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[EN] Nanocomposites of unmodified kaolinite (Kaol)/ethylene-vinyl alcohol copolymer (EVOH) with different Kaol contents have been obtained by a two-step process: melt blending in an internal mixer and film processing by co-extruding the obtained clay polymer nanocomposites pellets in between two low-density polyethylene (LDPE) layers. The addition of the clay mineral to the molten polymer has been carried out by using a Kaol/EVOH masterbatch containing 15 mass% Kaol. The so-obtained samples have been analysed by means of WAXS, SEM, TEM, DMA and tensile tests. Finally, barrier properties to water vapour and oxygen at two relative humidities have been assessed. Morphological analysis has revealed high degree of dispersion and distribution of the Kaol within the EVOH matrix. A considerable increase in the mechanical and in the barrier properties has been found. The present work puts forward the effectiveness of an unmodified kaolinite for obtaining ultra-high barrier clay mineral/polymer nanocomposites.

[EN] This paper shows novel formulations of nanolubricants added with multi-layer graphene (MLG), multi-layer graphene impregnated with copper (MLG-Cu), and multi-layer graphene impregnated with polyaniline (MLG-PANI) for applications in automotive engines. These nanofluids were prepared using commercial motor oil as the base fluid. The tribological properties were measured at 100 degrees C, and significant reductions were found in the coefficient of friction and wear. The concentrations used were 0.5% and 2% by weight, obtaining reductions in the friction coefficient and wear of up to 43% and 63%, respectively, in the case of motor oil with copper-impregnated graphene. All formulations of MLG, MLG-Cu, and MLG-PANI did not show any sedimentation when dispersed in engine oil, even three months after being produced. (C) 2016 Elsevier B.V. All rights reserved.

Multiwall carbon nanotubes (MWCNT) and multilayer graphene (MLG) were studied as microwave susceptor additives for polymers. Different percentages of both nanoparticles were added to polypropylene by melt compounding in order to study the microwave absorption and the polymer heating. Polypropylene was selected as polymer matrix due to its unpolar nature to avoid the influence of polymer polarity and evaluate the influence of the nanoparticles. Electrochemical spectroscopy impedance measurements were carried out to evaluate the conductive and dielectric properties of nano composites. Results showed that nanocomposites with higher electrical conductivity have better capacity of absorbing microwave radiation. High values of permittivity and loss tangent also increases the microwave radiation absorption and the ability of the material to convert this electromagnetic radiation into heat. Carbon nanotubes showed better microwave susceptor behavior than graphene multilayer. Nanocomposites with 1% w/w of carbon nanotubes can be compared with the heating efficiency of a polypropylene filled with 10% w/w of multilayer graphene. The higher efficiency of carbon nanotubes it is explained by their higher electrical conductivity and optimal dielectric properties of the nanocomposites compared to multilayer graphene polymer systems.

Due to its use, a large amount of Oxytetracycline (OTC) is released into water, which has a detrimental impact on aquatic ecosystems and human health. Although there are different physicochemical methods (mainly photodegradation) to remove OTC, there is increasing interest in the use of bioremediation. The sorption characteristics of OTC using living and dead biomass of the microalga Phaeodactylum tricornutum have been investigated in this study. Kinetics, isotherms and maximum elimination capacity were tested and discussed. Kinetic studies showed that the OTC removal by living biomass followed a sigmoidal model. However, the dead biomass followed a pseudo-first order model. The living biomass showed higher efficiency than the dead biomass with maximum sorption capacities of 29.18 mg g−1 and 4.54 mg g−1, respectively. Combination of living biomass and photodegradation under the culture conditions eliminated 13.2 mg L−1 of OTC during 11 h of culture and with an initial OTC concentration of 15 mg L−1. With an initial OTC concentration of 2.5 mg L−1, 97% of OTC was removed. This removal was mainly caused by bioremediation than by photodegradation. The results proved the potential practical application of the living P. tricornutum biomass for a low-cost and efficient removal of OTC from seawater.

The processing and characterization of biodegradable nanocomposites based on poly(ester-urethane) reinforced with different amounts (0.5, 1 and 3 wt %) of nanosized hydroxyapatite (nHA) are reported. The selected poly(ester-urethane) was synthesized starting from a tri-block copolymer based on poly(epsilon-caprolactone) (PCL) and poly(L-lactic acid) (PLLA). The nanocomposites were prepared by extrusion and by press molding. Several techniques were applied to investigate the properties of the nanocomposites. Electron microscopy revealed that the poly(ester-urethane) matrix is able to phase separate and that the addition of well-dispersed nanofillers modifies the dimension of the segregated phase. The thermal stability of the PU matrix, regulated by the PLLA block, decreased when low contents of nHA (0.5 and 1 wt %) were added, even if the thermal stability of the PCL-block was increased for each nHA amount. The good mechanical response of the nanocomposites confirmed the absence of agglomerates in the dispersion of the nanofillers in the polymeric matrix. The nHA presence also increased the surface hydrophilicity. Furthermore, rheology measurements, mechanical and thermal tests demonstrated the different behavior induced by the addition of nHA in different amounts. In fact, nHA acts as plasticizer at low concentrations (0.5, 1 wt %) and as reinforcement at a higher nHA amount (3 wt %). In vitro degradation tests were performed using a phosphate buffer solution. The results reported here are relevant for the development of nanocomposites based on a biodegradable and biocompatible polymeric matrix reinforced with small amounts of biocompatible nanofillers for different applications, especially in the biomedical field. (C) 2015 Elsevier Ltd. All rights reserved.

Novel polyelectrolyte membranes were prepared from pure solutions of alginate (Alg), carrageenan (Car) and their mixtures. The films were crosslinked and sulfonated and then, characterized by several techniques: ionic exchange capacity (IEC), water uptake, mechanical thermal properties, and also functional properties such as methanol permeability and proton conductivity. The results show that Alg/ Car membranes have a ductile behavior. Low carrageenan concentrations have a weak thermoprotective effect, which slightly delays both T-g and T-m of prepared membranes. The methanol permeability of Alg/ Car membranes increase with the carrageenan content varying from 0.55 x 10-6 cm(2) s(-1) for Alg/Car 100/ 00 to 4.89 x. 10-6 cm(2) s(-1) for Alg/Car 80/20. The Proton conductivities of the membranes increase with the carrageenan content from 9.79 x 10(-3) S cm(-1) for Alg/Car 100/00 until 3.16 x 10(-2) S cm(-1) for Alg/Car 80/20 at 90 degrees C. Finally the proton transfer mechanism is discussed in terms of the conductivity activation energy and the dependence of the proton diffusion coefficient with the temperature has been studied.

[EN] Aligned mats of poly(lactic acid) (PLA) nanofibers containing nanosized hydroxyapatite filler have been obtained via electrospinning onto a rotating mandrel. Their structure and morphology have been characterized as a function of the production parameters, by SEM, DSC, DMA and WAXS, with emphasis in the effects of the take-up velocity. SEM, DSC and X-ray diffraction studies confirmed a reduction in fiber diameter, an increase of fiber orientation and a highly crystalline structure of the mats collected at higher speed due to the stretching produced during the process. Double melting behavior was observed, suggesting the presence of two crystalline forms. Moreover the higher storage modulus (E¿ modulus), and glass transition temperatures of the higher speed collected mats were correlated with an enhancement in the thermal stability and nanofiller distribution. © 2012 Elsevier Ltd. All rights reserved.

[EN] Amorphous PLA nanocomposites based on organic modified kaolinite (KAO) and montmorillonite (MONT) at 4 wt.% were prepared by melt blending and then biodegraded in compost. All materials showed effective degradation in this medium, according to visual observations, DSC and FTIR analysis. The addition of nanoclays was found to increase the PLA degradation rate, especially for kaolinite, due to the presence of hydroxyl groups belonging to the silicate layers of these clays. Addition of MONT to PLA also has a catalytic effect on polymer degradation in compost, but only in the last stages of degradation. In the early stages, MONT tends to delay the degradation of PIA probably due to its higher dispersion level into the polymer matrix as compared to KAO, creating a barrier effect of MONT layers towards water hydrolysis on PLA ester groups.

[EN] Composites of thermoplastic polyurethane (TPU) and ultra-thin graphite (UTG) with concentrations ranging from 0.5 wt.% to 3 wt.% were prepared using a solution compounding strategy. Substantial reinforcing effects with increased loadings are achieved. Compared to neat TPU, values for storage modulus and shear viscosity are enhanced by 300% and 150%, respectively, for UTG concentrations of 3 wt.%. Additionally, an enhancement of thermal properties is accomplished. The crystallization temperature and thermal stability increased by 30 C and 10 C, respectively, compared to neat TPU. Furthermore, the use of oxidized UTG (UTGO) with its added functional oxygen groups suggests the presence of chemical interactions between UTG and TPU, which additionally impact on the thermal properties of the corresponding composites. Controlling the oxidation degree, thus offers further possibilities to obtain composites with tailored properties. The presented approach is straightforward, leads to homogeneous TPU-UTG composites with improved materials properties and is especially suitable for commercial UTG materials and further up-scaled production.

The electrospinning approach is an easy and useful method to fabricate porous supports with tailored properties for the preparation of impregnated membranes with enhanced characteristics. Therein, this technique was used to obtain polyvinyl alcohol (PVA) nanofiber mats in which Nafion (R) polymer was infiltrated. These Nafion/PVA membranes were characterized in their mechanical properties, proton conductivity and fuel cell performance. Conductivity of the composite membranes was below the showed by pristine Nafion (R) due to the non-ionic conducting behaviour of the PVA phase, although the incorporation of the PVA nanofibers strongly reinforced the mechanical properties of the membranes. Measurements carried out in a single cell fed with H-2/Air confirmed the high performance exhibited by a 19 mu m thick nanofiber reinforced membrane owing to its low ionic resistance. These reasons make ultrathin (<20 mu m) Nafion/PVA composite membranes promising candidates as low cost ion-exchange membranes for fuel cell applications.

The marine diatom Phaeodactylum tricornutum Bohlin was exposed to different cadmium concentrations (1–100 mg l−1) for 4 days. The amount of cadmium removed was recorded, with particular attention paid to long-term uptake kinetics, and to the cellular location of cadmium. Cadmium accumulation occurred at all concentrations assayed. The EC50 of cadmium to P. tricornutum was 22·39 mg l−1 after 4 days of exposure. Cadmium uptake followed a saturation kinetic at cadmium concentrations ≥25 mg l−1. However, at lower cadmium concentrations, the uptake of this metal followed a linear trend for all days of culture. At cadmium concentrations in the medium lower than 25 mg l−1, P. tricornutum removed cadmium mainly within the cell. At higher cadmium concentrations, the amount of cadmium removed by adsorption to the cell surface was higher than intracellular cadmium, because of the toxic effects of cadmium on P. tricornutum cells. This toxicity reduced the cadmium accumulation within the cells.

An optimization strategy for the separation and analysis of class III metallothioneins from a complex matrix by capillary zone electrophoresis (CZE) is presented and illustrated. Metallothioneins are a group of polypeptides used for many organisms to alleviate stresses imposed by exposure to heavy-metal excess. The analysis requires several steps: chromatography on exclusion or anion-exchange columns, ultrafiltration and HPLC with derivatization. In the present paper, a rapid and simple separation technique by CZE with an uncoated polyimide-clad fused-silica capillary is described. This technique permits the analysis of these molecules without prior steps of purification and derivatization. The running conditions were voltage −12 kV, room temperature and 150 mM sodium phosphate buffer (pH 3.5). Based on this preliminary study, CZE with an uncoated fused-silica capillary using sodium phosphate buffer appears to be a useful technique for the separation of class III metallothioneins.

Essential heavy metals, as copper, can be toxic for microalgae at high concentrations. Copper affected growth and other parameters closely related to photosynthesis of the marine diatom Phaeodactylum tricornutum. A copper concentration of 0.10 mg l−1 provoked about 50% growth reduction and 1 mg l−1inhibited the growth. Copper also interfered with photosynthesis and ATP production. A copper concentration of 0.5 mg l−1 reduced in a 50% the photosynthetic rate. Therefore, growth is more affected by copper than photosynthesis. Results of chlorophyll a fluorescence obtained by flow cytometry showed that copper's inhibitory effect on PS II activity is located on its oxidizing side. The lower copper concentration assayed provoked a significant decrease in the cellular pool of ATP. Pigment analysis by HPLC showed that copper affected the pigment pattern of P. tricornutum. Important changes were observed for chlorophyll a and its allomer: chlorophyll a proportion decreased while its allomer increased with the copper concentration, being maximum at 1 mg Cu l−1. The study of the intracellular pH by flow cytometry revealed that P. tricornutumcells exposed to 0.5 and 1 mg Cu l−1 showed an intracellular pH higher than control cultures cells, explaining the high proportion of the chlorophyll a allomer in these cells.