Cold Oxygen Plasma Treatment Research Articles

Effect of oxygen plasma-treatment on surface functional groups, wettability, and nanotopography features of medically relevant polymers with various crystallinities

The surface properties of polymeric biomaterials play a crucial role in their biocompatibility and performance. This study explores the application of cold oxygen plasma treatment as a versatile technique for surface modification of polymeric materials with different degrees of crystallinity: crystalline high-density polyethylene (HDPE), crystalline-amorphous poly(chloro‑paraxylylene) (parylene C), and amorphous aromatic polyether-based polyurethane (PU). The investigations focus on the generation of surface functional groups and hydrophilicity, as well as nanotopography. X-ray photoelectron spectroscopy (XPS) analysis confirmed the generation of oxygen-containing functional groups, resulting in controlled wettability (water contact angle), while atomic force microscopy (AFM) showed topography modifications in the nanoscale. At the same time, it was revealed that oxygen plasma treatment did not affect the bulk properties (confirmed by TG and XRD). The effects of the same plasma treatment conditions varied significantly among the different polymers studied, depending on their crystallinity. This was discussed in terms of the preferential etching of amorphous regions in the polymeric structures. The findings emphasize the advantages of oxygen plasma treatment for tailoring the surface properties of polymeric biomaterials, highlighting its significance for biomedical applications.

Factors influencing the nutritional composition, quality and safety of dried fishery products

Dried fishery products are popular processed food items throughout the world. Nowadays, the demand for nutritionally rich and safe dried fishery products is increasing. A substantial quality loss in dried fishery products occurs due to the chemical, microbiological and non-enzymatic browning reactions during handling, processing, drying, packaging, storage and distribution lead to influence the safety of the products. However, factors influencing the quality and safety of dried fishery products are poorly understood. Therefore, this review article discussed various quality and safety aspects of dried fishery products, such as raw material quality and pre-treatment, drying methods, additives use, extrinsic factors, irradiation, cold oxygen plasma treatment, corona discharge plasma, high hydrostatic pressure, packaging methods and materials used, storage condition and temperature, and so on, all of which have an impact on the final product. The ultimate aim of this study was to gain a better understanding of the current state of quality in dried fishery products and the techniques for improving it, which will aid processors in ensuring the quality and safety of dried fishery products for consumers in the long run. This review could also be used as a guide for future research and development of dried fishery products as well as ensuring consumer’s safety for both domestic and foreign markets.

Chemical activation and cold plasma surface modification of olefin plant waste pyrolytic coke and its effectiveness for elimination of an azo dye from aqueous solutions

Pyrolytic coke is formed in olefin plants of petrochemical complexes that is considered as a detrimental waste material. However, it could be used as a suitable carbon source for value-added activated carbon production due to its high carbon and low sulfur content. The aim of this is to convert Pyrolytic coke into activated carbon by KOH activation and cold oxygen plasma treatment as the chemical and physical treatment methods, respectively. First, effective parameters of plasma modification such as vacuum pressure and retention time as well as effective parameters of chemical activation such as temperature, activation time and weight ratio of KOH to the coke was optimized by the adsorption performance of Acid Yellow 17 dye (AY17). In the second step, the novel plasma treated activated pyrolytic coke was introduced at the optimum conditions. Vacuum of 0.2 mbar and residence time of 15 min were determined as optimal plasma modification conditions with almost 40 % AY17 removal efficiency. For chemical activation, temperature of 825 °C, activation time of 1 h and KOH to coke ratio of 1:2 were obtained as the optimal conditions. Optimum waste-base adsorbent's characteristics were investigated by SEM, BET, XRD, XRF, FTIR, CHNS and AFM analysis. Surface area of plasma treated activated pyrolytic coke (PTAPC) was reached up to 102.4 m2/g. Isotherm model and adsorption kinetics showed that this adsorbent follows the Langmuir isotherm with a maximum adsorption capacity of 48.52 mg/g and the pseudo second-order kinetic model. Adsorption at acidic pH, especially at pH = 3, has the best results. The main adsorption mechanism at pHs below zero potential is electrostatic interaction between the dye sulfonate anions and oxygenated groups such as hydroxyl.

Interfacial shear strength enhancement of polymeric macro-fibers via plasma treatment

This work deals with a utilization of a plasma treatment of polymeric macro-fibers used as reinforcement in the cement composites. Commercial fibers BeneSteel were plasma treated to reduce their weaknesses – smooth and chemically inert surfaces and thus to enhance an interfacial shear strength between them and the cement matrix. The low-pressure cold oxygen plasma treatment was done for both physical (roughening) and chemical (surface activation via active polar groups) surface modifications. A plasma exposition time differed between 5 and 480 seconds, while the surface changes were observed. It was shown that the most effective treatment time was equal to 30 seconds, as proven by a wettability measurement between fibers and demineralised water. To determine the interfacial shear strength between reference and chosen modified fibers, pull out tests from the cement matrix was performed. Finally, thus treated fibers were used as the reinforcement in concrete composites. Concrete samples having dimension equal to 100 × 100 × 400 mm were tested in the three-point bending test. We focused especially on the post-cracking response of tested samples. The results showed that the post-cracking residual flexural strength of samples reinforced with plasma treated fibers was higher by 30 %. It was find out that the utilization of plasma treated fibers is more effective if compared to reference ones. Copyright © 2017 VBRI Press.

USE OF FINELY GROUND RECYCLED CONCRETE FOR IMPROVEMENT OF INTERFACIAL ADHESION IN FIBER-REINFORCED CEMENTITIOUS COMPOSITES

This paper deals with an improvement and an assessment of a polymeric macro-fibers adhesion to the cement matrix. For this purpose, two approaches were employed – (i) roughening of fibers using a plasma treatment and (ii) an addition of finely ground recycled concrete (amount 30 wt. %) to the matrix ensuring the roughness of interfacial zones. Polyethylene terephthalate (PET) and polypropylene (PP) fibers, both ca. 0.3mm in a diameter, were used. These were surface roughened using a cold oxygen plasma treatment and then observed by means of the scanning electron microscopy. Consequently, pull-out tests of an individual fiber embedded 25mm in the matrix were performed, while the force needed for fiber pullout was recorded. Results have shown that plasma treated fibers reached on a better adhesion with the matrix by up to ca. 5% (PET) and 20% (PP), if compared to reference fibers. When recycled concrete was used, the adhesion increased further by about 5–10% for both fiber types.

Surface modification of polylactic acid (PLA) and polyglycolic acid (PGA) monofilaments via the cold plasma method for acupoint catgut-embedding therapy applications

Polylactic acid (PLA) and polyglycolic acid (PGA) monofilaments have been the most recently, widely used acupoint catgut-embedding therapy (ACET) biodegradable materials. However, their poor hydrophilicity and cell adhesion are common limitations during applications. To improve their surface properties, modification technologies should be generally applied. This paper firstly adapted polymer chips to produce four types of PLA and PGA monofilaments, and then attempted cold oxygen plasma treatment for surface modification. Afterwards, the modified monofilaments were fully characterized with respect to structure, mechanical and in vitro properties. The results showed that both the PLA and PGA monofilaments became coarser after modification, and their hydrophilicity was improved, while their weight and diameter sizes were slightly decreased. The tensile properties and flexibility of the modified samples changed little, and their swelling ratio increased sharply. All the prepared samples exhibited good cell viability, with more than 75% of cells being viable. Sample PM-PLA2 (plasma-modified PLA2) and sample PM-PGA2 (plasma-modified PGA2) presented the largest cell attachment ratio (cultured for 48 h) at 52.16% ± 1.05% and 58.39% ± 2.07%, respectively. In sum, this cold plasma method successfully improved the hydrophilicity and in vitro properties of PLA and PGA monofilaments, while retaining the other excellent properties, and warrants further study to develop new PLA and PGA-embedding materials with outstanding clinical efficacy.

Generation of hydroxyl radicals and singlet oxygen by particulate matter and its inorganic components

Particulate matter (PM) can strongly affect redox biochemistry and therefore induce the response of the immune system and aggravate the course of autoimmune diseases. Nanoparticles containing transition metal compounds possessing semiconductor properties (TiO2, ZnO) may act as photocatalysts and accelerate the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). In this study, the NIST standard reference material, SRM 1648a, has been analyzed in terms of this consideration. Organic compounds present in SRM 1648a were removed by cold oxygen plasma treatment. Samples of SRM 1648a with removed organic content (<2% of organic carbon, <1% of nitrogen) were obtained within 2 h of this treatment. The treatment did not affect the morphology of the powder. The reference material and PM2.5 collected in Kraków are composed of smaller particles and nanoparticles forming aggregates. The efficiency of (photo)generation of hydroxyl radicals and singlet oxygen was compared for original and organics-free samples. The analyzed samples showed the highest activity towards ROS generation when exposed to UV-vis-NIR light, moderate under UV irradiation, and the lowest in dark. Data collected in the present study suggest that the organic fraction is mostly responsible for singlet oxygen generation, as almost twice higher efficiency of 1O2 generation was observed for the original NIST sample compared to the material without the organic fraction. However, particulate matter collected in Kraków was found to have a five times higher activity in singlet oxygen generation (compared for original NIST and Kraków dust samples).

Surface modification of polypropylene mesh devices with cyclodextrin via cold plasma for hernia repair: Characterization and antibacterial properties

Light weight polypropylene (PP) mesh is the most widely used implant among all other synthetic meshes for hernia repair. However, infection is the complication associated to all synthetic meshes after hernia repair. Thus, to manage mesh related infection; antibacterial drug is generally loaded to surgical implants to supply drug locally in mesh implanted site. Nevertheless, PP mesh restricts the loading of antibacterial drug at operated area due to its low wettability. The aim of this study was to introduce a novel antimicrobial PP mesh modified with β-cyclodextrine (CD) and loaded with antimicrobial agent for infection prevention. A cold oxygen plasma treatment was able to activate the surfaces of polypropylene fibers, and then CD was incorporated onto the surfaces of PP fibers. Afterward, triclosan, as a model antibacterial agent, was loaded into CD cavity to provide desired antibacterial functions. The modified polypropylene mesh samples CD-Tric-1, CD-Tric-3 exhibited excellent inhibition zone and continuous antibacterial efficacy against E. coli and S. aureus up to 6 and 7 days respectively. Results of AFM, SEM, FTIR and antibacterial tests evidenced that oxygen plasma process is necessary to increase chemical connection between CD molecules and PP fibers. The samples were also characterized by using EDX, XRD, TGA, DSC and water contact angle.

Assessment of cold oxygen plasma technology for the inactivation of major foodborne viruses on stainless steel

This study investigated the efficacy of cold oxygen plasma (COP) for inactivation of murine norovirus-1 (MNV-1; a human norovirus [NoV] surrogate) and hepatitis A virus (HAV) on stainless steel surfaces. Decrease in the MNV-1 and HAV titers resulting from 10 to 300 s of COP were 0.27–3.89 and 0.77–2.02 log PFU/ml, respectively. The Weibull model was used to calculate D-values of 1, 2, and 3-log reductions as the treatment times for MNV-1 (R2 = 0.95, RMSE = 0.08) and HAV (R2 = 0.96, RMSE = 0.05). The D = 2 and D = 3 values for MNV-1 (0.72 min for D = 2, 4.98 min for D = 3) were less than those for HAV (1.43 min for D = 2, 9.99 min for D = 3). However, there was no significant difference in values for D = 1 by COP between MNV-1 (21.65 s) and HAV (25.10 s). COP treatment on food contact surfaces could be effective for inactivation of NoV and HAV.

Novel preparation of activated carbon by cold oxygen plasma treatment combined with pyrolysis

This study reports an original approach based on the inserting of a cold oxygen plasma treatment as oxidation stage between two pyrolysis processes for the preparation of an activated carbon from vinasse as a waste from the distillation of fermented sugar beet. The effects of pyrolysis temperature and plasma application time on the structural and morphological properties of the prepared carbon materials were investigated by Thermal Gravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX) techniques and gas adsorption measurements (BET). The results of the different conditions indicated that the structure properties of the obtained activated carbon were significantly dependent on the pyrolysis temperature. As an optimum condition, the application of oxygen plasma for 5min between pyrolysis processes at 1000°C provided an eligible activated carbon with surface area (832.3m2/g) and mainly microporous structure. After preliminary examinations on various dyes, the adsorption performance of the activated carbon with highest surface area was specifically evaluated using methylene blue as a model dye in aqueous solution as functions of various operating parameters. Langmuir adsorption capacity (909.091mg/g) of the prepared activated carbon toward methylene blue was superior than most of the other adsorbents.

Effect of cold oxygen plasma treatment on mechanical properties of phenylenebenzobisoxazole fiber-filled cross-linked polyethylene composites

Mechanical strength of phenylenebenzobisoxazole (PBO) fibers and cross-linked polyethylene (XLPE) matrix composites were studied with particular interest on the effects of oxygen cold plasma-treated fibers. PBO fibers were treated in a radio frequency plasma reactor using oxygen for different treatment times to increase the interface adhesion. Tensile tests on PBO fibers showed that plasma treatment caused an increase in average tensile strength compared with untreated fibers. Fracture analysis confirmed the increase in interfacial adhesion due to oxygen plasma treatment.

Dynamic Wettability of Different Adhesives on Wheat Straw Surface Modified by Cold Oxygen Plasma Treatment

The effects of cold oxygen plasma treatment on the exterior and interior surfaces and wettability of wheat straw were investigated. The wheat straw was treated with oxygen plasma for 150 s, and the radio-frequency power was set at 100 W. The surface wettability was evaluated by measuring the contact angles and the K values of urea-formaldehyde, phenol-formaldehyde, and methylene diphenyl diisocyanate resins. Specimens with different gluing surfaces were bonded together with urea-formaldehyde and phenol-formaldehyde and then hot-pressed to assess bonding strength. Results indicate that the dynamic wettability and the shear strength of wheat straw were remarkably improved after it was exposed to the cold oxygen plasma. Additionally, the adhesive type and the wheat straw surface characteristics had significant effects on the dynamic wettability and bonding strength of both untreated and plasma-treated wheat straw.

Inactivation kinetics of cold oxygen plasma depend on incubation conditions of Aeromonas hydrophila biofilm on lettuce

Disease outbreaks from fresh produce have been increasing as a result of the increasing global consumption of produce. We evaluated the efficiency of cold oxygen plasma (COP), a new technology for the decontamination of fresh produce, in reducing biofilm of Aeromonas hydrophila, an emerging food-borne pathogen on lettuce. Lettuce leaves were inoculated with A. hydrophila at different temperatures to form biofilm and planktonic populations, and the inactivation kinetics of COP were determined using a modified Weibull model. To elucidate the antimicrobial mechanism of COP, we used field emission scanning electron microscopy (FESEM) and a quorum sensing (QS) assay. We found that 5min of treatment with COP significantly (p<0.05) reduced the biofilm populations of A. hydrophila on lettuce by 5.0-log incubation at lower than 15°C, whereas biofilm populations displayed enhanced resistance to COP treatment at higher temperatures (≥15°C). Planktonic populations also decreased by >5.0-log within 15s treatment of COP by incubating at any temperature. The mean Td-values for a 5-log reduction (analogous to the traditional D-value) ranged from 4.4–8.1s and 1.84–25.33min for the planktonic and biofilm populations, respectively. However, higher temperatures (≥15°C) resulted in a significantly higher QS (p<0.05) as well as biofilm formation and internalization in stomata, suggesting that higher biofilm formation and internalization might be the main factors mediating resistance to COP. In summary, this study highlights the impact of temperature on the modulation of QS, biofilm formation, internalization, and COP resistance in lettuce.

Dynamic adhesive wettability of poplar veneer with cold oxygen plasma treatment

Effects of cold oxygen plasma treatment on activating the surface of poplar veneers and improving its wettability were investigated. The veneers were treated with cold oxygen plasma for 1, 3, 5, 7, and 9 min, and aged in air for 1, 3, 7, 14, 21, and 28 days. The dynamic adhesive wettability of veneers was assessed using the contact angle, K-value analysis, and surface free energy. The shear strength of three-layer panels produced from untreated and cold oxygen plasma treated veneers was examined. The results showed that the wettability of veneer was significantly improved after cold oxygen plasma treatment, leading to the enhancement of shear strength of panels. The optimized treatment time should be 7 min. Aging effect of treated veneers showed that the veneer surface wettability degraded within the first 7 days and thereafter changed slightly.

Compound Finishing of Bombyx mori Silk: A Study of Cold Oxygen Plasma/Titania Sols Treatments and Their Influences on Fiber Structure and Performance

Degummed Bombyx mori (B. mori) silk fabrics modified by cold oxygen plasma (COP) and/or titania sols (TSs) were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, field emission scan electronic microscopy (FE-SEM), thermo-gravimetric and differential thermal analysis, and ultraviolet (UV) transmittance methods in this study. FT-IR analysis demonstrated that titania particles were associated with B. mori silk fibers by forming organic–inorganic hybrid blends. Processing sequences of COP and TSs, and curing conditions showed significant impacts on the crystalline, thermal, micro-morphological, and UV resistant characteristics of silk fabrics. Crystallinity index by both area and height methods, and crystallite sizes of silk fabrics were calculated as well. Results showed that crystallinity index of finished samples approximate to that of degummed silk fabric could be obtained by applying TSs and curing at 160 °C for 2 min prior to COP treatment, or vice versa with lower temperature of 140 °C for 3 min, whereas the crystallite sizes of treated samples increased slightly. The initial decomposition temperatures of finished samples were elevated by 23–35 °C with increased char residues at 600 °C, while the transmittance of UVA and UVB of finished samples decreased by 11.7, 17.7%, respectively. FE-SEM analysis revealed that titania particles were associated on the fiber surfaces with different smoothness.

Plasma activation of carbon fibres for polyarylacetylene composites

Interfacial properties of carbon fibre (CF) reinforced non-polar structure polyarylacetylene (PAA) resin composites were modified through cold oxygen plasma treatment of CF. The effects of plasma treatment on CF were characterized by X-ray photoelectron spectroscopy, atomic force microscope (AFM), and interlaminar shear strength (ILSS). XPS showed that plasma treatment increased the amount of elemental oxygen on fibre surface markedly by introducing more kinds of oxygen groups. AFM images indicated that weak surface regions of fibres had been etched and removed, and the roughness of fibre surface was increased. Furthermore ILSS of CF/PAA composites was improved notably. The influences of treatment time on the plasma oxidation results were studied and optimal treatment time was determined according to the change of ILSS. The conclusion that plasma treatment is an effective method to improve the interfacial properties of carbon fibre reinforced non-polar structural PAA matrix composites, just as doing in polar resin matrix composites, can be drown.

Functionalisation of the carbon nanofibres by plasma treatment

Vapour grown carbon nanofibres (VGCNF) were surface modified through cold oxygen plasma treatment under reduced pressure. The fibre morphology was studied by SEM (scanning electron microscopy) and HRTEM (high resolution transmission electron microscopy). The nanofibres surface functionalisation was elucidated by NaOH-titration, contact angle and surface energy measurements of the carbon nanofibres before and after plasma treatment. Oxygen plasma treatment introduced oxygen containing functional groups (hydroxylic, carbonylic and carboxylic groups) onto the fibre surfaces and also enhanced the fibre surface porosity (by etching) as well as the surface energy. There is yet to be mentioned that the fibre modifications have to occur only in the first few atomic layers. The plasma treatment can be proposed as a suitable method to change nanofibres surface from hydrophobic to hydrophilic.