Synthesis of polypyrrole nanocomposites decorated with silver nanoparticles with electrocatalysis and antibacterial property

Polypyrrole nanowire/silver nanoparticle composites (PPy/Ag) are obtained in aqueous media through a one-pot method without any external stimulus. PPy nanowires were assembled on the reactive self-degraded template of the complex of AgNO₃ and methyl orange (MO). During the synthesis process in the dark surrounding, Ag nanoparticles could be uniformly decorated onto the surface of PPy nanowires in situ by the redox reaction of pyrrole and AgNO₃. Neither additional reducing agents for the growth of silver nanoparticles nor oxidizing agents for the polymerization of pyrrole are utilized. The formation mechanism, morphologies, structural characteristics, and conductivity of the obtained PPy/Ag nanocomposites are reported. The as-prepared PPy/Ag nanocomposites exhibit well-defined response to the electrochemical reduction of hydrogen peroxide. Moreover, the preliminary antibacterial assays indicate that the PPy/Ag nanocomposites also possess antibacterial abilities against Escherichia coli.     

Removal of oil from water using magnetic bicomponent composite nanofibers fabricated by electrospinning

In the present study, a magnetic nanofibrous composite mat composed of polystyrene (PS)/polyvinylidene fluoride (PVDF) nanofibers with selective incorporation of iron oxide (Fe₃O₄) nanoparticles (NPs) on/in PS was successfully prepared via a facile two-nozzle electrospinning process for oil-in-water separation. Field emission scanning electron microscopy and infrared spectroscopy showed the mats to be highly-porous in structure and confirmed the presence of the Fe₃O₄ NPs on/in the nanofibers. Both PS and PVDF nanofibers exhibited oleophilic and hydrophobic properties. The results showed improved mechanical properties when PVDF was added to the composite mat compared to the pristine PS mat. In addition, the incorporation of magnetic Fe₃O₄ NPs in the composite mat helps in the easy recovery of the mats after the oil-in-water sorption process. The composite mats showed good oil sorption capacity (35–46 g/g) and improved mechanical property. The present electrospun magnetic PVDF/Fe₃O₄@PS nanofibers could be potentially useful for the efficient removal of oil in water and recovery of sorbent material.     

Effect of the temperature on surface modification of silica and properties of modified silica filled rubber composites

The modified silica at different temperature (MSaDT) with bis(3-triethoxysilylpropyl)tetrasulfide (TESPT), and MSaDT filled solution styrene butadiene rubber (SSBR) composites were prepared to investigate the effect of temperature on surface modification of silica. The results showed that TESPT was successfully bonded on the surface of silica by chemical bonds. The grafting degree (K) of MSaDT of 50 °C was 62.2% and higher than that at the other temperatures. The thermal weight loss and the size distribution of MSaDT showed that the silanol of TESPT hydrolysates reacted with the surface hydroxyl groups of silica, decreasing the average size and agglomeration of modified silica. For 50 °C modified silica/SSBR composite, the static mechanical properties and rubber–filler interaction of the composite were better than those of the others. As far as dynamic mechanical properties are concerned, the 50 °C modified silica/SSBR composite owned a best combination of low rolling resistance and high wet skid resistance.     

Influence of hygrothermal aging on carbon nanofiber enhanced polyester material systems

Four polyester composites (neat polyester, polyester reinforced with glass fibers, polyester reinforced with carbon nanofibers, and polyester reinforced with both glass fibers and carbon nanofibers) were prepared with the Vacuum Assisted Resin Transfer Molding (VARTM) process. These material systems were exposed to 60 °C/60% RH for 3600 h. Diffusivity was determined using moisture uptake curves. And, it was discovered that the addition of glass fibers (GFs) increased diffusivity, while the addition of carbon nanofibers (CNF) decreased diffusivity. Optical analysis was performed on the manually delaminated glass fiber reinforced polymer (GFRP) and nano-enhanced GFRP. This analysis indicated that the addition of CNF retarded the degradation of the matrix after exposure to elevated heat and humidity. Thermo-mechanical analysis was performed across material systems during various stages of the environmental preconditioning to determine alterations in properties such as storage modulus (SM) and glass transition temperature (T_g). The addition of GF to the system initially increased the maximum storage modulus, it also increased degradation from elevated heat and humidity exposure In contrast with GF, the addition of CNF retarded SM degradation and increased thermal stability. Upon re-drying, the nano-enhanced material systems recouped more than 90% of the maximum SM and maintained a T_g between the baseline and saturated hygrothermal treatments. This indicated both a reversible plasticization and an irreversible retarded degradation which could be potentially attributed to the addition of CNF.     

Preparation of modified nano ZnO/polyester/TGIC powder coating nanocomposite and evaluation of its antibacterial activity

Powder coating nanocomposite with antibacterial properties is the aim of this study. For this purpose, nano zinc oxide was modified by vinyltrimethoxysilane (VTMS) and Triethoxy(methyl)silane (TEMS). Then various percentages of modified and non-modified nano ZnO (1, 3 and 5%), polyester resin and triglycidyl isocyanurate as a hardener were blended by twin screw extruder. Prepared polymer–matrix composite (PMC) was atomized and coated by electrostatic method on aluminum plates. Finally, samples were cured for 10 min at 200 °C. For investigating the thermal stabilities of modified nano particles, thermogravimetric analyses (TGA) were used. Antibacterial properties of coatings were investigated by gram negative bacteria Escherichia coli and gram positive Staphylococcus aureus. The results showed that the coatings demonstrate significant antibacterial activity by increasing amounts of ZnO nanoparticles (5%) when were modified by VTMS.     

Preparation and tribological performance of chemically-modified reduced graphene oxide/polyacrylonitrile composites

Interface control and dispersion of graphene base nanomaterials in polymer matrix are challenging to develop high comprehensive nanocomposites due to their strong interlayer cohesive energy and chemical inertia. In this research, an efficient approach is presented to functionalize reduced graphene oxide nanosheets by N-[3-(trimethoxylsilyl)propyl]ethylenediamine, which is dispersed into polyacrylonitrile to prepare N-[3-(trimethoxylsilyl)propyl]ethylenediamine – reduced graphene oxide/polyacrylonitrile nanocomposites. A thermogravimetric analysis technique was employed to evaluate thermal properties of the nanocomposites. The tribological properties of the polyacrylonitrile/graphene nanocomposites were investigated. The morphologies and volume of the worn surface were examined using a 3D profilometer. The impact of loading ratio on friction coefficient, carry-bearing capacity and durability were studied. The N-[3-(trimethoxylsilyl)propyl]ethylenediamine – reduced graphene oxide/polyacrylonitrile nanocomposite with appropriate loading ratio of reduced graphene oxide exhibited a high load-bearing capacity and durability. Therefore, the polyacrylonitrile/graphene nanocomposite shows promising potential to industrial applications involving the lubrication and anti-wear.     

Preparation of ultra-low dielectric constant silica/polyimide nanofiber membranes by electrospinning

Ultra-low dielectric constant silica/polyimide (SiO₂/PI) composite nanofiber membranes are prepared by the combined sol–gel and electrospinning techniques. The emulsion composed of partially hydrolyzed tetraethoxysilane (TEOS) and polyamic acid (PAA) is spun to yield the precursor of the SiO₂/PI fibers with a core–shell structure due to phase separation. The dielectric constant (k) of the composite membranes varies from 1.78 to 1.32 with increasing content of SiO₂. The fibers accumulate and form the film with a large amount of pores leading the lower k. In addition, the interfacial reaction between SiO₂ and the PI matrix reduces the value of k as the SiO₂ concentration is increased. The thermal stability of PI increase after mixing with SiO₂ and the SiO₂/PI composite fibers have large commercial potential in the electronics industry.     

Hybrid carbon nanotube–carbon fiber composites with improved in-plane mechanical properties

In this study carbon nanotubes (CNTs) were grown on carbon fibers to enhance the in-plane and out-of-plane properties of fiber reinforced polymer composites (FRPs). A relatively low temperature synthesis technique was utilized to directly grow CNTs over the carbon fibers. Several composites based on carbon fibers with different surface treatments (e.g. growing CNTs with different lengths and distribution patterns and coating the fibers with a thermal barrier coating (TBC) layer) were fabricated and characterized via on- and off-axis tensile tests. The on-axis tensile strength and ductility of the hybrid FRPs were improved by 11% and 35%, respectively, due to the presence of the TBC and the surface grown CNTs. This configuration also exhibited 16% improvement on the off-axis stiffness. Results suggest that certain CNT growth patterns and lengths are more pertinent than the other surface treatments to achieve superior mechanical properties.     

Molecular characterizations,mechanical properties and anti-algal activities for PVC and wood/PVC composites containing urea- and triazine-based algaecides

Material behaviors and anti-algal performances of PVC and wood PVC composites (WPVCs) were examined after adding commercial algaecides of different types and contents. Three different wood types commonly found in tropical climates – namely, Xylia kerrii Craib and Hutch.; Hevea brasiliensis Muell.; and Mangifera indica Linn. – were of interest. Isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea), a urea-based algaecide, and Terbutryn (N²-tert-butyl-N⁴-ethyl-6-methylthio-1,3,5-triazine-2,4-diamine), a triazine-based algaecide, were used as anti-algal agents in this study; concentrations in the specimens varied from 0 to 1500 ppm. Surface color, thermal properties, chemical structure and mechanical properties of the materials were also monitored. The results revealed that addition of Isoproturon tended to considerably change the surface color of the materials, particularly for PVC which had the highest ΔE^* value, whereas addition of Terbutryn did not. The effect of wood types was found to influence the initial surface color of the materials. Evidence based on DSC, FT-IR and contact angle testing indicated that Isoproturon had a strong molecular interaction with PVC and could induce PVC degradation. The mechanical properties of PVC and WPVC were affected by the addition of wood, but not by algaecide addition. The results of the growth inhibition zone and chlorophyll-a content in Chlorella vulgaris TISTR 8580 suggested that Terbutryn exhibited better anti-algal performance than Isoproturon with a recommended dosage of 1000 ppm while Isoproturon at 1500 ppm could act as an effective coupling agent in WPVC composites.     

Effect of graphene oxide nanosheets on the physico-mechanical properties of chitosan/bacterial cellulose nanofibrous composites

In this work, novel chitosan/bacterial cellulose (CS/BC) nanofibrous composites reinforced with graphene oxide (GO) nanosheets are introduced. As cell attachment and permeability of nanofibrous membranes highly depend on their fiber diameter, the working window for successful electrospinning to attain sound nanofibrous composites with a minimum fiber diameter was determined by using the response surface methodology. It is shown that the addition of GO nanosheets to CS/BC significantly reduces the average size of the polymeric fibers. Their mechanical properties are also influenced and can be tailored by the concentration of GO. Fourier transform infrared spectroscopy reveals hydrogen bonding between the GO nanosheets and the polymer matrix. A decrease in the hydrophilicity of the electrospun nanofibers and their water vapor permeability with the addition of GO are also reported. The prepared nanofibrous composites are potentially suitable candidates for biomedical applications such as skin tissue engineering and wound dressing.     

Synthesis and properties of amphiphilic block polymer functionalized multi-walled carbon nanotubes and nanocomposites

The grafting of poly(ethylene glycol)-block-polyacrylonitrile (PEG-b-PAN) amphiphilic block polymer onto multi-walled carbon nanotubes (MWCNTs) was achieved by combination of coupling reaction and redox radical polymerization. The chemical structure and yield of the resulting grafted polymer were characterized and confirmed by FT-IR and TGA. Transmission electron microscopy (TEM) images clearly indicated that the nanotubes were coated with a polymer layer. The concentrated DMF dispersions of MWCNT-g-(PEG-b-PAN) nanocomposite were stable for months, the viscoelasticity being monitored by rheometer. MWCNT-g-(PEG-b-PAN) hybrid nanocomposite membranes were fabricated by phase inversion in a wet process. The results showed that high concentration of MWCNTs could be dispersed in the polymer matrix. The morphology and surface hydrophilicity characteristics of the membrane could be controlled by the composition of MWCNT-g-(PEG-b-PAN) nanocomposite membrane.     

Supramolecular aromatic interactions to enhance biodegradable film properties through incorporation of functionalized cellulose nanocrystals

Cellulose nanocrystals (CNC) were grafted with an aliphatic and an aromatic isocyanate (octadecyl and 4-phenylbutyl isocyanate) and composites of poly(butyleneadipate-co-terephthalate) – PBAT – with 5 and 10 wt% of modified and non-modified CNC were prepared through solvent casting. Rheological analysis confirmed that the degree of grafting contributed to CNC dispersion and allowed the formation of a percolated structure. The treated-CNC reinforced composites displayed improved mechanical properties, namely: an increase by 120% and 40% in the elastic modulus and the tensile strength, respectively. The best results were obtained with 4-phenylbutyl isocyanate-modified CNC, due to the π–π interactions between the phenyl rings grafted onto the CNC molecules and the aromatic rings of the polymeric chain, as indicated by Raman spectroscopy. To the best of our knowledge, it is the first time that the CNC incorporation is studied in a PBAT pure matrix.     

Biodegradable electrospun nanocomposite fibers based on Poly(2-hydroxy ethyl methacrylate) and bamboo cellulose

Electrospun fibers resemble extracellular matrix and are successfully being used in drug delivery and wound healing. The present study reports the extraction of cellulose from natural fiber such as bamboo which is cost effective. It was then added to Poly(2-hydroxy ethyl methacrylate) (pHEMA) solution and electrospun to obtain pHEMA-bamboo cellulose nanocomposite fibers. The characterization of the prepared bamboo cellulose, pHEMA-bamboo cellulose nanocomposite fibers were carried out using FTIR, XRD, TGA and SEM analysis. The biocompatibility of the prepared nanocomposite fiber were studied by MTT extraction method using Vero cell lines. Similarly the anticancer activity of paclitaxel incorporated nanocomposite fibers were assessed using MCF 7 cancer cell lines. The prepared nanocomposite fibers showed 96% cell viability and the paclitaxel incorporated pHEMA-bamboo cellulose nanocomposite fiber showed 7.4% cancer cell viability in 72 h. This proves the applicability of the prepared polymer matrix composite fiber as a fibrous mesh covering the affected skin area for skin cancers or wound healing.     

Optical and mechanical anisotropies of aligned electrospun nanofibers reinforced transparent PMMA nanocomposites

This study aims to assess the nanofiber directionality effects on optomechanical properties of a widely used transparent thermoplastic poly(methyl methacrylate) (PMMA). Aligned fiber-hybrid mats consisted of nylon-6 (PA-6) nanofibers and PMMA microfibers are prepared using a self-blending co-electrospinning method, followed by hot press molding to fabricate into transparent nanocomposites. Effects of nanofiber orientation degree in two orthogonal directions and loading fraction on the optomechanical behavior of the nanocomposites are examined. Optical transmittance differences parallel and perpendicular to the nanofibers’ orientation are found to vary in a range of 3.9–5.4% at 589 nm, and strong mechanical anisotropy is observed with the 1% PA-6/PMMA nanocomposites. A maximal of 3% PA-6 nanofiber loading maintains the nanocomposite high transmittance (>75%) with improved strength and toughness along the nanofiber axis. This study reveals evident anisotropic optomechanical properties of transparent nanocomposites, and highlights the great designability of transparent nanocomposites by using aligned nanofibers as the designing elements.     

Uniaxially aligned electrospun fibers for advanced nanocomposites based on a model PVOH-epoxy system

This work demonstrates the potential of aligned electrospun fibers as the sole reinforcement in nanocomposite materials. Poly(vinyl alcohol) and epoxy resin were selected as a model system and the effect of electrospun fiber loading on polymer properties was examined in conjunction with two manufacturing methods. A proprietary electrospinning technology for production of uniaxially aligned electrospun fiber arrays was used. A conventional wet lay-up fabrication method is compared against a novel, hybrid electrospinning–electrospraying approach. The structure and thermomechanical properties of resulting composite materials were examined using scanning electron microscopy, dynamic mechanical analysis, thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, and tensile testing. The results demonstrate that using aligned electrospun fibers significantly enhances material properties compared to unreinforced resin, especially when manufactured using the hybrid electrospinning–electrospraying method. For example, tensile strength of such a material containing only 0.13 vol% of fiber was increased by ∼700%, and Young’s modulus by ∼250%, with concomitant increase in ductility.     

Electrical and dielectric properties of polypropylene nanocomposites based on carbon nanotubes and barium titanate nanoparticles

Functional polypropylene (PP) nanocomposites were prepared by melt compounding with multiwalled carbon nanotubes (MWNT) as the electrically conductive component and barium titanate (BT) spherical nanoparticles as the ferroelectric component. To make PP electrically conductive, more than 3 wt.% MWNT is required. Surface modification of either MWNT or BT with titanate coupling agent further improves the electrical conductivity of the PP/MWNT/BT ternary nanocomposites. Interestingly, by modifying both MWNT and BT, 2 wt.% MWNT are sufficient to make the ternary nanocomposite electrically conductive. In addition, the incorporation of MWNT greatly increases the dielectric permittivity of PP/BT nanocomposites. However, to retain a low dielectric loss, the MWNT loading should be slightly less than the percolation threshold of the nanocomposites. The improved electrical conductivity and dielectric properties make the ternary nanocomposites attractive in practical applications.     

Effect of TiO2 on photocatalytic activity of polyvinylpyrrolidone fabricated via electrospinning

Polyvinylpyrrolidone (PVP) is a promising material for electrospinning, and it has many desirable properties, including solubility in various solvents, physiological compatibility, chemical inertness, and excellent film-forming ability. Polymer–matrix composites of PVP–carbon fibers containing TiO₂ were prepared via electrospinning. Degradation of environmental pollutants by the electrospun webs was evaluated based on methylene blue degradation. The optimum photocatalytic activity was achieved with webs containing 7 wt% TiO₂. The results show that the proposed method is effective for improving the photocatalytic properties of TiO₂-doped nanofibers; the doping process also increased the nanofiber surface area.     

Improving the mechanical properties of multiwalled carbon nanotube/epoxy nanocomposites using polymerization in a stirring plasma system

Uniform treatment of multiwalled carbon nanotubes by plasma treatment has been investigated using a custom-built stirring plasma system. A thin plasma polymer with high levels of amine groups has been deposited on MWCNTs using a combination of continuous wave and pulsed plasma polymerization of heptylamine in the stirring plasma system. Scanning electron microscopy showed that the plasma polymerization improved the dispersion and interfacial bonding of the MWCNTs with an epoxy resin at loadings of 0.1, 0.3 and 0.5 wt%. The flexural and thermal mechanical properties of plasma polymerized MWCNT/epoxy nanocomposites were also significantly improved while untreated MWCNT/epoxy nanocomposites showed an opposite trend. The epoxy with 0.5 wt% plasma polymerized MWCNTs had the greatest increase in flexural properties, with the flexural modulus, flexural strength and toughness increasing by about 22%, 17% and 70%, respectively.     

Hybrids of silver nanowires and silica nanoparticles as morphology controlled conductive filler applied in flexible conductive nanocomposites

Flexible conductive polymer nanocomposites based on silver nanowires (AgNWs) have been widely studied to develop the next generation of flexible electronics. However, AgNWs tend to aggregate in polymer matrix that usually results in high percolation threshold. In this study, nonconductive silica nanoparticles (nano-SiO₂) were successfully co-assembled on AgNWs to form AgNWs/nano-SiO₂ hybrids and waterborne polyurethane (WPU) conductive nanocomposites filled with the hybrids were prepared. The results show that the resistivity of WPU nanocomposites filled with AgNWs/nano-SiO₂ hybrids decreased about 5000 times and the percolation threshold decreased from 10.6 vol% to 3.6 vol% due to AgNWs distribute more uniformly in WPU with the help of nano-SiO₂. The further study to mechanism of interactions between AgNWs and nano-SiO₂ suggest that the promotion of dispersion is attributed to hydrogen bonding and van der Waals force. The WPU nanocomposites embedded with AgNWs/nano-SiO₂ hybrids present excellent mechanical adhesiveness, flexibility and thermal stability.     

Improved electrical insulating properties of LDPE based nanocomposite: Effect of surface modification of magnesia nanoparticles

Three silane coupling agents with amino, long alkyl chain or vinyl functional groups were used to modify magnesia (MgO) nanoparticles. The modified nanoparticles were then mechanically mixed with low-density polyethylene (LDPE) to fabricate insulating nanocomposites. The average size of the modified MgO aggregates dispersed in LDPE matrix was below 100 nm. The pulsed electroacoustic method indicated that the MgO nanoparticles regardless of surface modification were effective to suppress the packet-like charge injection and accumulation in the LDPE sample, decrease the permittivity and tan δ, and also improved the direct-current breakdown strength of LDPE at different temperatures. The best insulating properties were found in the case of vinyl-silane-modified-MgO/LDPE samples probably owing to the improved interfacial adhesion. A multi-core model was used to discuss the results obtained.