treatment did not show any significant effect on the crystallanity pattern. Cold plasma offers a unique route for starch modification without affecting its bulk properties.

Evaluation of parameters affecting adhesive strength of high build epoxy coatings on textured and plasma treated metallic substrates

Epoxy coating systems have been used throughout the years for protecting critical industrial assets. To ensure superior coating adhesion and longevity, abrasive blasting has been traditionally employed to texture metallic surfaces. Though a large variety of abrasives are available in the industry, coal slag (aluminium silicate) and garnet (mineral abrasive) have remained popular choices until now owing to their easy availability. However, depleting reserves of coal slag owing to stricter environmental regulations and shortage of good quality garnet have fueled the need to identify substitutes. This work is focused on evaluating the effect of surface texturing on adhesive strength of epoxy coatings using two novel abrasive types – olivine (obtained from dunite rock) and calcium silicate (iron furnace slag) which are available in abundance and present an excellent alternative. The surface textures of various blast cleaned mild steel (A36) and stainless steel (316L) substrates were evaluated using a combination of techniques namely, optical profilometry (spatial parameters), replica tape method as per ASTM D 4417 (Method C) (height parameter) and scanning electron microscopy (Secondary electron imaging/energy dispersive X-ray spectroscopy analyses) for embedded particle composition analysis. Correlations were drawn to the wettability of metallic substrates textured using the selected abrasives. Adhesive strength tests on high build epoxy coatings, performed in accordance with ASTM D4541 revealed exceptional performance using various grades of both olivine and calcium silicate abrasives. The effect of air plasma treatment on adhesive strength of epoxy coatings applied on mild steel substrates were also studied.

The effect of air plasma treatment at atmospheric pressure on thermally modified wood surfaces

This 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.

Time‐dependent changes of surface properties of polyether ether ketone caused by air plasma treatment

AbstractThe effect of air plasma treatment on wetting and energy properties, surface composition and morphology of polyether ether ketone (PEEK) was investigated. The influence of the storage time on the surface properties of plasma‐treated polymer plate was also examined. The properties were determined by advancing and receding contact angle measurements, Fourier transform infrared spectroscopy supported by theoretical spectrum modelling, X‐ray photoelectron spectroscopy and optical profilometry. Three theoretical approaches were used in the determination of the apparent surface free energy of the untreated and plasma‐treated PEEK samples from the measured contact angles of probe liquids (water, formamide, diiodomethane): the contact angle hysteresis method, the Owens and Wendt approach and the Lifsthitz − van der Waals acid–base approach. It was found that air plasma treatment of PEEK causes significant chemical and morphological changes of the polymer surface, which are reflected in the decrease of contact angles from 83.4° to 11.7° for water after 180 s plasma treatment. This is due to the formation of polar functional groups resulting in the increase of the surface hydrophilicity. After plasma treatment the apolar component of the surface free energy practically does not change, while the polar component increases significantly, especially for plates treated for 180 s, from 0 to 19.6 mJ m−2. In addition, the modified PEEK surface is not stable during storage and it acquires more hydrophobic character. © 2016 Society of Chemical Industry

Effect of air plasma treatment on mechanical properties of bioactive composites for medical application: Composite preparation and characterization

The aim of this study was to fabricate unidirectional bio-glass fibers (BGF) (13-93)-reinforced polylactic acid (PLA) composites with improved mechanical properties for a bone plate to heal the weight-bearing long-bone fractures. Various exposure times of air plasma (30, 60, 90 and 120s) on BGF fibers were studied, and the most suitable conditions were determined for the fabrication of the BGF/PLA composite. Mechanical properties, microscopic characteristics, in vitro degradation and the bioactivity of the BGF/PLA composites were evaluated. Fatigue life of 30s plasma treated composites completed 1 million cycles when actual loading conditions (10–20% body weight) were used. 30s plasma treated specimens showed increase in tensile strength, flexural strength and interlaminar shear strength as 31%, 13.5% and 33%, respectively. The SEM image of fractured surface of 30s plasma treated composite suggested that the failure was shifted to the PLA which is evidence of superior bonding between fiber and PLA matrix. Moreover, a bone-like calcium-phosphate layer was precipitated on the surface of degraded composite that is essential for bone healing.

The study of air-plasma treatment on corn starch/poly(ε-caprolactone) films

In spite of usefulness of synthetic polymers in every aspects of life, the environmental hazards limit their use. Starch based biodegradable polymers is one of the solutions to it. Packaging has a major share in use of synthetic polymers. For packaging application, it is necessary to have good surface and barrier properties of the material. Plasma surface modification of materials is a promising solution to enhance surface properties. In the present paper, cornstarch/poly(ε-caprolactone) (CSPCL) films were treated in air-plasma for different durations of time. The effect of air-plasma treatment on surface properties and biodegradation was studied. The extent of etching was evaluated from weight change (%) study. Changes in surface chemical composition were analyzed using ATR-FTIR and XPS. The contact angle and surface free energy (SFE) study indicate that air-plasma treatment leads to hydrophilization of CSPCL films. The changes in surface topography of plasma processed films were analyzed using AFM and SEM. The roughness caused by etching and increase in surface free energy facilitates the improvement in adhesive properties like printability and peel strength. Changes in barrier properties were studied using water vapor and oxygen transmission rate. Effect of air-plasma treatment on biodegradation of treated and untreated samples was studied by simulating natural biodegradation conditions in a controlled environment using indoor soil burial method and with a single bacterial system comprising of a commonly occurring soil bacterium, Bacillus subtilis MTCC 121. While the soil system is indicative of biodegradation due to macro as well as micro elements, a single microbial system will identify the interaction between the microorganisms and modified surface thus showing the effect of air-plasma treatment on the degradation process. Biodegradation by indoor soil burial method was assessed by measuring loss in tensile properties and growth of soil micro flora on surface by optical light microscopy (OLM). Biodegradation by B. subtilis was assessed by measuring increase in its number along with the changes it brought about in the sample surface by optical light microscopy and SEM. It was observed that such surface modifications enhanced the biodegradation rate along with finding application in packaging field, thus providing a green solution for the increasing packaging utilization and addressing environmental concerns.

Effect of air plasma treatment on interfacial shear strength of carbon fiber–reinforced polyphenylene sulfide

Plasma treatment, an environmentally safe method, was applied for surface modification of carbon fibers (CFs) and polyphenylene sulfide (PPS) fibers. The morphology, crystallization property, thermal stability, and chemical properties of CF/PPS composites were determined, respectively, by scanning electron microscopy, differential scanning calorimetry, thermogravimetry analysis, and X-ray photoelectron spectroscopy. Interfacial micromechanical performance of CF/PPS composites was investigated by microbond test. The influence of plasma treatment on the apparent interfacial shear strength ( τapp) of CF/PPS micro-composite was systematically evaluated. The plasma treatment of CF reduced the τapp of the micro-composite by 13.7% and that of CFs and PPS fibers by 3.4%. However, the plasma-treated PPS fibers increased the τapp of the micro-composite by 17.1%. The present study demonstrates that matching of polarity between CF and the resin plays a great role in reinforcement of interfacial property.

Effect of air plasma treatment on the dyeing of Tencel fabric with C.I. Reactive Black 5

The Tencel fabrics were treated by the atmospheric pressure plasma with air for different length of time and dyed with the C.I. Reactive Black 5 at 1%, 5% and 10% o.m.f. The effect of the prolonged plasma treatment time was characterized by both the weight loss and the whiteness index analyses, which implied that with the increase of the plasma treatment time, the treated fabrics were lighter and yellower than the untreated ones. The contact angle decreased dramatically from 139° to instantly spread. The results of SEM showed that, with the prolonged treatment time, more significant crater-like surface morphology on the fiber of Tencel samples was formed. Compared with untreated samples, the values of dye bath exhaustion and total fixation effect were higher. But they did not increase with the prolonged plasma treatment time. With the prolonged storage time after the plasma treatment, the result to ageing effect indicated that the values of dye bath exhaustion and total fixation effect reduced. The Integ values for characterizing the coloring effect were evaluated by the CIE system of color measurement. In most cases, the Integ values reached the highest ones when the plasma treatment time was 10 or 20min. When the concentration of the dye bath was low (at 1% o.m.f.), the longer plasma treatment time was, the higher the Integ value was. However, if the fabrics after plasma treatment were stored for 21 days, the longer plasma treatment time did not cause the larger Integ value. When the concentration was 1%, the Integ value increased with the weight loss increasing, which was different from the values of fabrics with 5% and 10% concentration. If the dyeing concentration was low, the fixation had a more significant effect on the color fastness to wet rubbing; in contrast, if the dyeing concentration was high, the surface roughness had a more important effect on it.

Effect of air plasma treatment on the mechanical properties of polyphenylene sulfide/glass fiber cloth composites

In this research study, air plasma-treated polyphenylene sulfide film was used to prepare polyphenylene sulfide/glass fiber cloth composites for improving interfacial adhesion and mechanical properties. The effect of air plasma treatment on the properties of polyphenylene sulfide films was investigated by X-ray photoelectron spectroscopy and water contact angle analysis. According to the X-ray photoelectron spectroscopy analysis, it was found that plasma treatment led to the emergence of oxygen-containing polar groups on the film surface. The intensity of sulfide oxides (S = O and O = S = O) on the surface of polyphenylene sulfide films increased to 79.03% after it was modified by air plasma. Water droplet contact angle analysis indicated that plasma treatment significantly increased the hydrophilicity of the polyphenylene sulfide film. The contact angle was 38 degrees for plasma-treated polyphenylene sulfide film, compared to 78.5 degrees for untreated polyphenylene sulfide film. Tensile strength and notched impact strength of plasma-treated polyphenylene sulfide/glass fiber cloth (50/50) composite increased by 11% (from 248.49 MPa to 275.70 MPa) and 18% (from 52.26 KJ/m2 to 61.43 KJ/m2), respectively, compared with the raw specimen, which was consistent with the morphology analysis result. Meanwhile, the mechanical properties of the composites were improved with the increased discharge power density and treatment time.

Effect of Air Plasma Treatment on Property of PET Fibers Used in Conductive Asphalt Concrete

In this paper, polyester fibers (PET) were treated with low temperature plasma firstly. Then, these plasma treated PET fibers were coated with polypyrrole (PPy) by pyrrole deposition polymerization to impart conductive property to the fibers. Interfacial shear strength (ISS) between PET fiber and asphalt was measured by single fiber pull out test. XPS and SEM were used to characterize the fibers’ surface configuration and analysis the functional groups. The results show that plasma-treatment has a strong effect on the surface morphology, surface elements, electrical property and the ISS.

Fungicidal effects of an atmospheric pressure gas discharge and degradation mechanisms

Studies about interaction of plasmas with microorganisms usually focus on bacteria, bacteria spores or fungal spores; little attention has been paid to plasma treatment of fungal species in their vegetative state. The aim of this work is to evaluate the effect of air plasma treatment at atmospheric pressure on mycelia of the agricultural relevant fungal species Ascochyta pinodella and Fusarium culmorum concerning growth inhibition and morphologic alterations. Radial growth measurements on plasma-treated and heat-treated mycelia plugs and light microscopy imaging of isolated and plasma-treated hyphae were carried out. Growth inhibition of the vegetative state of fungi due to plasma treatment was found as well as deformation and disruption of hyphae.

Capillary flow in microchannels

The surface of microchannels, especially polymer channels, often needs to be treated to acquire specific properties. This study investigated the capillary flow and the interface behavior in several glass capillaries and fabricated microchannels using a photographic technique and image analysis. The effect of air plasma treatment on the characteristics of capillary flow in three types of microfluidic chips, and the longevity of the acquired surface properties were also studied. It was observed that the dynamic contact angles in microchannels were significantly larger than those measured from a flat substrate and the angle varied with channel size. This suggests that dynamic contact angle measured in situ must be used in the theoretical calculation of capillary flow speed, especially for microfabricated microchannels since the surface properties are likely to be different from the native material. This study also revealed that plasma treatment could induce different interface patterns in the PDMS channels from those in the glass and PC channels. The PDMS channel walls could acquire different level of hydrophilicity during the plasma treatment, and the recovery to hydrophobicity is also non-homogeneous.

Tribology of UHMWPE film on air-plasma treated tool steel and the effect of PFPE overcoat

Abstract The effects of air-plasma treatment, film thickness, normal load and sliding speeds on the tribological properties of a thin film of Ultra-High Molecular Weight Polyethylene (UHMWPE) coated onto a tool steel substrate sliding against a Φ 4 mm silicon nitride ball was investigated. Wear tests are carried out on a ball-on-disk tribometer. Air-plasma treatment has enhanced the adhesion of the polymer film to the steel substrate which led to an increased wear life (> 100,000 cycles) and low coefficient of friction (~ 0.14) of the thin film. A film of optimum thickness of 16.3 ± 2 μm shows the maximum wear resistance. The effect of varying loads (0.3, 1, 2 and 4 N) and speeds (200, 400, 600, 1000 and 2000 rpm) on wear life and coefficient of friction were also studied. The dual-film (UHMWPE/PFPE) on the air-plasma pre-treated tool steel surface further increased the wear life (> 200,000 cycles) at a load of 4 N and a rotational speed of 1000 rpm.

Effects of air plasma treatment on tribological properties of hybrid PTFE/Kevlar fabric composite

AbstractHybrid PTFE/Kevlar fabric was surface‐modified by air plasma to improve the adhesion to phenolic resin. The tribological properties of fabric composite with or without plasma‐treated hybrid PTFE/Kevlar fabric were investigated in detail. Friction and wear tests showed that friction‐reducing and antiwear ability of hybrid PTFE/Kevlar fabric composite were remarkably improved after plasma treatment. Scanning electron microscopy and X‐ray photoelectron spectroscopy results indicated that the fiber surfaces were etched and the contents of oxygen and nitrogen increased after plasma treatment, which was favorable for improved fiber/resin bonding strength. The enhancement contributed to the improved tribological properties of hybrid PTFE/Kevlar fabric composite after plasma treatment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of air plasma treatment on mechanical and tribological properties of PBO fabric composites

Friction and wear behavior of one-step or two-step air plasma treated and untreated PBO fabric composites has been evaluated in a pin-on-disc friction and wear tester. Tensile property of impregnated fabric and bond property between fabric and metallic substrate have also been studied. A comparison has been made between untreated and plasma treated fibers by using XPS, FTIR, FESEM and SEM. The results indicated that, air plasma treatment could increase the friction coefficient but decrease the wear rate of the PBO fabric composites. The most suitable condition of plasma treatment was 50 W and 15 min. After two-step plasma treatment, the tensile strength of the PBO fabric was decreased by 40%. While the antiwear property and bonding strength of the PBO fabric composites could be improved by 40–67% and 64%, respectively, which was due to the improvement of the bond property among the fiber, the adhesive and substrate.