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Green synthesis may be a useful approach to achieve selective cytotoxicity of silver nanoparticles on cancer cells and healthy cells. In this study, the concomitant biosynthesis of silver (Ag)/silver chloride (AgCl) nanoparticles from pineapple peel extracts and their behavior on the breast cancer cell line MCF-7 is shown. Bioreactions were monitored at different temperatures. Fourier-transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), thermogravimetric analysis (TGA), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques were used to characterize nanoparticle development. The breast cancer cell line MCF-7 was used as a test model to study the cytotoxic behavior of Ag/AgCl nanoparticles and, as a counterpart, the nanoparticles were also tested on mononuclear cells. Ag/AgCl nanoparticles with spherical and triangular morphology were obtained. The size of the nanoparticles (10–70 nm) and the size distribution depended on the reaction temperature. A dose close to 20 µg/mL of Ag/AgCl nanoparticles considerably decreased the cell viability of the MCF-7 line. The best cytotoxicity effects on cancer cells were obtained with nanoparticles at 60 and 80 °C where cell viability was reduced up to 80% at a concentration of 50 µg/mL. A significant preference was observed in the cytotoxic effect of Ag/AgCl nanoparticles against cancer cells in comparison to monocytes.

Graphic abstract Graphene decorated with cooper nanostructures were prepared with and without ionic liquid (IL) using different milling times. The obtained samples were characterized by Raman, X-ray diffraction (XRD) and transmission electron microscopy (TEM), to analyze the effect of the grinding time on the copper particles adhesion to the graphene sheets. Composites of silicon with two contents of G/Cu, at two weight ratios, nanostructures were prepared and the crosslinking characteristics were analyzed by a rubber process analyzer. The thermal conductivity, electrical resistivity and antimicrobial characteristics against E. coli and S. aureus for these silicon/G/Cu composites were determined. It was found that the use of IL enhances the G/Cu nanostructures dispersion into the silicon polymer matrix with a noticeable improvement in thermal conductivity of 1.12 W/mK for a 7 wt% of G/Cu, a volume electrical resistivity of 4.1 × 1010 Ω cm with 7 wt% of G/Cu nanoparticles and antimicrobial response of 4.21 ± 0.11 to E. coli and 5.33 ± 0.11 to S. aureus with 7% of G/Cu nanoparticles. It was determined that π–π interactions between graphene and aromatic molecule of IL may be influencing the observed improvement in G/Cu dispersion and final composite performance. The novelty of this work is the use of IL to improve the G/Cu NPs dispersion into the silicon polymer matrix. This silicon/G/Cu composite could be an option to prepare medical devices for electrotherapy or face protection against COVID-19 or other silicon-based devices for medical applications.

Polypropylene composites and multi-walled carbon nanotubes (MWCNTs) modified with maleic anhydride (MA) and itaconic anhydride (IA) were prepared and their effect on the performance of nanocomposit...

The capillary infiltration of the Zn-22Al-2Cu (Zinalco) alloy into NaCl packed particles of sizes 496, 687, and 945 μm was studied using centrifugal casting. The threshold pressure for infiltration of NaCl particles with Zinalco was deduced experimentally, which increased as the diameter of the particles decreased. The work of immersion was determined from the threshold pressure with a value of 2.1. The infiltration proceeded at distinctly different rates for the three particle sizes studied. An equation to predict the threshold pressure to infiltrate Zinalco alloy into NaCl particles for given particle size and volume fraction was established. The micromechanical analysis showed that the strength of the foam depended strongly on the level of infiltration of the derived foam. As the level of infiltration increased, the stress distribution in the foams produced became homogeneously distributed in all the struts that make up the cell, which increases the strength of foam. The elastic modulus of the as-produced Zinalco foams is governed by structural parameters such as the pore size and the strut length. Thinner and shorter struts in the foam increase its ability to resist elastic deformation in the foam.

This work shows the preparation of ethylene vinyl acetate copolymer/banana starch/Cloisite 20A organoclay (EVA/starch/C20A) nanocomposites by melt processing. Wide angle X-ray diffraction (WAXD), field emission scanning electron microscopy (FE-SEM), differential scanning calorimetry and thermogravimetric analysis were used to characterize the obtained nanocomposites. Mechanical properties were also determined. In addition, the performance of the nanocomposite films under composting was preliminarily studied; it was conducted using the soil burial test method. Despite knowing that the starch is difficult to process by extrusion, nanocomposite films with high homogeneity were obtained. In this case, C20A organoclay acts as an effective surfactant to make the starch natural polymer compatible with the EVA synthetic polymer. The good compatibility between EVA, starch and C20A clay was also deduced by the formation of intercalated and intercalated-exfoliated structures determined by WAXD and FE-SEM. Physical evidence of the damage in EVA/starch/C20A nanocomposite films after the composting test was observed. It is worth noting that despite the absence of starch, the EVA/C20A nanocomposite film, used as a control, also showed surface damage. This behavior is related to the organic modifier linked to clay C20A, which contains molecules derived from fatty acids that can be used as a food source for microorganisms.

The synthesis of silver nanoparticles (AgNPs) using a Stevia rebaudiana aqueous extract and their dispersion in starch in order to obtain starch/AgNps nanocomposites are shown in this study. The AgNPs and the starch/AgNPs nanocomposites have been characterized by ultraviolet–visible spectroscopy, optical microscopy, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and thermogravimetric analysis. Furthermore, the interaction of starch/AgNPs nanocomposites with a MCF-7 breast cancer cell line is analyzed. AgNPs with an average size around 15–20 nm have been obtained. starch/AgNPs nanocomposite morphology changes with the content of silver (3, 5 and 8 mM), from totally separated and dispersed nanoparticles to ribbon-type morphology. The diffraction pattern of the starch/AgNPs-3 nanocomposite indicates the formation of silver chloride nanoparticles (AgClNPs). A cytotoxic behavior of starch/AgNPs-3 nanocomposite on MCF-7 cancer cells with less damage to normal cells is observed. Hence, the high dispersion of the AgNPs or AgClNPs in starch could be influencing the selective cytotoxic behavior. Thus, this study proposes the generation of biocompatible composite materials, with AgNPs immobilized on starch. These materials have selective action against breast cancer cells, where the selectivity is controlled through the AgNPs dispersion on the biopolymer.

The effect of ultrasonic (US) irradiation on solutions of low-density polyethylene (LDPE) was studied. Different irradiation times and intensities were examined. It was found that gel content increased very little as a result of US irradiation. However, this increase showed no variation with either the US irradiation time or intensity. The IR spectra of irradiated LDPE showed new absorption bands, indicating the presence of C–O groups, assumed to be the result of the US irradiation. GPC showed that the LDPE average molecular weight (Mw) decreases with an increase in either the US irradiation time or intensity. But these MWD curves, however, do not say if the “observed” modifications in Mw are due to chain scission or chain branching, which was inferred from the chain scission distribution function (CSDF) curves. From the GPC curves, it appears that chain scission is the dominant reaction at all US irradiation times and intensities. On the contrary, using the CSDF methodology, it appears that chain scission is the dominant reaction up to the intermediate irradiation times and intensities, but chain branching becomes dominant at the US higher times and intensities. On the contrary, using the proposed methodology, it appears that chain scission is the dominant reaction up to the intermediate irradiation times and power intensities, but chain branching becomes dominant at higher times and power intensities.

For the first time the combination of keratin fibers (KF), obtained from poultry feathers, with deoxyribose nucleic acid (DNA) are employed in low-density polyethylene-ethylene vinyl acetate (LDPE/EVA) blends in order to reduce the conventional hydroxide content and enhance the blend flame retardant properties. The combined effect of each filler and the use of maleated polyethylene (PEgMA) as compatibilizer on PE/EVA flame retardant properties was analyzed. DNA by its chemical structure can be considered as an intumescing agent and when it is combined with keratin the char formation is promoted and the flame retardant properties are enhanced. DNA was distributed in specific layers forming a segregated film which resulted in better PE/EVA blend flame retardant properties compared with either DNA deposited simply by compression molding on the material surface or with melt compounding in the bulk. The flame retardant behavior was compared with a reference PE/EVA sample with 55 wt% of Magnesium Hydroxide currently used for wire coatings in the wire and cable industry. The additives combination with DNA deposited as a segregated structure significantly increases the LOI up to 24.5% and reduces the heat release rate by 82% during cone calorimetry tests with very similar flame behavior as the reference sample with 55 wt% magnesium hydroxide loadings. The mechanical properties indicated that DNA has a marked increase in elongation as well as a marked reduction in torque and viscosity indicating that the combination of these additives can improve the mechanical performance, as well as facilitate the melt processing. Most important, the results indicated that the combination of these additives makes it possible to reduce the total Magnesium hydroxide filler content from 55 to 20 wt% to achieve the flame retardant requirements and with enhanced mechanical performance. Thus, this additives combination and this coating methodology provides a promising way to meet the growing demand and stringent requirements for high performance materials with high flame retardant standards using high efficient and green fire retardant coatings.

The curing reaction of the epoxy system “diglycidyl ether of bisphenol-A” (DGEBA) and the tertiary amine “2-[(2-dimethyl-amino)-ethoxy] ethanol” (DMAE), with different DMAE concentrations was studied by means of rheometric analysis using the Rubber Process Analyzer (RPA). A novel simple technique was introduced in order to allow the use of the RPA instrument in measuring the curing studies of quasi liquid reactants. It was found that the crosslinking degree; as measured by: a)- the maximum torque in the RPA analysis as well as by b)- the estimated molecular weight between crosslinks (Mc); increased with the DMAE concentration. Also, it was found that the curing reaction rate, increased with the DMAE concentration; greatly decreasing the time to gel point as well as the time to maximum torque. The degree of crosslinking, as taken from the crosslink density or by the molecular weight between crosslinks, increases roughly seven times as the tertiary amine (DMAE) concentration increases from 3 to 10 wt%. The activation energy of the crosslinking reaction was determined by plotting as an Arrhenius type equation, the log(Geltime) -vs- the inverse temperature, and it was found to be around 42.9 kJ/mol.

In this study, the combination of organomodified montmorillonite (MMT), magnesium hydroxide (MDH), graphene oxide (GO) and expandable graphite (EG) as intumescent flame retardant for Linear...

The effect of three different organomodified nanoclays (Cloisite 20A, Cloisite 30B, and Nanomer I28E) as well as the effect of a compatibilizer (PEgMA) was studied, with the purpose of developing g...

Maleic anhydride-grafted polypropylene (PP-g-MA) was reacted with aniline (NH2C6H5) to produce PP-g-NHC6H5 and used as a compatibilizer in polypropylene/carbon nanotube composites. Infrared spectroscopy (FTIR) and nuclear magnetic resonance confirmed the reaction between PP-g-MA and aniline. PP-g-NHC6H5 resulted a better compatibilizer than PP-g-MA, producing good dispersion and homogeneous distribution of the carbon nanotubes with less agglomerates, as observed by SEM analysis. Improved dispersion and distribution is assumed to be due to the π–π interactions between the –C6H5 ring in the prepared compatibilizer and the hexagonal carbon structure in the nanotubes. In addition, a higher degree of crystallinity (12%) was promoted, since it was favored by π–π interactions. This achieved higher crystallinity promoted an increase in tensile modulus, with only slight changes in tensile strength but with an adverse effect on elongation at break.

Graphene oxide (GO) derived from oxidation of natural graphite contains many active groups that can interact with a great variety of polar moieties. In this work, polypropylene (PP)/graphene oxide nanocomposites using polypropylene (PP) grafted with amine-alcohol (PPgDMAE) as compatibilizer were prepared by two different methods. Maleic anhydride grafted PP (PPgMA) was reacted with 2-[2-(dimethylamine)-ethoxy] ethanol (DMAE) in the melt for forming amine-alcohol functionalized polypropylene (PPgDMAE). Nanocomposites were prepared by two methods. In one method, PP/GO nanocomposite was prepared by direct melt mixing in an internal batch mixer using PPgDMAE as compatibilizer. In another method, a previous mixing of PPgDMAE with GO in hot Xilene was done and then, once the solvent was evaporated, it was incorporated into PP by melt-mixing. The microstructure and interface enhancement of the prepared composites were analyzed by Fourier transform infrared spectroscopy (FTIR), Raman, X-ray difraction (DRX) contact angle, scanning and transmission electron microscopy (STEM), mechanical, thermal, and electrical properties measurements. Fourier transform infrared spectroscopy (FTIR) revealed the interaction between GO and PPgDMAE. The loading of GO conducted to enhance the composite mechanical properties attributed to the strong interfacial interactions between GO and PPgDMAE. A significant improvement in mechanical thermal stability and electrical properties was observed when nanocomposites were prepared by the solution blending method compared with melt mixing method. This work suggests a potential application of GO in preparation of high performance PP composites. POLYM. COMPOS., 2016. © 2016 Society of Plastics Engineers

In this work the preparation and characterization of a multilayer film reservoir with clay/essential oil (EO) composites is described. The goal is to analyze the potential use of these reservoirs with clay/EOs composites as aroma-controlled release for various applications such as pesticide or attractant for pest control as well as antimicrobial. Two types of clays were analyzed, porous halloysite (HNT) and octadecyl modified montmorillonite (MMT) nanoclay as well as two types of essential oils, orange (OO) and thyme oil (TO). The characterization was performed by elemental analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and gas chromatography (GC) analysis. FTIR confirmed that both clays adsorbed the EOs. The DRX and TGA results showed that MMT clay showed higher thyme oil adsorption and better interactions than with orange oil. The Clay/EO composites encapsulated in Polyethylene/tie/Polyamide/tie/Polyethylene multilayer film showed a continuous aroma release for longer periods. It was found that the Polyamide (PA) barrier layer thickness had has an effect on the liberation of the volatile compounds through the multilayer film. On the other hand, the highest cymene aroma release at 72 h was 800 μg for the MMT clay/thyme oil encapsulated in the multilayer film with lower PA layer thickness. This multilayer film encapsulated clay/EO composites could be an option to prepare aroma-controlled release systems for pest control and food packaging applications as antimicrobial or fungicidal systems.

Different mixing methods were used for the fatty acid modification of magnetite nanoparticles. The magnetite nanoparticles were dissolved in ethanol with a previously dissolved oleic or stearic acid solution. The mix was then homogenized and washed to eliminate the unreacted fatty acid. The modified nanoparticles were FTIR analysis confirmed that the modified nanoparticles presented the characteristic groups of the fatty acids. The vibrating sample magnetometer analysis (VSM) showed a very slight decrease in the magnetic properties of the magnetite, from 88.7 to 53.7 emu/g, which obviously was due to the presence of the fatty acids. TGA showed that the fatty acid modification degree of the magnetite was less than that reported elsewhere, nonetheless, during the precipitation tests in toluene; it was observed that the modification was sufficient to maintain the stability of the dispersion without affecting the magnetic properties. Additionally, TEM micrographs showed that the modified magnetite nanoparticles formed a cluster, with the fatty acids surrounding the magnetite nanoparticles. Confirming that the fatty acid layer was deposited as monolayers on the magnetite particle surface of approximately 2 nm in thickness with OA and 2.3 nm with SA. It was observed that the use of the two fatty acids produced inter-digitation among the fatty acids. Finally, nanocomposites based on liquid silicone rubber (LSR) were prepared with modified and unmodified magnetite and their rheological and magnetic behavior was studied. This fatty acid modification of magnetite particles improved the dispersion and distribution of modified particles into the silicon matrix.

A work was carried out in order to obtain a TPV based on HDPE and EPDM, studying the effect of three different peroxides. The effect of one mono- and two bifunctional peroxides was studied. In general, at equal wt% of peroxide, the bifunctional peroxides produced greater gel content, higher tensile stress, and higher elongation at break. Thereafter, the work was focused on studying the effect of this TPV, as well as a commercial TPO, on the tensile and flame retardant properties of composites based on blends of HDPE and a thermoplastic elastomer (either TPV or TPO), plus 130 phr of magnesium hydroxide (MH). The composites without the rubbery phase, but with 130 phr of MH, were highly brittle and fragile. The composites with the rubbery phase, on the other hand, (either TPO or TPV), were tougher and presented relatively much higher tensile properties. With regard to flame retardancy, the formulations containing the TPV showed better flame retardancy and passed as V-1 in the UL-94V. With respect to the cone calorimeter, those with TPO or TPV all generated a total of 80 MJ of heat energy. The compositions with TPV, however, generated this amount of heat over a larger period of time, i.e., showing less heat generated per second. In addition, the compositions with TPV presented a markedly lower pHRR, by an average of 15%. Thermogravimetric analysis (TGA) showed that the MH in the samples with a 40 wt% rubbery phase starts decomposing at 315°C. However, as the temperature increases, the MH in the TPV composite apparently decomposes at a slower rate than that in the TPO composite.

The performance of Polyethylene (PE)/Clay/Silver nanocomposites is dependent to a great extent on the properties of filler–matrix interface. To improve the interfacial properties in PE/Clay/Silver composites, different types of compatibilizers or adhesion promoters were introduced. The compatibilization provided by maleic anhydride (MA), itaconic acid (IA) and 2-[2-(dimethylamine)-ethoxy] ethanol (DMAE) functionalized PEs for forming PE-based nanocomposites was studied and compared. IA was grafted into PE by melt mixing to obtain PEgIA (compatibilizer 1), thereafter, PEgIA and PEgMA (compatibilizer 2) were reacted with DMAE also by melt mixing to obtain PEgI-DMAE (compatibilizer 3) and PEgM-DMAE (compatibilizer 4). These compatibilizers were reacted using ultrasound with a solution of AgNO3 0.04 M and ethylene glycol. Ammonium hydroxide was added in a ratio of 2:1 M with respect to silver nitrate. These silver coated compatibilizers were mixed with PE and with a quaternary ammonium modified montmorillonit...

Nanocomposites based on cyclic olefin copolymer/linear low density polyethylene blends (COC/LLDPE) with various contents of three different modified organoclays (20A, 10A, and I28E) compatibilized with polyethylene grafted maleic anhydride (PEgMA) were prepared by met mixing. The influence of content and type of organoclay and compatibilizer on nanocomposite morphology, thermal, and mechanical properties as well as on oxygen and water vapour barrier properties was determined. X-ray diffraction (XRD) and transmission microscopy (TEM) were used to investigate the clay dispersion, which showed a strong dependence on compatibilizer and type of organoclay. An exfoliated–intercalated morphology was obtained for compatibilized samples of C20A and I28E organoclays at 5 wt%. A less intercalated structure was obtained for samples with C10A. The exfoliated–intercalated structure was influenced both by the compatibilizer and the increase on the nanocomposite viscosity due to the COC incorporation as was determined by Rheological measurements. Mechanical analysis gave an evidence of increasing stiffness after nanoclay was added into COC/LLDPE blend matrix observing higher Young modulus for the compatibilized samples. A notorious decrease of Oxygen and Water vapour permeation rate was observed for COC/LLDPE blend films nanocomposites only when using C20A and I28E clays. These results can be useful in the design of sustainable flexible films for the packaging requirements of specific types of food. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

In this study, we present a study of polypropylene/bentonite composites where stearic acid was used as both a surface and interface modifier during the compounding of composites. The concentration of bentonite was 1.5, 2.5, 5.0, and 10 parts per hundred. The composites were characterized by impact resistance and tensile tests, rheological analysis, the dispersion state of the filler observed by optical microscopy, and interaction between bentonite and stearic acid, as analyzed by Fourier transform infrared spectroscopy. No chemical interaction was found between bentonite and stearic acid. Composites with modified bentonite and stearic acid used as interface modifiers increased the elongation at break; these samples also showed better dispersion of the filler in comparison with the other compounds. In addition, stearic acid acted as a lubricant, favoring the interaction of the polymer with the filler and decreasing the viscosity of the compounds. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42264.

Polyethylene grafted with maleic anhydride (PEgMA) was used as one type of compatibilizer and it was reacted by reactive extrusion with 2 [2 (dimethyl-amine) ethoxy] ethanol (DMAE) to obtain other type of compatibilizer PEgDMAE. Synthesis and deposition of silver nanoparticles (Ag-NP) was done by two different methods: In one method (method A), silver nanoparticles were synthetized using ethylene glycol (EG) and pre mixed with compatibilizers using ultrasound with the aim of inducing an interaction between AgNP and polar groups of compatibilizer. Then they were incorporated in a blend with PE and Clay by melt mixing. In other method (method B) silver nanoparticles, were synthetized using EG, premixed with the Clay in a solvent suspension, and then incorporated with PE and compatibilizers. Characterization techniques indicated that an increase in the content of Ag-NPs, filler dispersion (clay and silver), mechanical and antimicrobial properties were strongly affected by the type and concentration of the compatibilizer and preparation method used. The using of PEgDMAE resulted in a better particle distribution of both sliver and clay into PE. The obtained nanocomposites showed enhanced mechanical and antimicrobial properties with highly exfoliated and dispersed filler into the PE matrix that offers a better option for obtaining hybrid nanocomposites for different applications.

The effect of using a compatibilizer, such as maleic anhydride grafted polyethylene (PEgMA), on the flame retardancy and mechanical (tensile) properties of HDPE nanocomposites with silane modified Mg(OH)2 was studied. The silane modification of Mg(OH)2 was confirmed by FTIR. Filler dispersion was characterized by scanning electron microscopy in transmission mode (STEM) and the effect of filler on mechanical properties was also evaluated. The flame retardant properties were evaluated by flammability tests (Underwriters Laboratory – UL-94) and cone calorimeter. The mechanism by which the use of PEgMA compatibilizer improves the flame retardancy of HDPE/Mg(OH)2 was studied. Through the simultaneous TGAIR analysis, it was found that when using PEgMA, the flame retardant properties of HDPE/Mg(OH)2 are modified, due to the generation of volatile compounds in the thermal decomposition.