Ismail Usta

Electromagnetic shielding effectiveness of polyester fabrics with polyaniline deposition

In this study, conductive fabrics were developed by polymerizing aniline onto polyester (PET) woven fabrics. The fabric treatment was carried out by the chemical polymerization method at 0.5 M, 0.8 M and 1.2 M aniline concentrations. Hydrochloric acid as acidic medium and ammonium persulfate as oxidant were employed during the polymerization process. The polyaniline (PANI)-treated PET fabric structures were fully characterized and evaluated in terms of their electromagnetic shielding effectiveness, absorption and reflection characteristics, and tensile properties. Additionally, the fabrics were examined by scanning electron microscopy for their surface morphology and Fourier transform infrared spectroscopy for their chemical functionality. The electromagnetic shielding effectiveness and absorption and reflection characteristics were determined using a network analyzer with a frequency range from 15 MHz to 3000 MHz. The electrical characteristics were measured by the two-end method. It was concluded that the tensile strength values of the treated fabrics were enhanced when the amount of monomer in the concentrations increased as compared to the untreated fabrics. It is interesting to note that 1.2 M treated fabric had the lowest tensile strength values as compared to the other treated fabrics. It was also found that a 0.5 M concentration of PANI-treated fabric had the lowest surface resistivity since it showed the highest conductivity value. Another important finding is that the 0.8 M aniline-treated fabric had the highest shielding effectiveness.

Electrical properties and electromagnetic shielding effectiveness of polyester yarns with polypyrrole deposition

Polypyrrole was deposited on polyester yarns by vapour phase polymerization technique. Ferric chloride was used as an initiator. In order to determine the effect of the initiator concentration on polymerization process, four different initiator concentrations (0.2, 0.4, 0.6 and 0.8 mol/l) were used. The effect of the initiator in terms of tensile properties, electrical resistivities and morphological properties of the yarns was investigated. The polypyrrole deposited polyester yarns were then weaved in a handloom to form fabric for the investigation of surface resistivity and electromagnetic shielding effectiveness. Scanning electron microscopy, energy dispersive spectroscopy and Fourier transform infrared analyses illustrated that polypyrrole has penetrated into the yarn structure and the highest polypyrrole deposition was obtained at the initiator concentration of 0.6 mol/l. Also, the highest electromagnetic shielding effectiveness value and the lowest surface resistivity were obtained at this concentration.

Investigation of electromagnetic shielding properties of needle-punched nonwoven fabrics with stainless steel and polyester fiber:

In this study, electromagnetic shielding properties of needle-punched nonwoven fabrics were investigated. The paper evaluates and compares the electromagnetic shielding of needle-punched nonwoven fabrics produced from stainless steel/polyester and normal polyester fibers. Stainless steel/polyester fiber and normal polyester fiber were blended at specified ratios in the experimental study. Webs were produced from the fibers with the carding machine and then bonded with the needle-punching machines. The thickness and electromagnetic shielding properties of the needle-punched fabrics were tested. An electromagnetic shielding effectiveness (EMSE) device was used for measuring the electromagnetic shielding. The experimental study indicated that as the conductive stainless steel fiber ratio in nonwoven fabrics increases, the EMSE also increases at low, medium and high frequencies. Satisfactory electromagnetic shielding values were obtained at wide bandwidth, i.e. 1200–3000 MHz. The highest EMSE values of the needle-punched nonwoven fabric with 25% conductive steel fiber were, respectively, 6 dB at 0–300 MHz low frequency, 12 dB at 300–1200 MHz medium frequency and 18 dB at 1200–3000 MHz high frequency. It was found that 90% of electromagnetic waves were shielded by nonwoven fabric at high frequencies, 85% at medium frequencies and 80% at low frequencies.

Properties of Polypropylene Composite Produced with Silk and Cotton Fiber Waste as Reinforcement

The importance of polymer composites among industrial materials is due to their improved mechanical properties. In recent researches, mechanical and physical properties have been improved by way of making composites with fiber reinforcement. Silk and cotton fibers used in the textile industry have good physical and mechanical properties. In this study, composite structures were produced by using recycled Poly Propylene, PP, polymer with silk and cotton waste as fiber reinforcement in different ratios. The fiber dimensions of silk and cotton wastes were between 1 mm, 2.5 mm, and 5 mm. They were mixed in the ratios of PP/silk and cotton waste 97%/3 and 94%/6. The mixture of polymer composite was prepared with double screw extruder. The sample was tested for tensile strength, elongation, yield strength, elasticity modulus, izod impact strength, melt flow index (MFI), heat deflection temperature (HDT), and vicat softening temperature. Thermal transitions of the materials were determined with Differential Scanning Calorimeter (DSC) and micro-structure properties were observed with a Scanning Electron Microscope (SEM).

Synthesis and characterization of dual-curable epoxyacrylates for polyester cord/rubber applications

In this study, bisphenol-A-based acrylated epoxy oligomers were prepared and utilized to improve the adhesion strength of polyester cords onto rubber. The structure of the oligomers was characterized by Fourier transform infrared spectroscopy and 1H-NMR spectroscopy. Ultraviolet-curable adhesive formulations were prepared by using acrylated epoxy oligomers and applied onto the polyester cord fabric by a dip-coating method and irradiated. Ultraviolet-cured coatings were characterized by thermal and scanning electron microscope analysis, contact angle measurements. In the second stage of the experiment, ultraviolet-cured polyester cords were adhered onto rubber under heat and pressure. The prepared adhesive formulation was expected to improve the adhesion strength. The adhesion strength of the coated material was evaluated by using peel test as a function of the carboxyl/epoxide ratio. The adhesion strength of 18.0 N/cm was obtained when the carboxyl/epoxide ratio was set as 1. It was observed that peel strength, contact angle, and surface energy values of acrylated epoxies strongly depend on the acrylic acid content of the oligomer.

Development and characterisation of polyaniline/polyamide (PANI/PA) fabrics for electromagnetic shielding

In this study, novel conductive fabrics were developed by polymerising of aniline onto the polyamide (PA)-knitted fabrics. The fabric treatment was done by the chemical polymerisation method at 0.5, 0.8 and 1.2 M aniline concentrations. Hydrochloric acid as acidic medium and ammonium per sulphate as oxidant were employed during the polymerisation process. The polyaniline (PANI)-treated PA fabric structures were fully characterised and evaluated in terms of their electromagnetic shielding effectiveness, absorption and reflection characteristics and tensile properties. Additionally, the fabrics were examined by scanning electron microscope (SEM) for the surface morphology and Fourier transform infrared spectroscopy for the chemical functionality. The electromagnetic shielding effectiveness, absorption and reflection characteristics were determined by Network Analyzer with a frequency ranged from 15 to 3000 MHz. The electrical characteristics were measured by the two ends method. It has been concluded that the bursting strength values of the treated fabrics reduced when the amount of monomer in the concentrations decreased as compared to the untreated fabrics. It is interesting to note that 1.2 M treated fabric had the highest bursting strength values as compared to the other treated fabrics. It was also found that 0.5 M concentration of PANI-treated fabric had the lowest surface resistivity due to this it showed the highest conductivity value. Another important finding is that the 0.5 M-aniline treated fabric had the highest shielding effectiveness.

The effect of multiwalled carbon nanotube (MWCNT) ratio on electrical properties and electromagnetic shielding effectiveness of PA 6/MWCNT-coated cotton fabrics

Polyamide 6 (PA 6)/multiwalled carbon nanotube (MWCNT)-coated cotton fabrics having varying amounts of MWCNTs (10, 12, 14 and 16 wt.%) in PA 6 (10, 15 and 20 wt.%) were fabricated with dip coating method to investigate the electromagnetic shielding properties in the frequency range of 15–3000 MHz. The effects of MWCNT loading on electrical resistivity, electromagnetic interference shielding effectiveness and also shielding mechanism have been studied. The highest electromagnetic shielding effectiveness value was obtained at 20 wt.% MWCNT loading in 10 wt.% PA 6 and the PA 6/MWCNT-coated composites showed the absoprtion-dominated shielding mechanism.

Electromagnetic shielding and electrical properties of polyurethane acrylate/E-glass composites in the 3–13 GHz frequency range

The electromagnetic shielding effectiveness (EMSE) and surface resistivity of UV-cured polyurethane acrylate (PUA) / copper wire / E-glass fabric composites in the frequency range of 3–13 GHz were investigated using a free space measurement. The effect of polyvinyl butyral (PVB) binder on the shielding and electrical properties were searched by using a range of PVB concentrations 2.5, 5, 7.5 % and without PVB. The best EMSE value of 25 dB was obtained in the frequency range of 5–9 GHz by adding 2.5 % PVB. When the addition of PVB was more than 2.5 %, the shielding effect decreased. The sample which contains 2.5 % PVB was showed the least surface resistivity and the best EMSE value.

Investigation of the Filtration Properties of Medical Masks

ABSTRACT Medical masks are mostly produced from textiles. Weaving, knitting and nonwoven technologies are used to produce masks. But, nowadays, nonwoven technology is preferred for the mask production method. Nonwoven surfaces has good filtration properties. Mostly polyester and polypropylene fibers are used for mask production. Medical masks are designed to enable different functions. Generally masks have to protect from virus, bacterias, biological substances and particules in the air. Medical masks enable all these properties and produced according to application field. This is the first and initial results of the medical filtration project carried out by the authors. In this study particule filtration properties of different masks have been investigated. For each mask smallest particule size filtrated from the air accepted as the base for the comparison.

The Effects of Fabric and Conductive Wire Properties on Electromagnetic Shielding Effectiveness and Surface Resistivity of Interlock Knitted Fabrics

Our aim in this study was to investigate the effects of course density, yarn linear density and thickness and type of conductive wire on electromagnetic shielding effectiveness. Metal/cotton conductive composite yarns were produced by the core-spun technique on the ring spinning machine, involving stainless steel, copper and silver coated copper wires with 40 μm, 50 μm, 60 μm thicknesses and Ne10/1 and Ne20/1 count yarns. The interlock fabrics were knitted on a 7G flat knitting machine with the three different machine settings. The EMSE and the surface resistivity of knitted fabrics were measured by the co-axial transmission line method according to the ASTM-D4935-10 standard in the frequency range from 15 to 3000 MHz and by the ASTM D257-07 standard, respectively. It was observed that all fabrics shielded around 95 % of electromagnetic waves at low frequencies, 80 % at medium frequencies and 70 % at high frequencies. Increasing the course density and thickness of conductive wire in interlock knitted fabrics increased the EMSE correspondingly. The knitted fabrics that had been produced with high yarn count showed greater EMSE because there was less isolation. The effect of the metal wire type was highly significant between 15 and 600 MHz.