Preparation of multiphase poly(styrene-co-butyl acrylate)/wax-clay nanocomposites via miniemulsion polymerization

In the presence of different wax-clay nanocomposites concentrations, poly(styrene-co-butyl acrylate) P(S-co-BA) copolymers were prepared via free-radical random copolymerization of styrene and butyl acrylate in miniemulsion. Wax-clay nanocomposites were obtained through ultrasonic mixing at a temperature above the melting point of the wax at different clay loadings (1, 5, 7 and 10 wt%). The main objectives of this study were to obtain a good exfoliation of the clay platelets in the paraffin wax. The obtained wax-clay nanocomposites were then used as filler in the preparation of P(S-co-BA)/wax-clay nanocomposites via miniemulsion polymerization. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the clay platelets were mostly exfoliated in the paraffin wax at low concentrations, and partially exfoliated at high concentrations. The particles morphology of the P(S-co-BA)/wax-clay nanocomposite latexes was mainly determined by TEM, and the wax-clay nanocomposites were found to be encapsulated inside the P(S-co-BA) particles and that core/shell morphology was obtained. The morphology of the P(S-co-BA)/wax-clay nanocomposites (after film formation) ranged from exfoliated to intercalated structures, depending on the percentage of wax-clay nanocomposites loading. The impact of the wax-clay loading on the thermal stability and the thermo-mechanical properties of the final polymer wax-clay nanocomposites were determined

Dielectric sensitization of zeolitic imidazolate framework-8 (ZIF-8) nanopowder.

Metallo-organic complexes are a class of materials that are increasingly used in sensory applications. Zeolitic imidazolate frameworks (ZIFs) are their subclass that are topologically isomorphic with zeolites. The porosity of the crystals and their chemical structure, as well as their thermal and chemical stability, make some of these materials (ZIFs) very suitable for making sensors. The large specific area of micro and nano particles is an important parameter for sensor applications. Despite the fact that the dielectric characterization of powders in the RF domain was neglected in scientific works, this method can have great practical importance. This paper presents the results of the dielectric characterization of the ZIF-8 nanopowder in the frequency range of 24 Hz to 24 KHz. The results indicate that the presence of evaporation of water, ethanol and methanol leads to major changes in the dielectric permittivity of ZIF-8 nanopowder

Isothermal Crystallization Kinetics and Morphology of Double Crystalline PCL/PBS Blends Mixed with a Polycarbonate/MWCNTs Masterbatch

In this work, the 70/30 and 30/70 w/w polycaprolactone (PCL)/polybutylene succinate (PBS) blends and their corresponding PCL/PBS/(polycarbonate (PC)/multiwalled carbon nanotubes (MWCNTs) masterbatch) nanocomposites were prepared in a twin-screw extruder. The nanocomposites contained 1.0 and 4.0 wt% MWCNTs. The blends showed a sea-island morphology typical of immiscible blends. For the nanocomposites, three phases were formed: (i) The matrix (either PCL- or PBS-rich phase depending on the composition), (ii) dispersed polymer droplets of small size (either PCL- or PBS-rich phase depending on the composition), and (iii) dispersed aggregates of tens of micron sizes identified as PC/MWCNTs masterbatch. Atomic force microscopy (AFM) results showed that although most MWCNTs were located in the PC dispersed phase, some of them migrated to the polymer matrix. This is due to the partial miscibility and intimate contact at the interfaces between blend components. Non-isothermal differential scanning calorimetry (DSC) scans for the PCL/PBS blends showed an increase in the crystallization temperature (Tc) of the PCL-rich phase indicating a nucleation effect caused by the PBS-rich phase. For the nanocomposites, there was a decrease in Tc values. This was attributed to a competition between two effects: (1) The partial miscibility of the PC-rich and the PCL-rich and PBS-rich phases, and (2) the nucleation effect of the MWCNTs. The decrease in Tc values indicated that miscibility was the dominating effect. Isothermal crystallization results showed that the nanocomposites crystallized slower than the neat blends and the homopolymers. The introduction of the masterbatch generally increased the thermal conductivity of the blend nanocomposites and affected the mechanical properties.Thandi P. Gumede was financially supported by the National Research Foundation and the Sasol Inzalo Foundation in South Africa, while the POLYMAT/UPV/EHU team was funded by the following projects: “UPV/EHU Infrastructure: INF 14/38”; “Mineco/FEDER: SINF 130I001726XV1/Ref: UNPV13–4E–1726” and MINECO MAT2017-83014-C2-1-P. The publication of this article was funded by the Qatar National Library

Influence of the Ce :YAG amount on structure and optical properties of Ce :YAG-PMMA composites for white LED

Ce:YAG-poly(methyl methacrylate) (PMMA) composites were prepared by using a melt compounding method, adding several amounts of Ce:YAG in the range 0.1–5wt.%. The optical properties of the obtained composites and of the composites combined with a blue LED were measured to investigate the effect of the amount of Ce:YAG on the resulting emitted light in view of possible application in white LED manufacture. An increase in Ce:YAG amount caused an increase in the emission and a shift of 15 nm, influencing the white LED performance. The structure and morphology of the composites were studied. The results show that the interaction between the two components, observed by using solid state NMR experiments, are the responsible for the observed shift.The authors acknowledge the University of Palermo, FFR 2012–2013 –ATE 0594 and CORI201

Isothermal Crystallization Kinetics and Morphology of Double Crystalline PCL/PBS Blends Mixed with a Polycarbonate/MWCNTs Masterbatch

Published ArticleIn this work, the 70/30 and 30/70 w/w polycaprolactone (PCL)/polybutylene succinate (PBS) blends and their corresponding PCL/PBS/(polycarbonate (PC)/multiwalled carbon nanotubes (MWCNTs) masterbatch) nanocomposites were prepared in a twin-screw extruder. The nanocomposites contained 1.0 and 4.0 wt% MWCNTs. The blends showed a sea-island morphology typical of immiscible blends. For the nanocomposites, three phases were formed: (i) The matrix (either PCL- or PBS-rich phase depending on the composition), (ii) dispersed polymer droplets of small size (either PCL- or PBS-rich phase depending on the composition), and (iii) dispersed aggregates of tens of micron sizes identified as PC/MWCNTs masterbatch. Atomic force microscopy (AFM) results showed that although most MWCNTs were located in the PC dispersed phase, some of them migrated to the polymer matrix. This is due to the partial miscibility and intimate contact at the interfaces between blend components. Non-isothermal di erential scanning calorimetry (DSC) scans for the PCL/PBS blends showed an increase in the crystallization temperature (Tc) of the PCL-rich phase indicating a nucleation e ect caused by the PBS-rich phase. For the nanocomposites, there was a decrease in Tc values. This was attributed to a competition between two e ects: (1) The partial miscibility of the PC-rich and the PCL-rich and PBS-rich phases, and (2) the nucleation e ect of the MWCNTs. The decrease in Tc values indicated that miscibility was the dominating e ect. Isothermal crystallization results showed that the nanocomposites crystallized slower than the neat blends and the homopolymers. The introduction of the masterbatch generally increased the thermal conductivity of the blend nanocomposites and a ected the mechanical properties

Glycogen and gold nanoparticle bioconjugates: controlled plasmon resonance via glycogen-induced nanoparticle aggregation

Hybrid nanosystems composed of glycogen biopolymers and gold nanoparticles were prepared by an in situ non-toxic synthetic procedure. Transmission electron microscopy (TEM) and various spectroscopic methods (optical absorption, X-ray photoelectron and photoluminescence spectroscopy) were used for the characterization of the obtained bioconjugates. The gold nanoparticles formed in the presence of glycogen were spherical in shape and approximately 15 nm in diameter. The TEM micrographs show that the nanoparticles aggregated on the surface of the glycogen biomolecules. This effect induced a shift of the surface plasmon resonance band towards higher wavelengths on an increase in gold ion concentration. Effective medium theory calculations were carried out in order to explain the observed redshift of the plasmon band in the absorption spectra of the Au-glycogen colloids. The interactions of the gold nanoparticles with glycogen strongly affected the photoluminescence of the glycogenin protein incorporated into its structure. The Au-glycogen hydrocolloids exhibited good chemical stability in the presence of saline, phosphate buffered saline, alanine, histidine and D-glucose

Electrospun polylactic acid/date palm polyphenol extract nanofibres for tissue engineering applications

In this study, a set of polylactic acid (PLA)/polyphenol extracted from date palm fruit (DP) blends were prepared by electrospinning process to be used as cell culture scaffolds for tissue engineering applications. For this purpose, PLA/DP blends with variable composition were dissolved in dichloromethane/dimethylformamide (70:30, v/v) mixture and then electrospun to obtain the fibres. Contact angle measurements, dynamic mechanical analysis, mechanical tensile and scanning electron microscopy (SEM) tools were used to study the physico-mechanical properties of the electrospun scaffolds. The results revealed that scaffolds became more hydrophilic with addition of DP. Increasing the polyphenol concentration caused the tensile strength and Young's modulus to decrease. The SEM graphs indicated a decrease in fibre diameter with increasing DP content. In addition, it was found that both cell proliferation and cell viability were enhanced with increased DP concentration within the scaffolds. The scratch test shows that there is an enhancement in cell migration through the scratch for PLA/DP scaffolds; again, higher DP content resulted better migration. Our results suggest that improved mechanical properties, decreased fibre diameter and enhanced hydrophilicity with addition of DP improved cell migration and cell adhesion for the scaffolds. Overall, these results demonstrate that DP is a potential natural cell-friendly product for tissue engineering applications such as tissue regeneration or wound healing assays

Computational studies for the effective electrical conductivity of Copper powder filled LDPE/LLDPE composites

486-493The effective electrical conductivity (EEC) of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) polymer composites filled with copper has been studied. The nonlinear behavior has been observed for effective electrical conductivity versus filler content. Several approaches have been described to predict the electrical conductivities of polymer composites. EEC is described by artificial neural network (ANN) and it demonstrates the accurate match of experimental data for EEC with different training functions (TRAINOSS, TRAINLM, TRAINBR, TRAINSCG, TRAINBFG, and TRAINRP). The ANN approach satisfied the experimental data for EEC of polymer composites reasonably well. The complex structure encountered in LDPE/Cu and LLDPE/Cu, along with the difference in the EEC of the components, make it difficult to estimate the EEC exactly. This is the reason for which artificial neural network has been employed here. By using ANN approach experimental results indicate that EEC of polymer composites increases with increasing filler content at the same concentration

Synthesis, characterization, and antimicrobial properties of novel double layer nanocomposite electrospun fibers for wound dressing applications

Herein, novel hybrid nanomaterials were developed for wound dressing applications with antimicrobial properties. Electrospinning was used to fabricate a double layer nanocomposite nanofibrous mat consisting of an upper layer of poly(vinyl alcohol) and chitosan loaded with silver nanoparticles (AgNPs) and a lower layer of polyethylene oxide (PEO) or polyvinylpyr- rolidone (PVP) nanofibers loaded with chlorhexidine (as an antiseptic). The top layer containing AgNPs, whose purpose was to protect the wound site against environmental germ invasion, was prepared by reducing silver nitrate to its nanoparticulate form through interaction with chitosan. The lower layer, which would be in direct contact with the injured site, contained the antibi- otic drug needed to avoid wound infections which would otherwise interfere with the healing process. Initially, the upper layer was electrospun, followed sequentially by electrospinning the second layer, creating a bilayer nanofibrous mat. The morphology of the nanofibrous mats was studied by scanning electron microscopy and transmission electron microscopy, showing successful nanofiber production. X-ray diffraction confirmed the reduction of silver nitrate to AgNPs. Fourier transform infrared spectroscopy showed a successful incorporation of the material used in the produced nanofibrous mats. Thermal studies carried out by thermogravi- metric analysis indicated that the PVP–drug-loaded layer had the highest thermal stability in comparison to other fabricated nanofibrous mats. Antimicrobial activities of the as-synthesized nanofibrous mats against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were determined using disk diffusion method. The results indicated that the PEO–drug-loaded mat had the highest antibacterial activity, warranting further attention for numerous wound-healing applications.QUST-CAS-SPR-14\15-

Effect of synthetic antioxidants on the oxidative stability of biodiesel

Biodiesels were prepared using base catalyzed methanolysis of sunflower, soybean and canola oils. Rancimat oxidative stability measurements showed that the induction period (IP) for neat canola biodiesel conformed to EN 14214, the European specification for biodiesel (IP > 6 h). Stability was enhanced when 0.5 wt.% of the synthetic antioxidants di-tert-butylhydroquinone (DTBHQ) or poly(1,2-dihydro- 2,2,4-trimethylquinoline) (Orox PK) was added. Soybean-based biodiesel spiked with 0.5 wt.% DTBHQ also reached this specification. Orox PK improved the stability of sunflower biodiesel but the 3 h induction period specified by ASTM D-6751 could not be reached. Curiously, canola biodiesel was destabilized on adding the antioxidant Naugard P (tris(nonylphenyl) phosphite).The Institutional Research Development Programme (IRDP) and the THRIP program of the Department of Trade and Industry and the National Research Foundation of South Africa, Ltd as well as Xyris Technology.http://www.elsevier.com/locate/fuelai201