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Abstract (English):
Despite technological progress, the corrosion phenomenon has caused many problems and dangers, which are possible to control and decrease by coating metal surfaces and reducing their contact with the environment. The article presents the results of a research, where graphene is used as a key matter due to its unique characteristics: mechanical, electrical, anti-bacterial, flexibility and high resistance to chemicals. Polyester is also used for its good elastic properties, high strength, and water repellency. In the course of the study nonwoven polyester was coated with resin and graphene powder of different percentage and different thickness. Then, the iron was coated with the prepared composite, and finally, the prepared samples were examined for corrosion, fabric strength, anti-bacterial properties and fabric resistance against water penetration. The results show that the effective coating greatly improves the sample parameters. According to analysis of the tests results, the presence of resin with graphene improves properties of polyester. The composite tested is recommended to use as an antibacterial coating material against corrosion for industrial needs.

graphene, corrosion, anti-bacterial properties, nonwoven polyester
Introduction Nonwoven textiles have the same structure as fabric; however, they are not woven by entangling threads, rather they are sprayed onto a fabric like surface in various fiber processes directly, so they are called nonwoven textiles [1]. Generally, nonwoven tissue is not highly strengthened and it is produced in a form of a web or a block of short length fibers, in which fibers are parallel or straight forward. These textiles can be changed into a layer of woven wrap knitted, weft knitted, weft and wrap knitted by means of friction force, resin, wet process or needle felting without forming threads or fibers knots. Polyester is a category of polymers that contain the ester functional group in their main chain usually formed by polymerizing a polyhydric alcohol with a polybasic acid, which reaction of alcohol with carboxylic acid results in the formation of esters [1]. In polymer and textile industries, polyester fibers refer to fibers produced from polyethylene terephthalate (polyethylene and Dacron) that are the most common types. Corrosion in Persian means chewed. Corrosion is a spontaneous phenomenon that all the people encounter with in their daily lives from the discovery of metal. The main reaction of corrosion is the oxidation of metal from the zero oxidation degree to the highest degrees [2]. According to ISO 8044, corrosion is a destructive physical-chemical reaction between metal and an environment that usually is electrochemical in nature resulting a change in metal or material properties. These changes may cause the metal, environment, or device deficiency. Due to the fact that thermodynamically oxidized materials have lower energy levels than in their normal state, the intention to reach lower energy causes metal corrosion [2]. Unfortunately, as a result of enormous damage, corrosion could never be prevented, but by choosing suitable amalgam, employing corrosion prohibition, cathode and anode protection and using resistant coating (coating and polishing), it can be minimized. According to XRD results, carbon atoms set layers of graphene as a honeycomb lattice between graphite layers. Graphene is made up of a flat monolayer of Sp2-hybridized carbon atoms. Despite the very short life of graphene invention, it is known as a pioneer in nanotechnology and it can be easily combined with polymers because of different functional groups [3]. On the other hand, due to its different functional groups, which can be easily combined with various polymers, the high productivity and low cost of raw material, it is considered as a replacement for organic and other inorganic fillers, so it is known as a magic substance of the 21-st century [4]. One of the properties of graphene is its capability to protect metal from the corrosive environment such as sea water and salty condition [5]. According to the previous studies, graphene acts as a strong barrier against penetration of destructive ions, which finally improves metal resistance to oxidation in corrosive environments [6]. In this study nonwoven polyester was coated with resin and different percent of graphene powder of different thickness, and which the iron was coated by the prepared composite. According to nonwoven textile production method, there has been space between fibers which was filled with resin and graphene during the coating of nonwoven polyester resulting in increase and improvement of corrosion characteristics, strength and other properties of graphene coated textile. Finally, prepared samples were examined for presence of corrosion, fabric strength, fabric resistance against water penetration and anti-bacterial properties. Experimental section Materials. In this study, materials were prepared, according data given in Тable 1. Table 1 Technical specification of materials Producer name Technical properties Name Row American Supermarket Company With a molecular weight of 60 nm Nano-graphene powder 1 Tehran Spun Bund Company With a molecular weight of 45 g/m2 and width of 35 mm Non-woven Polyester 2 Negin Industrial of Ziba Shahr Company Based on Vinyl acetate copolymer Resin (Shining Crystal Coating) 3 Germany, Merck Company With 99.5% of purity CH2CO2H Carboxyl methyl cellulose (CMC) 4 Germany, Merck Company 99.8% purity Sulfuric acid (H2SO4) 5 Germany, Merck Company 99% purity Sodium Hydroxide (NaOH) 6 Marine Chemicals Company - Silicone defoamer 7 Sample Preparation. In this research, weight percent and thickness of graphene were optimized. Graphene weight percent made 0.02, 0.04, 0.08, and 0.16 and the optimized thicknesses were 50, 100, 150, 200, 400 and 1 mm. Next, graphene powder, resin, carboxyl methyl cellulose powder and defoamer were mixed well by mechanical mixer with rotational speed of 2600 rpm. After calibration of film stretcher machine, non-woven polyester was set to a desired size and a few drops of coating solution (of desired thicknesses) were dropped on non-woven polyester by the emitter, then a smooth surface was created by a suitable blade on the non-woven polyester. Experiment Method Potentiostat - Galvanostats test (anti corrosion). For analyzing corrosive characteristics, the Potentiostat-Galvanostats instrument of Compact state model, made in Netherland and electrochemical spectrometer with constant potential were used. To search for samples’ electrochemical properties, in a glass vial three electrodes were utilized including the auxiliary electrode or counter electrode made of platinum and Ag /AgCl electrode as the reference electrode. There were employed coated samples with a surface area of 1 cm2 as the working electrode, in the range of potential 0/2-1 V frequency Hz 100000-01 / 0 immediately immersed in a solution and after attaining fixed potential for curve analysis and corrosion rate. To determine metal corrosion rate and corrosion current the following equation was used based on Faraday law: In this equation Rm is corrosion rate, M is metal atomic mass; n is the number of transferred electrons during corrosion process; F is Faraday constant (96.458 C.mol); ρ is density; and icorr is corrosion current. Metal corrosion rate depends on cathode and anode process rate, when the external current applied, cathode and anode rate change so that the difference between them equals to the external current; therefore, metal potential differs from condition without the external current. Accordingly, if we have external currents in constant potential, information of cathode and anode reactions can be obtained. Antibacterial Test. In order to analyze and evaluate antibacterial properties the AATCC100-1993 method was used. Based on standard conditions, the bacterial density should be 1-2 × 105 (microorganism indicator). In this study, S. Aureus )Staphylococcus Aureus) bacteria with ATCC25932 specification was investigated as a gram-positive bacteria and E. Coli )Coli Escherichia) with ATCC25932 specification was utilized as a gram-negative bacteria. The following formula was used for obtaining antibacterial potential: In this equation, A indicates a control sample and B indicates experimental samples. In order to determine inoculation degree, a completed microbial loop from 24 hours cultivated microorganism was diluted with physiological serum (McFarland standards), which has 0.009 g/l salt and 20 ml of Nutrient Broth was added as a liquid medium in the first stage. After 5 hours of heating at 37ºC and 150 RPM, 250 mcl of that were utilized for inoculation of 50 ml nutrient media as a final cultivating. At intervals of zero, one, two and three hours absorbance suspension of microorganisms in the culture medium at a wavelength of 600 nm was spectrometrically quantified and viable count was performed based on Plate Count Method. Accordingly, optical absorption at 0.005 of appropriate cell densities (1-2 × 105) was used for both bacterial indicators. Strength Measurement Test. The strength of samples was measured by M50-25 Testometric at standard condition ASTM D5035. For tensile strength of each sample, 5 samples of 6 × 30 cm at 20 cm distance between jaws were tested. Water Penetration Resistance Test. Water penetration resistance of samples was measured based on AATCC 39 standard. A burette was set at a distance of 6 mm above the horizontal plane of samples containing distilled water, it was given time until a drop of water falls and spreads. A fabric which was lit at 45°C, was seen in the opposite direction and when the liquid diffusive reflection faded, no liquid was seen and the timer stopped. Results and Discussion Corrosion test results. The results of corrosion changes for samples finished with graphene without nonwoven polyester are shown in Table 2, and the results of corrosion changes for samples finished with graphene and nonwoven polyester are shown in Table 3. Table 2 The results of corrosion changes for samples finished with graphene without nonwoven polyester Index Parameter A B C D a b a b a b Current icorr (µA) 2 48 68 36 59 19 15 Potential Ecorr (V) -0/11 -2/78 -3/94 -2/08 -3/42 -1/1 -0/87 Corrosion Rate Rm(µA) 0/072 1/36 2/44 1/29 2/12 0/68 0/54 Table 3 The results of corrosion changes for samples finished with graphene and nonwoven polyester Index Parameter A B C D a b a b a b Current icorr (µA) 2 48 52 21 42 11 8 Potential Ecorr (V) -0/11 -2/78 -3/01 -1/21 -2/43 -0/63 -0/46 Corrosion Rate Rm(µA) 0/072 0/63 0/97 0/51 0/77 0/36 0/44 A: Control Sample. B: Sample with 50 micron width: a: sample with 0.02% Graphen; b: sample with 0.16% Graphen. C: Sample with 150 micron width: a: sample with 0.02% Graphen; b: sample with 0.16% Graphen. D: Sample with 400 micron width: a: sample with 0.02% Graphen; b: sample with 0.16% Graphen. Samples with Graphene and nonwoven polyester (Fig. 1) are more resistant to corrosion. Fig. 1. Electron microscopic image of the nonwoven polyester layer coated with graphene As a result of increasing graphene thickness in coating, graphene layer improves nonwoven coated polyester and boosts corrosion resistance of samples, as this layer functions like a dam (Fig. 2) that increases the influence of corrosive ions into coating area reaching to metal surface, leads to reducing the corrosion rate and can also provide the cathode protection of steel. Fig. 2. Electron microscopic image of created dam or corrosive ion barrier Antibacterial Test Results. Results of strength test for graphene coated nonwoven polyester are shown in Table 4. According to the results of coated samples, when thickness and amount of graphene increase, antibacterial protection enhances due to antimicrobial activity in graphene. Table 4 Antibacterial Test Result Sample’s thickness A B C Before Fastness Test After Fastness Test Before Fastness Test After Fastness Test After Fastness Test Before Fastness Test 0.02 5/52 1/85 9/29 4/56 8/22 51/7 9/56 6/90 6/40 2/59 5/26 56/8 0.04 4/76 7/95 3/53 7/75 9/45 6/65 6/79 2/96 4/56 8/78 4/49 9/65 0.16 9/86 6/97 7/70 7/91 6/62 6/77 5/89 4/98 5/73 1/92 9/64 7/79 A: Sample with 50 Micron Width; B: Sample with 150 Micron Width; C: Sample with 400 Micron Width. Strength Test Results. Samples’ strength was tested in three states. The results for graphene coated nonwoven polyester in 150 Micron (least width) is shown in Table 5. As it can be observed, by adding graphene, the graphene layer improves nonwoven polyester, which leads to reduction in tensile strength and increase in elongation at break, which in conclusion enhances strength of samples coated with graphene. Table 5 Samples strength changes results in 150 Micron thickness Index Parameter A B C a b a b a b Breaking strength, kgf 99/23 53/27 03/22 64/26 48/21 45/25 Elongation at breakage, mm 80/61 22/56 47/23 03/21 59/48 51/49 The strength test results for coated nonwoven polyester with graphen in 1 mm (maximum thickness) are shown in Table 6. As it can be observed, by adding more graphen, the graphen layer improves nonwovwn polyester resulting in decrease in breking strength and increase in elongation tenacity. It can be concluded that, increase in graphen enhance strength of graphen coated samles. Table 6 Samples strength changes results in 1mm thickness Index Parameter A B C a b a b a b Breaking strength, kgf 69/26 99/27 62/21 31/24 26/26 93/23 Elongation at breakage, mm 13/62 38/58 31/136 04/135 84/105 61/149 A: samples were not soaked in acid and alkaline solution: a: sample with 0.02% of graphene; b: sample with 0.16% of grapheme. B: The samples laid in acid solution (H2SO4) with a purity of 98%: a: sample with 0.02% of graphene; b: sample with 0.16% of grapheme. C: Samples are placed in alkaline solution (NaOH) with a purity of 99%. Finally, it can be inferred that with increasing graphene percentage and graphene layer thickness, crystalline regions of graphene grow, which results in improving the strength of nonwoven polyester. Water Penetration Resistance Test Results. The results of water penetration resistance test for graphene coated nonwoven polyester are shown in Fig. 3. The absorption time of a drop of water for the control sample (nonwoven polyester) before treatment is 9.4 minutes, which reduces to 1.56 minutes after treatment. Fig. 3. Water Penetration Resistance Test Results Before the treatment, by increasing the thickness of the samples with graphene and forming a layer on the textile, the absorption time of a drop of water increased as well. After finishing process, the absorption time of a drop of water reduced compared to graphene coated samples before the finishing process. It can be concluded that the absorption time of a drop of water decreased after finishing by increasing graphen thickness layer. Conclusion The aim of this study was to protect the metal items from corrosion in different conditions, to improve the quality of composites and coated materials with addition of graphene of various percentages and thicknesses. The results of the analyses of corrosion, the antibacterial tests, tests of fabric strength and fabric resistance against water penetration have been studied. Reported tests results proved that the use of graphene in nonwoven polyester, which has been finished based on graphene, can protect corrosion to a large extent. According to the evaluation of the results, it can be inferred that polyester fabric coated with graphene is a means of protection against corrosion and anti-microbial proof recommended for industrial application. Although many reports about graphene coated metals such as nickel, copper and steel have been proposed, which improves corrosion of metals in corrosive environments, the research on graphene-based nonwoven polyester has not been done yet.

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