Antibacterial effect of silver nanoparticles deposited on corona‐treated polyester and polyamide fabrics

The possibility of using a corona treatment (electrical discharge at atmospheric pressure) for fiber surface activation, which can facilitate the loading of silver nanoparticles (NPs) from colloids onto the polyester (PES) and polyamide (PA) fabrics and thus improve their antibacterial properties, was studied. Bactericidal efficiency and its laundering durability on silver‐loaded fabrics for Gram‐positive bacterium Staphylococcus aureus and Gram‐negative bacterium Escherichia coli were evaluated. The fiber morphology after corona treatment and subsequent loading of silver NPs was followed by SEM. Corona‐treated fabrics loaded with silver NPs exhibited better antibacterial properties in comparison with untreated fabrics. In order to obtain acceptable laundering durability, it is necessary to use highly concentrated silver colloids. Copyright © 2008 John Wiley & Sons, Ltd.     

Multipurpose nonwoven viscose/polypropylene fabrics: Effect of fabric characteristics on sorption and dielectric properties

In this work, sorption and dielectric properties of viscose/polypropylene multipurpose nonwoven fabrics were examined. The analysis of sorption behavior showed that the changes of the water absorptive capacity, the height of capillary rise and water retention value are in a function of viscose fiber content, total porosity, the pore size and used web bonding process. It is observed that dielectric properties at frequencies from 30 Hz to 140 kHz, for samples exposed to different relative air humidity and wet samples, are dependent on viscose fiber content, web bonding process, frequency of electric field and bulk free water content. The effective dielectric permeability of wet samples rapidly decreases with an increase in frequency up to 3 kHz while spectra of the AC specific electrical conductivity showed a plateau above 13 kHz. It is also observed that the dielectric properties of wet samples increase by several orders of magnitude compared to dry samples. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 947–957     

Review: Antibacterial behavior of carboxylate silver(I) complexes

Since ancient times, silver ions have been known to be effective against a broad range of micro-organisms but in the last decade, this metal has been greatly studied because of their antimicrobial capability against a wide range of bacteria, viruses, and fungi. For the same reason, it is the most extensively studied metal with antibacterial applications in medicine. Besides applications, the antimicrobial activity is associated with high effectiveness, low toxicity, and virtually no resistance of micro-organisms to the presence of this metal. The appearance of new bacterial strains resistant to antibiotics is a serious health problem; so, there is a strong incentive to develop new bactericides. This makes current research in bactericidal silver complexes particularly important. This review summarizes the most important aspect related to coordination chemistry of Ag(I) carboxylate complexes and their influence as antibacterial agents.     

Evaluation of thermal protective performance of basalt fiber nonwoven fabrics

Thermal insulation and fire protection have been a point of interest and discussion for several decades. Due to its excellent performances, basalt fiber has been widely used in the fields of thermal insulation and fire protection. The morphological structure and thermal stability of continuous basalt fiber were analysed using CH-2 projection microscope, scanning electron microscope (SEM) and thermogravimetry (TG). In order to evaluate the thermal radiation protective performance when exposed to fire environment, the spectral reflectances of nonwoven fabrics with different thicknesses were evaluated by ultraviolet-visible-near infrared (UV–Vis–NIR) spectrophotometer analysis. The jointly analysis of TG and UV–Vis–NIR spectrophotometer revealed that the basalt fiber exhibits good thermal stability, and the nonwoven fabrics present excellent thermal protective performance.     

Antibacterial and antioxidant properties of phyto-synthesized silver nanoparticles using Lavandula stoechas extract

Due to environmentally friendly and cost- effective issues, biological methods for silver nanoparticles (AgNPs) synthesis are advantageous over chemical and physical ones. In this study, AgNPs synthesized using Lavandula stoechas extract as a reductant and its antioxidant capacity, antibacterial property and cytotoxicity effect were investigated. The phyto-synthesized AgNPs were characterized using various analyses such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD) as well as Fourier transform infrared (FT-IR). The prepared nanoparticles were spherical on shape with the size about 20–50 nm. Antibacterial studies through agar disk diffusion method confirmed the antibacterial potential of phyto-synthesized AgNPs toward two clinical Staphylococus aureus and Pseudomonas aeruginosa bacteria, although MTT assay demonstrated that S. aureus (MIC = 125 μg/ml) was more susceptible to AgNPs than P. aeruginosa (MIC = 250 μg/ml). Moreover, the cytotoxicity assay of phyto-synthezied AgNPs showed a low cytotoxic effect on RAW264 cell line at 62.5 μg/ml as an effective concentration. Also the considerable antioxidant capacity of the AgNPs confirmed through DPPH assay. Great antibacterial and antioxidant properties along with biocompatibility make the suggested phyto-synthesized AgNPs a great candidate for different biomedical applications including wound healing.     

Dynamic crystallization behavior,morphology, and physical properties of highly concentrated poly(vinylidene fluoride)/silver nanocomposites

The effects of the inclusion of silver (Ag) nanoparticles on the physical properties, the crystallization behavior under shear, and the consequential crystalline morphology of poly(vinylidene fluoride) (PVDF) were investigated. Ag nanoparticles were melt compounded with PVDF in weight fractions of 20, 50, and 90 wt % (15.3 vol %). In the melt rheology, the presence of 20 wt % Ag nanoparticles had little effect on the dynamic viscosity of PVDF, but further addition increased it with the loading level. In Cole–Cole plot, all the melts gave a single master curve independent of the presence of Ag nanoparticles. As Ag loading level was increased, the overall crystallization process under shear was accelerated by reducing both induction time and crystallization time. The degree of acceleration was more notable at higher crystallization temperatures. The induction time and the crystallization time of 90 wt % loaded nanocomposites were promoted by 53.5 and 3.7%, respectively, at 145 °C and by 62 and 26.3%, respectively, at 160 °C, compared with those of pure PVDF. For the isothermal crystallization measured by differential scanning calorimeter, the critical Ag concentration, where overall crystallization was not promoted by further addition, occurred between 50 and 90 wt %. Both wide angle X‐ray diffraction profiles and Fourier transform infrared spectra of the samples crystallized under shear displayed the peaks for only α‐form crystals without new peak or peak shift regardless of the Ag loading and crystallization temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Preparation and properties of silver nanocomposite fabrics with in situ-generated silver nano particles using red sanders powder extract as reducing agent

Nanocomposite cotton fabrics with in situ-generated silver nanoparticles (AgNPs) were prepared by using Pterocarpus santalinus (Red sanders) extract in water as a reducing agent. The formation of AgNPs was analyzed by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy. The SEM analysis of nanocomposites showed the presence of spherical AgNPs with a size range of 71–90?nm. FTIR spectra showed the involvement of hydroxyl and methylene groups of cellulose matrix in reducing the silver salt into AgNPs in the presence of red sanders powder extract as reducing agent for the in situ generation of AgNPs. These nanocomposite fabrics exhibited good antibacterial activity against Gram positive and Gram negative bacteria.     

Antibacterial cotton fabrics with in situ generated silver and copper bimetallic nanoparticles using red sanders powder extract as reducing agent

Using aqueous extraction of red sanders powder as a reducing agent, silver and copper bimetallic nanoparticles were in situ generated in cotton fabrics. Silver and copper nanoparticles were also generated separately for comparison. The resulted nanocomposite cotton fabrics (NCFs) were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and antibacterial tests. SEM analysis indicated the generation of more number of nanoparticles when bimetallic source solutions were used. Further, the size range of the generated bimetallic nanoparticles was found to be lower than when individual metal nanoparticles were generated in NCFs. XRD analysis confirmed the in situ generation of silver and copper nanoparticles when equimolar bimetallic salt source solutions were utilized. The NCFs with bimetallic nanoparticles exhibited higher antibacterial activity against both Gram-negative and Gram-positive bacteria and hence can be considered for applications as antibacterial bed and dressing materials.     

Antibacterial properties of novel poly(methyl methacrylate) nanofiber containing silver nanoparticles

Poly(methyl methacrylate) (PMMA) nanofiber containing silver nanoparticles was synthesized by radical-mediated dispersion polymerization and applied to an antibacterial agent. UV-vis spectroscopic analysis indicated that the silver nanoparticles were continually released from the polymer nanofiber in aqueous solution. The antibacterial properties of silver/PMMA nanofiber against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria were evaluated using minimum inhibitory concentration (MIC), the modified Kirby-Bauer method, and a kinetic test. The MIC test demonstrated that the silver/PMMA nanofiber had enhanced antimicrobial efficacy compared to that of silver sulfadiazine and silver nitrate at the same silver concentration.     

Optical and thermal properties of Fe3O4 nanoparticle-doped cholesteric liquid crystals

A composite system of Fe₃O₄ nanoparticle-doped cholesteric liquid crystals with properties of broadband reflection and controllable temperature under high-frequency electric field is proposed. The broadband reflection can shield the near-infrared light in summer and the electromagnetic-thermal effect by the Fe₃O₄ nanoparticles can deice or defrost in winter for high transmittance and good safety. Furthermore, the thermal effect may be precisely controlled and significantly enhanced by adjusting the factors of the doped concentrations and the applied electric field parameters (duration time, magnitude and frequency). This composite system may have potential applications for multifunctional windows of architectures and vehicles.     

Megaporous monolithic adsorbents for bioproduct recovery as prepared on the basis of nonwoven fabrics

Megaporous adsorbents were prepared based on nonwoven polyethylene terephthalate (PET) fabrics and functionalized by covalent modification with polyvinylamine (PVAm) or monotriazinyl-β-cyclodextrin-substituted polyvinylamine (PVAm-MCT-β-CD). Mechanical properties of the resulting fabrics were maintained, as judged by tensile strength tests and scanning electron microscopy. Exceptional porosity (≥82%) and preserved hydrodynamic characteristics (Pe ≥ 63) indicated excellent structural stability when packed. The performance of the constructed adsorbents was evaluated with high molecular weight (proteins) and low molecular weight (dyes) model compounds. The static binding capacity (SBC) for bovine serum albumin (BSA) was 79.7 ± 1.3 and 92.9 ± 8.2 mg/g for PVAm-modified and PVAm-MCT-β-CD-modified fabrics, respectively. The mentioned materials also adsorbed Orange II, an acidic dye (92.4 ± 2.6 and 101.9 ± 2.6 mg/g, respectively), indicating that the hydrophobicity was a prevailing binding mechanism operating at a pH close to isoelectric point. SBC for lysozyme and toluidine blue O (TBO, a basic dye) onto PVAm-MCT-β-CD functionalized PET was 52.7 ± 5.1 and 73.3 ± 0.6 mg/g, respectively. TBOs have also shown some affinity for PVAm functionalized PET, but this was most likely to be mediated by hydrophobicity. On the other hand, operating at a superficial velocity of 90 cm/h, dynamic binding capacity for BSA was 11.4 ± 3.5 and 2.5 ± 0.6 mg/g indicating the importance of possible aggregation mechanisms during protein binding at equilibrium. Thus, PET-based adsorbents require further functional improvement for chromatography applications. However, the easy-to-construct, scalable nonwoven adsorbents deserve further attention as a potential alternative to packed-bed-chromatography adsorbents.     

Experimental investigation on the thermal protective performance of nonwoven fabrics made of high-performance fibers

In this study, the thermal protective performance of nonwoven fabrics made of Nomex (polyisophthaloyl metaphenylene diamine), PPS (polyphenylene sulfide), P84 (polyimide), and basalt fibers was investigated. The objective was to determine the influence of fiber type, thickness of fabric, and wet on the thermal protective performance of nonwoven fabric. The thermal resistances of different nonwoven fabrics were measured using a dry hot plate instrument, the basalt nonwoven fabrics had a highest thermal resistance in all fabric, and the thermal resistance of nonwoven fabric increased with the increase in thickness. The six nonwoven fabrics were exposed to a hot environment for a few minutes by using a self-designed apparatus. The test results showed that the nonwoven fabrics made with basalt fiber exhibited the best thermal protective performance, and the thermal protective abilities of nonwoven fabrics increased with fabric thickness. Interestingly, nonwoven fabrics with added water were found to be able to keep the fabric surface lower temperature compared to dry fabrics when exposed to a hot environment, indicating the excellent thermal protective performance of wet nonwoven fabrics.     

Foaming behavior,cellular structure and physical properties of polybenzoxazine foams

In this paper, polymer foams based on a benzoxazine resin have been successfully prepared using azodicarbonamide (ADC) as a chemical blowing agent and have been characterized regarding their foaming behavior, cellular structure, and physical properties. The effect of the ADC on the curing process of the resin was analyzed using differential scanning calorimetry and blowing agent decomposition was followed by thermogravitmetric analysis (TGA). The characterization of the cellular structure of the foamed samples was done using scanning electron microscopy. The mechanical properties of the foams were determined using compression tests and the thermal conductivity was assessed using the transient plane source method. The results indicated that the curing process and gas release took place in a similar time interval. The foams showed an isotropic cellular structure with relative densities in the range 0.35–0.60, and showed compressive strengths and compressive moduli in the range of 10–70 MPa and 400–1100 MPa, respectively. Thermal conductivities were in the range of 0.06–0.12 W m^?1K^?1. The findings in this paper demonstrate the possibility of producing polybenzoxazine foams using a simple process in which curing and foaming take place simultaneously. In addition, the mechanical characterization of these materials indicates that they are suitable for structural applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermal properties of textile fabrics

Objective evaluation techniques were used in this study of thermal properties of textile fabric. The Alambeta, P tester, and Togmeter measure the passages of air which were used for evaluation of the physiological properties. Fibrous materials were prepared in the form of textile knitting fabric COOLMAX. It is clear from the measurement that there are considerable differences in the results of measurement with described methods. Device Alambeta is convenient for the measurement and evaluation of various thermal properties. Finally, it can be concluded that this field of measurements is developing and will be the subject of further research of other methods, more suitable for measurement of the various characteristics.     

Preparation of Antibacterial Waterborne Polyurethane/silver Nanocomposite

Stable aqueous dispersions of silver (Ag) nanoparticles were prepared by reducing silver nitrate solutions with sodium borohydride (NaBH₄) in the presence of waterborne polyurethane as a stabilizing agent. WPU/Ag nanocomposites were obtained after evaporating water. Transmission electron microscope (TEM) shows nanoscale Ag particles are well dispersed in WPU matrix at a lower concentration, while particles exhibit a little aggregation at a higher concentration. UV‐visible spectra, X‐ray powder diffraction, and energy dispersive X‐ray spectrometer (EDS) confirm the existence of Ag particle in WPU matrix. The WPU/Ag composite films show good antibiotic ability.     

Transport properties of electrospun nylon 6 nonwoven mats

In this work, we evaluate the physical properties of nylon 6 nonwoven mats produced from solutions with formic acid. Nonwoven electrospun mats from various solutions with different concentration are examined regarding their morphology, pore size, surface area, and gas transport properties. Each nonwoven mat with average fiber diameters from 90 to 500 nm was prepared under controlled electrospinning process parameters. From the results, it was observed that the fiber diameter was strongly affected by the polymer concentration (polymer viscosity). In additional the results showed that the pore size, Brunauer-Emmett-Teller (BET) surface area, and gas transport property of electrospun nylon 6 nonwoven mats were affected by the fiber diameter.     

Morphology and physical properties of a novel Ramie‐PU blended nonwoven by electrospinning: The effect of cosolvent ratio

A novel macro/nano blended nonwoven with excellent physical properties was prepared by electrospinning polyurethane (PU) nanofibers onto the surface of ramie webs under different weight ratios of N,N‐dimethylacetamide (DMAc)/acetone cosolvents. The ratio of cosolvents has a significant influence on the morphology, tensile properties, resilience, and thermal properties of the resultant samples. Bead‐free and fine interconnected nanofibers were obtained with an increase of acetone content up to 60 wt%. The total physical properties of the blended nonwovens were optimal for a DMAc/acetone ratio of 40/60, in which the tensile load at break, extension at break and Young's modulus were 441, 54, and 256% higher than that of pure ramie web, respectively. The resilience of the blended nonwovens was ～20% higher than that of nonblended ramie web. The significant improvement of physical properties may be due to the good connection between PU nanofiber membranes and ramie webs and the molecular chain structure differences, interconnected structural differences, and high extensibility of PU nanofibers, according to the results of crystallization by differential scanning calorimetry (DSC) and morphological observation by scanning electronic microscopy (SEM). © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1–14, 2010     

CI Reactive Black 5 dye as a visible crosslinker to improve physical properties of lyocell fabrics

Bi-functional reactive dyes have been used for reducing the fibrillation of lyocell fibres. The sole influence of CI Reactive Black 5 dye on the fibrillation tendency of lyocell single jersey knitted fabrics was investigated by dyeing with different concentrations (35 g/L for medium shade and 70 g/L for dark shade), dyeing without dyestuff and by decolouration process after each dyeing. The fibrillation tendency of lyocell fibres was accessed by means of fibre wet abrasion resistance and fibrillation number. Nitrogen content was used as indication of the amount of reactive dye in fabrics during dyeing and decolouration processes. The correlation between fibre fibrillation tendency and colour values of fabrics was found. Due to the fibrillation reduction, pilling formation in dyed lyocell fabrics was improved. As colour values can estimate the dye fixation and reduction in fabrics, reactive dye can be used as a visible marker for crosslinking effect on lyocell fabrics.     

Phase behavior and some calorimetric and physical properties of diurethanes from perfluoropolyether macromonomers

Density and calorimetric measurements have been carried out on copolymeric perfluoropolyethers of molecular weight ranging between 500 and 4700, terminated at both chain ends either with  CH₂OH or ethylurethane groups. Samples of the second series are models for perfluoropolyethers based polyurethanes. Density measurements point out that the terminal alcoholic group brings about a negative excess volume, which increases with decreasing the molecular weight; a lower excess volume is found for urethane‐terminated molecules. Calorimetric traces, T_g, and Δc_p at T_g show that alcoholic‐terminated molecules are amorphous and one phase systems, while urethane‐terminated compounds are crystalline; phase separation is observed for this last series when the molecular weight of the fluorinated segment is larger than 1000. The trend of T_g with molecular weight is discussed for one‐ and two‐phase systems in the light of current theories for the glass transition. The decrease of the melting point with increasing the molecular weight for the urethane series can be described by the Flory equation for random copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1609–1622, 1999     

Unified scaling behavior of physical properties of clays in alcohol solutions

This paper reports observation of universal scaling of physical properties of clay particles, Laponite (aspect ratio=30) (L) and Na Montmorillonite (MMT, aspect ratio=200), in aqueous alcohol solutions (methanol, ethanol and 1-propanol) with solvent polarity, defined through reaction field factor f(OH)(?(0),n)=[(?(0) - 1/?(0) + 2) - (n(2) - 1/n(2) + 2)], at room temperature (20°C). Here, ?(0) and n are the static dielectric constant and refractive index of the solvent concerned. Physical properties (Z) such as zeta potential, effective aggregate size, viscosity and surface tension scaled with the relative solvent polarity as Z～δf(α); δf=(f(w)(?(0),n) - f(OH)(?(0),n)), where f(w)(?(0),n) is the reaction field factor for water, Z is the normalized physical property, and α is its characteristic scaling exponent. The value of this exponent was found to be invariant of aspect ratio of the clay but dependent on the solvent polarity only.