Electrospun nylon 6 nanofibers incorporated with 2‐substituted N‐alkylimidazoles and their silver(I) complexes for antibacterial applications

The article presents the incorporation of biocides [2‐substituted N‐alkylimidazoles and their silver(I) complexes] into electrospun nylon 6 nanofibers for application as antimicrobial materials. The electrospun nylon 6/biocides nanofiber composites were characterized by IR spectroscopy (ATR‐FTIR) and scanning electron microscopy (SEM‐EDX). The antimicrobial activity of the electrospun nylon 6/biocides nanofiber composites was evaluated against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis subsp. spizizenii using the disk diffusion method, the American Association for Textile Chemists and Colorists test method 100‐2004 and the dynamic shake flask method (American Society for Testing and Materials E2149‐10). The electrospun nylon 6 nanofibers incorporated with 2‐substituted N‐alkylimidazoles displayed moderate to excellent levels of growth reduction against S. aureus (73.2–99.8%). For the electrospun nylon 6 nanofibers incorporated with silver(I) complexes, the levels of growth reduction were >99.99%, for both E. coli and S. aureus, after the antimicrobial activity evaluation using the shake flask method. The study demonstrated that the electrospun nanofibers, fabricated using the incorporation strategy, have the potential to be used as attractive antimicrobial materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39783.     

Fabrication and Antibacterial Activity of Electrospun Nylon 6 Nanofibers Grafted With 2-Substituted Vinylimidazoles

The authors present the fabrication of electrospun nanofibers with antimicrobial properties by the UV-initiated grafting (photo-grafting) of 2-substituted vinylimidazoles onto nylon 6 nanofibers. The characterization was performed using IR spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM-EDX). The antimicrobial properties of the grafted electrospun nylon 6 nanofibers were evaluated against Escherichia coli and Staphylococcus aureus as model challenge microorganisms, using the dynamic shake flask method. All the grafted electrospun nylon 6 nanofibers exhibited excellent growth reduction of E. coli (99.94–99.99%) and S. aureus (99.55–99.99%). The electrospun nylon 6 nanofiber composites could be used twice before a decrease in antibacterial activity was observed. The study showed that electrospun nylon 6 nanofiber composites possess a potential for use to control pathogens in water.     

Antimicrobial activity of organic photosensitizers embedded in electrospun nylon 6 nanofibers

Nylon 6 nanofibers containing organic photosensitizers were investigated to demonstrate the antimicrobial properties in the application of the material to protective clothing and home appliances. Benzophenone (BP), 4, 4′‐bis(dimethylamino)benzophenone (MK) and thioxanthen‐9‐one (TX) were used as photosensitizers and the nylon 6 nanofibers were prepared using electrospinning. Field emission scanning electron microscopy morphology of the nanofibers showed that even and continuous nylon 6 nanofibers were well prepared through electrospinning and that the organic photosensitizers were evenly distributed in the nanofibers. There was no significant reduction of crystallinity in the nylon 6 nanofibers through the insertion of the organic photosensitizers. After UV (365 nm) irradiation of the photosensitizers, the intensity of peak photon excitation in the electron spin resonance spectra was increased. Antimicrobial properties of the prepared nanofibers were tested against Staphylococcus aureus and Escherichia coli according to JIS Z 2801. It was found that antimicrobial properties of nylon 6 nanofibers containing MK and TX were superior to those of nylon 6 nanofibers containing conventionally used BP. The antimicrobial effects of the nanofibers for S. aureus were superior to those for E. coli. The antimicrobial activity gradually increased as the UV irradiation time increased. Copyright © 2012 Society of Chemical Industry     

Preparation and properties of silver‐containing nylon 6 nanofibers formed by electrospinning

Nylon 6 nanofibers containing silver nanoparticles (nylon 6/silver) were successfully prepared by electrospinning. The structure and properties of the electrospun fibers were studied with the aid of scanning electron microscopy, transmission electron microscopy, energy‐dispersive spectroscopy, and X‐ray diffraction. The structural analysis indicated that the fibers electrospun at maximum conditions were straight and that silver nanoparticles were distributed in the fibers. Finally, the antibacterial activities of the nylon 6/silver nanofiber mats were investigated in a broth dilution test against Staphylococcus aureus (Gram‐positive) and Klebsiella pneumoniae (Gram‐negative) bacteria. It was revealed that nylon 6/silver possessed excellent antibacterial properties and an inhibitory effect on the growth of S. aureus and K. pneumoniae. On the contrary, nylon 6 fibers without silver nanoparticles did not show any such antibacterial activity. Therefore, electrospun nylon 6/silver nanocomposites could be used in water filters, wound dressings, or antiadhesion membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Tensile properties of denture base resin reinforced with various esthetic fibers

This study was conducted to determine the reinforcement effect of five types of esthetic fibers on the tensile properties of a conventional denture base resin. E‐glass, polyester, rayon, nylon 6, and nylon 6/6 fibers were cut into 2, 4, and 6 mm lengths and added into resin randomly at a concentration of 3% by weight. For each formulation, five tensile specimens, as well as control specimens without fibers, were prepared in a dumbbell shape using a stainless steel mold, constructed according to ASTM Standard D638M‐91a. Tensile properties were evaluated by using a universal testing machine. Surfaces of the tensile sections were also observed under the scanning electron microscope (SEM). Tensile strength of the specimens reinforced with fibers in varying lengths was found to be lower than that of the unreinforced control group. Among the trial groups, the specimens reinforced with 6 mm long polyester fibers showed the highest tensile strength. All the SEM fractographs indicated both weak adhesion and pull out of fibers from the matrix. None of the incorporated esthetic fibers appeared to improve tensile strength of the resin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Sustainable biocomposites from biobased polyamide 6,10 and biocarbon from pyrolyzed miscanthus fibers

The reinforcing effects of biocarbon of varying particle size ranges (crushed, <500, 500–426, 250–213, and <63 µm) on biobased polyamide 6,10 (PA 6,10) at 20 wt % loading were investigated for the resulting biocomposites. The heat deflection temperature and impact strength were observed to increase with reduction in particle size. Also, a 200% increase in the impact strength was observed in the biocomposite with biocarbon particles sized at <63 µm when compared to that with <500 µm. A 50% and 83% increase in the tensile and flexural moduli of the biocomposite with biocarbon particle size of <500 µm was observed, respectively, while the tensile strength was observed to remain unchanged. The flexural strength of the biocomposites was improved by 61% when compared to neat nylon. These results were due to good wetting, dispersion and increased surface area of the biocarbon within the nylon matrix. These results show the potential of biocarbon as reinforcing filler in nylon for applications especially in the automotive industry. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44221.     

Ionic interphase of glass fiber/polyamide 6,6 composites

Interfacial polymerization to polyamide 6, 6 followed by introduction of ionic groups was performed on the surface of short glass fibers. The ionic interphase-modified fibers were used with poly(ethylene-co-methacrylic acid) (DuPont Surlyn) to prepare composites with specific fiber-matrix interactions. Fiber treatment increased composite tensile and bending properties. An increase in the average fiber length was observed, which was attributed to a decrease in the fiber attrition during mixing. The effect of increasing temperature on the composite mechanical properties was studied. Different behavior was observed before and after the glass transition temperature, T_g, of the matrix. The dynamic mechanical measurements showed an increase in the T_g of the matrix after the treatments, which is attributed to a decrease in chain mobility at the interface resulting from increased interactions of the treated fiber surface with the polymer. Scanning electron microscopy of fractured composites after tensile tests revealed a smooth fiber surface with no polymer at the surface for the untreated composites. Adhered polymer was clearly observed on the surface of treated fibers, indicating better fiber wetting by the matrix. This improved adhesion was attributed to the grafted nylon molecules at the glass fiber surface.     

Synthesis and characterization of short Grewia optiva fiber‐based polymer composites

Natural fibers, such as Flax, Sisal, Hibiscus Sabdariffa, and Grewia optiva (GO) possess good reinforcing capability when properly compounded with polymers. These fibers are relatively inexpensive, easily available from renewable resources, and possess favorable values of specific strength and specific modulus. The mechanical performance of natural fiber‐reinforced polymers (FRPs) is often limited owing to a weak fiber‐ matrix interface. In contrast, urea–formaldehyde (UF) resins are well known to have a strong adhesion to most cellulose‐containing materials. This article deals with the synthesis of short G. optiva fiber‐reinforced UF polymer matrix‐based composites. G. optiva fiber‐reinforced UF composites processed by compression molding have been studied by evaluating their mechanical, physical, and chemical properties. This work reveals that mechanical properties such as: tensile strength, compressive strength, flexural strength, and wear resistance of the UF matrix increase up to 30% fiber loading and then decreases for higher loading when fibers are incorporated into the polymer matrix. Morphological and thermal studies of the matrix, fiber, and short FRP composites have also been carried out. The swelling, moisture absorbance, chemical resistance, and water uptake behavior of these composites have also been carried out at different intervals. The results obtained lay emphasis on the utilization of these fibers, as potential reinforcing materials in bio‐based polymer composites. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Antimicrobial activity of bleached cattail fibers (Typha domingensis) impregnated with silver nanoparticles and benzalkonium chloride

Typha domingensis (Cattail) fiber is a significant natural resource, abundant in cellulose. The study reports the useful utilization of T. domingensis fiber for physicochemical impregnation of silver nanoparticles and benzalkonium chloride, in the development of a material with antimicrobial activity. The fibers were pre-treated with alkaline hydrogen peroxide (bleaching) for partial removal of lignin, pectin and waxes. Subsequently treated in a solution of different concentrations of benzalkonium chloride and Tollens' reagent. The new materials obtained were carefully investigated for their structure and thermal stability, morphology and susceptibility to antimicrobials (Staphylococcus aureus, Escherichia coli, Salmonella typhimuruim, and Salmonella enteritidis). Fourier transform infrared spectra showed the presence of benzalkonium chloride. The morphology analysis showed the silver nanoparticles on the surface of the bleached fibers. The susceptibility profile to antimicrobials was confirmed by the formation of inhibition halos (≅11.26 mm). Based on the properties of the materials obtained, it can be concluded that the modified cattail fibers have the potential to be used as a functional filler, or coating, in the development of antimicrobial composites.     

Bending and torsional fatigue of nylon 66 monofilaments

Using newly developed test equipment, the fatigue behavior of nylon 66 monofilaments was studied under two loading conditions, pure bending or simple torsion. For each mode, results are expressed in terms of the measured decay in stiffness with numbers of cycles over a range of maximum applied strain levels. Fatigue lifetimes are presented in S–N format where the log number of cycles of fatigue for a 40% decay in stiffness (N) is plotted as a function of applied strain (S). The failure mechanism for these fibers in each fatigue mode reflects the morphology of semicrystalline-oriented synthetic fibers. In torsion, many longitudinal cracks form around the perimeter of a fiber as the result of cleavage of the relatively weak interfibrillar bonds in nylon 66. In bending, cracks form within kink band boundaries and grow at an oblique angle to the fiber axis. © 1992 John Wiley & Sons, Inc.     

Polymeric phosphonium salts as a novel class of cationic biocides. VI. Antibacterial activity of fibers surface-treated with phosphonium salts containing trimethoxysilane groups

Alkoxysilane with phosphonium biocides as coupling agents were covalently attached to cotton-fiber surfaces, and the antibacterial activity of the surface-treated fibers against Staphylococcus aureus and Escherichia coli was evaluated by the viable cell counting method in sterile distilled water. These fibers with phosphonium salts were found to exhibit high antibacterial activity against S. aureus and E. coli, particularly against S. aureus, and the activity increased as hydrophobicity of the substituents bonded directly to phosphonium ions increased. Furthermore, morphological changes of the cells of S. aureus and E. Coli in contact with the fibers were evaluated by scanning electron microscopy. It was found that the fiber with the phosphonium biocides exhibited bacteriostatic as well as bactericidal activity against both strains, which was evident from observation of normal and deformed cells of these species in contact with the fibers. © 1994 John Wiley & Sons, Inc.     

Novel core‐sheath antimicrobial nanofibrous mats

The poor mechanical properties of electrospun materials remain one of the major hindrances toward their practical application. In this study, we report the synthesis of core‐sheath nanofibrous mats to enhance the mechanical properties of an antimicrobial polymer nanofiber for application in filter media. This objective was achieved via coaxial electrospinning of poly[styrene‐co‐N‐(N′,N′‐dimethyl‐3‐aminopropyl)maleimide] as the sheath which is an antimicrobial polymer and nylon 6 polymer for the core which is well reported for exceptional mechanical properties. Extensive characterization of these fibers was performed using scanning electron microscopy, scanning transmission electron microscopy, confocal fluorescence microscopy as well as attenuated total reflectance Fourier transform spectroscopy to provide evidence of the core‐sheath morphology. Antimicrobial evaluation was also carried out on the fabricated fibers via the live/dead fluorescence technique. This was done to determine if the poly[styrene‐co‐N‐(N′,N′‐dimethyl‐3‐aminopropyl)maleimide] retained its antimicrobial activity. The fibers were found to be effective against the Gram‐positive Staphylococcus aureus (ATCC25925) and Gram‐negative Pseudomonas aeruginosa (ATCC27853). Subsequent tensile testing and filtration experiments provided evidence that the incorporation of the nylon core improved mechanical properties of the nanofiber mats. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46303.     

Physicochemical and antimicrobial properties of natural rubber latex films in the presence of vegetable oil microemulsions

A series of vegetable oil microemulsions are formulated and incorporated into NR latex to study the potent antimicrobial activity of vegetable oil‐plasticized NR latex film against the adherent bacteria on the treated film. The particle size of latex incorporated with 2.50 phr of oil has attained up to 424 nm after incubated at 35 ± 2 °C for 24 h. The tensile stress of all NR latex films are relatively low, ranged 0.289 to 0.511 MPa. All emulsions are found compatible with NR and the low contact angles (<90°) corresponded to no oil blooming onto the surfaces of NR latex films. The crosslink densities are in good correlation with tensile strengths. The potent antimicrobial properties of the NR latex films are investigated from the viability assessment of the adherent tested Escherichia coli ATCC 25922 (E. coli ATCC 25922) and Staphylococcus aureus ATCC 25923 (S. aureus ATCC 25923). Results shows that NR latex film incorporated with palm kernel oil/soybean oil blend, NR‐E(P/S = 7/3), has significantly killed the adherent S. aureus with 92.5% reduction but showed no significant log reduction in E. coli. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44788.     

Comparison of antimicrobial activities of polyacrylonitrile fibers modified with quaternary phosphonium salts having different alkyl chain lengths

A series of polyacrylonitrile fibers (PANF) modified with quaternary phosphonium salts having various alkyl chain lengths (C₁, C₂, C₆, C₈, C₁₂) were synthesized and compared for their antimicrobial activities by the improved shake flask method. The as‐prepared fibers were named MTPB‐PANF, ETPB‐PANF, HTPB‐PANF, OTPB‐PANF, and DTPB‐PANF, respectively. The representative microorganisms employed were Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa), and Candida albicans (C. albicans). Results from the current study showed that the alkyl chain length of quaternary phosphonium salts not only affected the synthesis of the fibers, but also impacted their antimicrobial activities. There was a rule that the longer the alkyl chain length, the more easily the quaternary phosphonium salts modify the fibers and the better the antimicrobial activities of the modified fibers. All the modified fibers exhibited good broad‐spectrum antimicrobial activities. Specifically, DTPB‐PANF exhibited an outstandingly high antimicrobial activity, which was nearly unaffected by the environmental pH (3–10). It can kill all the four pathogens in 15 min and had an excellent wash‐resistant property. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43689.     

Berberine finishing for developing antimicrobial nylon 66 fibers: % exhaustion,colorimetric analysis,antimicrobial study,and empirical modeling

Berberine, a natural cationic colorant was successfully employed onto nylon 66 fiber in this research. The effects of three important variables, namely pH, temperature, and liquor ratio were examined on the % exhaustion, color strengths, and color yields of the sample. It has been employed in antimicrobial finishing as a natural agent on nylon 66 due to its characteristics of cationic quaternary ammonium salt. Antimicrobial activity of the sample was studied against Staphylococcus aureus (ATCC 6538) and Klebsiella pneumoniae (ATCC 4352) according to test method KS K 0693‐2001 and the corresponding berberine finished sample showed very effective antimicrobial functions showing about 99.9% of bacterial reduction against above‐mentioned two bacteria. The maximum % exhaustion, color strengths, and color yields were obtained at 98 °C, alkaline condition (pH 11) and lower liquor ratio (20 : 1). An appropriate predictable empirical models were also developed using Excel solver function incorporating interaction effects of all variables to predict the % exhaustion, color strength(K/S), and the satisfactory results (R² > 0.99) were obtained. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1175–1182, 2007     

Essential work of fracture (EWF) analysis for short glass fiber reinforced and rubber toughened nylon‐6

The effect of fiber content on the fracture toughness of short glass fiber reinforced and rubber toughened nylon‐6 has been investigated using the essential work of fracture (EWF) analysis under both quasi‐static and impact rates of loading. Under quasi‐static loading rate, matrix plastic deformation played a major role. Addition of 10 wt% of short glass fibers into a rubber toughened nylon‐6 matrix improved the fracture toughness substantially. This is due to the synergistic effect that comes from matrix yielding and fiber related energy absorption such as fiber debonding, fiber pull‐out and fiber fracture. With further increasing the glass fiber content, up to 20 and 30 wt%, even though plastic deformation could still take place on the fracture surfaces, the depth of the fracture process zones was much smaller when compared with the system with 10 wt% of glass fibers. The reduction in fracture process zone caused the reduction in fracture toughness. Under impact loading rate, the unreinforced blend still fractured in a ductile manner with gross yielding in the inner fracture process zone and the outer plastic zone. The unrein‐forced blend therefore possesseed higher fracture toughness. For the fiber reinforced blends, the matrix fractured in brittle manner and so fracture toughness of the reinforced blends decreased dramatically. The impact fracture toughness increased slightly after incorporation of a higher weight percentage of glass fibers.     

The influence of cooling rate on the fracture properties of a glass reiforced/nylon fiber-metal laminate

The effect of varying cooling rate on the microstructure and resulting mechanical properties of a novel fiber-metal laminate (FML) based on a glass fiber-reinforced nylon composite has been investigated. Polished thin sections removed from plain glass fiber/nylon composites and their corresponding fiber-metal laminates indicated that the prevailing microstructure was strongly dependent on the rate of cooling from the melt. Mode I and Mode II interlaminar fracture tests on the plain glass fiber reinforced nylon laminates indicated that the values of G_Ic and G_IIc averaged approximately 1100 J/m² and 3700 J/m² respectively at all cooling rates. The degree of adhesion between the aluminum alloy and composite substrates was investigated using the single cantilever beam geometry. Here, the measured values of G_c were similar in magnitude to the Mode I interlaminar fracture energy of the composite, tending to increase slightly with increasing cooling rate. The tensile and flexural fracture properties of the plain composites and the fiber metal laminates were found to increase by between 10% and 20% as the cooling rate was increased by two orders of magnitude. This effect was attributed to over-aging of the aluminum alloy plies at elevated temperature during cooling. Finally, fiber metal laminates based on glass fiber/nylon composites were shown to exhibit an excellent resistance to low velocity impact loading. Damage, in the form of delamination, fiber fracture, matrix cracking in the composite plies, and plastic deformation and fracture in the aluminum layer, was observed under localized impact loading. Here, the fast-cooled fiber metal laminates offered superior post-impact mechanical properties at low and intermediate impact energies, yet very similar results under high impact energies.     

Fracture and toughening behavior of aramid fiber/epoxy composites

The effect of short Aramid fibers on the fracture and toughening behavior of epoxy with high glass transition temperature has been studied. Fine dispersion of the fibers throughout the matrix is evidenced by optical microscopy. Compared with neat epoxy resin, the fracture toughness (K_IC) of the composites steadily increases with increasing fiber loading, indicating that addition of Aramid fibers has an effective toughening effect to the intrinsically brittle epoxy matrix. Scanning electron microscopy (SEM) indicates that formation of numerous step structures for fiber‐filled epoxy systems is responsible for the significant toughness improvement. SEM and transmitted optical microscopy show that fiber pullout and fiber breakage are the main toughening mechanisms for the Aramid fiber/epoxy composites. POLYM. COMPOS. 26:333–342, 2005. © 2005 Society of Plastics Engineers.     

Preparation of silver nanoparticle functionalized polyamide fibers with antimicrobial activity and electrical conductivity

In this work, silver nanoparticle functionalized polyamide 6 (PA6) fibers were prepared using the electroless plating method. The surface of PA6 fibers was modified by exploiting dopamine/CuSO₄/H₂O₂ system prior to electroless plating to enhance the bonding force between the fiber and the silver nanoparticles. It was found that both the formation rate and the chemical stability of polydopamine (PDA) coatings on the PA6 fiber surface were improved by the introduction of CuSO₄/H₂O₂. The results confirmed the successful deposition of silver nanoparticles on PA6 fiber surface and the average particle diameter of 223 nm. Compared with uncoated fibers, the silver plated PA6 fibers exhibited excellent antimicrobial activity to both Escherichia coli and Staphylococcus aureus (with an antimicrobial efficiency of 99.9% and 100%, respectively). The electrical resistance of the silver coated PA6 fibers reached 0.98 Ω over a length of 1 cm, indicating a good electrical conductivity. In particular, coating durability of the formed silver layer was investigated by subjecting the fibers to various mechanical deformations, and the results showed that the formed silver layer was maintained well after 50 times of cyclic stretching at a constant displacement of 10 mm. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47584.     

Antibacterial Properties of Tough and Strong Electrospun PMMA/PEO Fiber Mats Filled with Lanasol—A Naturally Occurring Brominated Substance

A new type of antimicrobial, biocompatible and toughness enhanced ultra-thin fiber mats for biomedical applications is presented. The tough and porous fiber mats were obtained by electrospinning solution-blended poly (methyl methacrylate) (PMMA) and polyethylene oxide (PEO), filled with up to 25 wt % of Lanasol—a naturally occurring brominated cyclic compound that can be extracted from red sea algae. Antibacterial effectiveness was tested following the industrial Standard JIS L 1902 and under agitated medium (ASTM E2149). Even at the lowest concentrations of Lanasol, 4 wt %, a significant bactericidal effect was seen with a 4-log (99.99%) reduction in bacterial viability against S. aureus, which is one of the leading causes of hospital-acquired (nosocomial) infections in the world. The mechanical fiber toughness was insignificantly altered up to the maximum Lanasol concentration tested, and was for all fiber mats orders of magnitudes higher than electrospun fibers based on solely PMMA. This antimicrobial fiber system, relying on a dissolved antimicrobial agent (demonstrated by X-ray diffraction and Infrared (IR)-spectroscopy) rather than a dispersed and “mixed-in” solid antibacterial particle phase, presents a new concept which opens the door to tougher, stronger and more ductile antimicrobial fibers.