جستجوی مقالات مرتبط با کلیدواژه "پلاسما" در نشریات گروه "مهندسی شیمی، نفت و پلیمر"

Research subject: 

Polypropylene (PP) is a thermoplastic polymer that is used in a wide range of applications, including films and sheets, blow molding, injection molding, food packaging, textiles, laboratory and medical equipment, pipes, industrial and construction applications, and the manufacture of automotive components. In the applications of this polymer, improving the surface of PP has been considered. One of the usual methods for improving the surface is the cold plasma method. Plasma is a chemically highly active environment where there are many ions and radicals. In this research, atmospheric pressure gliding discharge plasma was used to increase the hydrophobicity of PP and the surface and depth changes of PP were investigated.

Research approach: 

The depth and surface changes of PP were investigated by radiating the gliding discharge plasma to the PP polymer surface at the different times. FTIR and XRD tests were performed to investigate volume changes and FESEM investigated the surface changes. The hydrophobicity of PP was investigated by contact angle (CA) test and positron lifetime spectroscopy (PALS) was used to investigate shallow depth changes.

The results show that the applied cold plasma did not cause volumetric changes in PP, but caused surface changes and roughness. In this polymer, the contact angle has increased from 30.1 ± 0.1 to 34.4 ± 0.1 and the hydrophobicity of the surface has increased. Examining the changes in holes by PALS test shows that after plasma irradiation the volume of the holes increased from 217 Å3 to 222 Å3 and their intensity decreased. This is due to the heat of the plasma and the energy of its particles.:The results show that the cold plasma caused surface and depth changes and the contact angle increased from 30.1 ± 0.1 to 34.4 ± 0.1 and the hydrophobicity of the surface increased.

Hypothesis: 

The use of plasma is widely used as a method to change polymer surfaces. The use of atmospheric cold plasma has more advantages than other plasma, laser and X-ray methods. This method is simple and it uses inexpensive equipment. Considering the many uses of polyethylene in industry, it can be effective to investigate its changes against cold plasma.

A dielectric barrier discharge (DBD) plasma under atmospheric pressure was used to increase the hydrophobicity of low-density polyethylene (LDPE). After studying the optical emission spectrum (OES) of the produced plasma, its effects on surface and depth changes including surface morphology, chemical composition and polymer crystal structure were studied through scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and positron lifetime spectroscopy (PALS). Moreover, the contact angle analysis (CA) was used to examine the changes in the hydrophobicity of the polymer. 

Based on the data from FTIR and XRD analyses, it was found that plasma irradiation for 180 s affects the depth of a few nanometers of the polyethylene surface and does not cause significant changes in the chemical bonds and crystal structure of the polymer. In other words, plasma radiation can be used for nanometer-scale modification of the surface. On the other hand, the SEM images indicate that the plasma radiation changes the primary flat surface of the polymer into a porous surface. The results of CA analysis, while confirming this issue, show an increase in the hydrophobicity of the polymer after plasma irradiation. The results of PALS spectroscopy also reveal that at micron depth due to the sudden rise in temperature during plasma irradiation, the free volume of the material increases as a result of pore merging.

In this research, a hybrid water falling film plasma reactor dielectric barrier discharge with synthesized zeolite has been used to remove the tetracycline from aqueaus solution. Three types of zeolites have been synthesized by the hydrothermal method based on the ratio of sodium dioxide to silicate dioxide 1, 2 and 3. Infrared spectroscopy (FT-IR),X-ray diffraction (XRD), electron microscopy (SEM), specific surface area, X-ray energy diffraction (EDX), and dot-mapping have been performed on these synthesized zeolites. The tetracycline removal efficiency was about 81% at 60 min in a hybrid reactor designed for synthesized zeolite with a ratio of sodium oxide to silica 1. It was found that this removal percentage is 55% higher than the only plasma system. The percentage of COD removal in hybrid system was about 71% based on the tests performed. Based on experiments related to the effect of active species in the tetracycline removal as a radical trapping experiment, the hydroxyl radical was 12% effective than the superoxide radical. The proposed mechanism is discussed for performingan advanced oxidation reaction to remove tetracycline.

Nowadays, Due to the environmental pollution associated with synthetic dyes, the attention to the application of natural dyes in the textile industry is growing. Natural dyes are environmentally friendly and possess some advantages and disadvantages in comparison with synthetic dyes. One of the main drawbacks of natural dyes is the low exhaustion of textile fibers. To improve the dyeing of textiles with natural colorants, several methods, including metal mordanting, bio-mordanting, treatment with nano-clay, ultrasound, microwave, plasma, ultraviolet, and enzyme, besides the attachment of chitosan, cyclodextrins, and dendrimers to the fibers have been employed. Due to the toxicity of the majority of metallic mordants, the use of bio-mordants and surface modification of fibers by physical and chemical methods are considered as alternative strategies for promoting the natural dyeing of wool fibers. These methods usually improve the sorption of natural dyes by wool fibers and improve the fastness properties of the dyed fibers in most cases. In this paper, the different methods employed to enhance the dyeing of wool fibers with natural dyes are discussed and summarized.

In this study, the effect of plasma modification on improving the adhesion resistance of solvent-borne and waterborne polyurethane coatings in wood was evaluated. For this purpose, wood samples of poplar with a moisture content of 8% and dimensions of 2×10×15 (L×R×T) mm were prepared and their surfaces treated with plasma for 60, 120, 300 and 600 seconds. Then, the surfaces were coated with a solvent and waterborne polyurethane coatings and they were measured by a Pull-off adhesive strength. The results of the contact angle test indicate that the plasma treatment reduced the contact angle and increase the wettability of wood surface. Also, the results of adhesion test after plasma treatment showed that the lowest and highest parameter were related to the solvent-borne (2.9 Mpa) and waterborne (3.4 Mpa) coating respectively, one of the effective factors is increase the surface hydrophilicity of wood by plasma treatment. Plasma treatment had a significant effect on increasing adhesion, so that the adhesion is improved with increasing treatment time, and the highest change in the plasma's effect per unit time was the 60-second. Thus, it can be claimed that the ability of plasma treatment to improve the adhesion of coatings depends on the type of coating resin and plasma treatment time.

Generally, polymer surface engineering has vast applications in biotechnology,membranes, self-cleaning and electronic devices. These applications are based oncontrollable changing in some properties such as surface energy, surface topography, andbiocompatibility of polymer. For choosing a proper method for the surface modificationof polymer, three parameters should be considered carefully. These parameters include:chemical structure of polymer which is focused on strengths and weaknesses of demandedpolymer, the surface properties that we need to achieve after treatment and finally surfacegeometry which is related to the presence or absence of porosity and or chemical andphysical heterogeneity of polymer surface. This research investigates the popular surfacemodification methods like wet chemistry, flame, plasma, UV radiation, laser and grafting.Furthermore, for accurate understanding of quantitative and qualitative changes of surfaceproperties of polymers, the general characteristics of used methods (depth analyzed,resolution, and analytical sensitivity) were briefly mentioned. Some of the popularmethods for include contact angle measurement, Fourier-transform infrared spectroscopy(FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-rayphotoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS), Augerelectron spectroscopy (AES) and scanning tunnelling microscopy (STM).

Dark fermentative hydrogen production is an elaborated multiproduct process that takes place in the absence of light and oxygen. In present paper effect of chemical and physical mutagens on increasing dark fermentative hydrogen production using Enterobacter strain is reviewed. The hydrogen production rate of mutant compared to the wild strain was increased and other metabolite production was decreased by using both chemical and physical mutagens. The various techniques such as testing sugar utilization efficiency, suicide substrate, suicide protons and Voges–Proskauer was used for screening mutant cells. However, the hydrogen production rate as index for selection the best mutant has been considered. Hydrogen production by using chemical mutagens was higher than physical mutagens.

In recent years, the new family of aliphatic polyester that named poly lactic acid, is characterized by particular fiber forms, yarns and fabric constructions. This fibres can be derived from 100% renewable resources such as corn.
A variety of processing applications (scouring, bleaching, enzyme treatment, plasma, thermal setting) that imparts the greatest chemical and physical effect on the Poly(lactic acid) fibres necessitate major attention. The finish of a fabric is often just as important as innovative designs and materials when used for garment manufacture. Finishes can compensate for, or even reduce, fibre embrittlement caused by bleaching, dyeing and printing processes and increase the functionality of the product.
Poly lactic acid is compostable and recyclable, decomposing in 45-60 days in normal composting conditions (typically 50-60 °C and 90-95% humidity). So in this paper the best conditions for processing treatments of Poly(lactic acid) fibre and its effects on the fibre will be reviewed. This was accomplished through a broad literature survey including recent researches and developments in the area.

The adhesion is defined as attraction between the ink and substrate. For good wetting characteristics and consequently achieve acceptable adhesion between the polymer surface and ink, the surface energy of polymeric substrates, is one of the critical parameters and Surface energy of the substrate should be higher than the surface tension of the ink. Despite the sound features of low density polyethylene polymers which make it suited for used in the many industries like packaging, low surface energy of this polymer caused problems with printing on this polymer. Thus, many methods are utilized to improve the printability of this polymer. The objective of this study is in investigating the printability of low density polyethylene after using two methods of treatment; plasma and corona behalf. Contact angle, adhesion tape tests, AFM, SEM was used to determine the quality of provision. Results indicated a better performance of plasma treatment in comparison with corona, both in terms of initial adhesion and durability of this adhesion.

Solid waste is one of the world’s important issues. Common methods for processing solid waste are landfill, incineration, anaerobic digestion, and pyrolysis. All these methods have some disadvantages and weaknesses. So, finding a new technology which is more powerful and reliable is necessary. The newest method is plasma gasification, which was done on a pilot scale for the first time in 1998. The temperatures up to 5000°C is achievable because of the existence of free electrodes inside the plasma arc. These temperatures are able the turn almost everything into syngas at oxygen starve environment. This process has 4 stages: waste pretreatment, plasma gasifier, gas cleaning system, energy recovery system which are described. Syngas is mostly made of H2, CO, CO2. Using two-stage plasma gasification technique, amplification of throughput, and syngas quality are achieved. This technology requires a considerable amount of initial investment, though it is known to be highly profitable economically.

This study was designed to investigate the effect of nano silica particles on the pressure-sensitive acrylic adhesive bonding on polypropylene film. In this work, the effect of plasma treatment on polypropylene films was examined. Selected variables including plasma treatment time, power and gas type at three levels were considered. Results were analyzed by Taguchi method and optimum condition of high adhesive strength at 7 minutes, power of 100 W and argon gas was obtained. Then varying amounts of silica nanoparticles were added to the acrylic adhesive. Adhesion strength test method was evaluated and the results showed that the strength increases to maximum value at 5.0 weight of nano silica. Functional groups on PP surface following plasma treatment were also detected using ATR- FTIR method; moreover, the etching condition of the surface was examined by both SEM and AFM methods.

Polyvinyl chloride based heterogeneous cation exchange membranes were prepared by solution casting technique. The effect of multi walled carbon nano tubes and also MWCNTs-co-Ag nanolayer composite nanoparticles on electrochemical and antibacterial properties of membranes was studied. The MWCNTs-co-Ag nanolayer composite nanoparticles were prepared by magnetron sputtering method. Scanning optical microscopy images showed uniform particles distribution for the membranes. Also surface modification of MWCNTs by Ag nanolayer caused to more uniformity for the membranes. Results showed that membrane electrochemical properties were improved by using of nanoparticles in membrane matrix. Also the modified membrane containing Multi Walled Carbon Nano Tubes-co-Ag nanolayer showed more suitable electrochemical characteristics and antibacterial property in E-Coli removal compared to others.

Low temperature plasma technology has attracted the attention of several researchers as it is a fast and environmentally friendly method for surface modifcation of textiles. In this study, the effects of plasma treatment on physical and chemical properties of wool fbers including surface morphology, tenacity, surface functional groups and water wicking are reviewed. Due to the etching effect, cold plasma treatment can improve the hydrophilicity and dyeability of wool fbers. The effects of cold plasma treatment on dyeing of wool fbers with different synthetic and natural dyes have been also reviewed. Generally, the surface modifcation of wool fbers using oxygen, nitrogen and argon plasmas can improve the dyeability of wool fbers with anionic dyes. Furthermore, the color fastness properties of the plasma treated wool samples are improved compared with those of the untreated samples.

In this study, the extract of Rhuem Ribes L. flowers was used for dyeing of wool fibers. Oxygen plasma was used as a pretreatment to enhance the dyeability of wool fibers and metal mordant was eliminated from the dyeing process. The surface morphology of the wool fibers before and after plasma treatment was investigated by SEM images. FTIR analysis was employed to study the chemical changes imparted to the wool fibers by plasma treatment. The surface of wool fibers was etched and oxygen containing groups were introduced to the surface of wool fibers. The fastness of the dyed samples to washing and light was measured. The plasma treated samples showed better dyeability as well as good fastness to washing and light.

Plasma treatment is a fast and environmentally friendly process for surface modification of polymeric and textile materials. In this study، the various types of plasma treatment are introduced and the most effective parameters on the treatment are discussed. Furthermore، the application of cold plasma treatment on textile goods is briefly discussed and the research works on modification of polypropylene fibers are reviewed. The cold plasma treatment can improve the wettability، water absorption and adhesion of polypropylene fibers. The plasma treatment has been also used for grafting of different monomers، drug، and nanoparticles on the surface of polypropylene fibers.

In recent years, there is a strong incentive to study and develop processes that would convert methane into more valuable chemical and petrochemical products. Among various schemes of methane conversion, oxidative coupling of methane (OCM) is promising process to upgrade natural gas. In this article, effective parameters i.e. selectivity, conversion and yield in differential conditions of this process have been investigated. Then some of kinetic models in the gas phase and catalyst surface proposed in literature have been analyzed.

The production of nanopowders is one the most noticeable applications of induction plasma. An aim of the work is to extend the thermal plasma technique to the synthesis of nanosize nitride based composite powders and to determine an influence of process parameters on characteristics of produced powders. The nanosize nitride –based composites are prepared by evaporation of coarse commercially available powders of chemical elements such as Mo, Cr, Ti, Zr and subsequent condensation of products into a inductively coupled nitrogen plasma(ICP(.