Evaluation of polyesters from renewable resources as alternatives to the current fossil-based polymers. Phase transitions of poly(butylene 2,5-furan-dicarboxylate)

Poly(butylene 2,5-furan dicarboxylate) (PBF) is an alipharomatic polyester that can be prepared using monomers derived from renewable resources such as 2,5-furan dicarboxylic acid and 1,4-butanediol. In the present work the thermal behavior of PBF was studied. Multiple melting was observed during heating traces of samples isothermally crystallized from the melt using differential scanning calorimetry (DSC). The wide angle X-ray diffraction (WAXD) patterns did not reveal the presence of a second crystal population, or a crystal transition upon heating. DSC study showed that the phenomena are closely related to recrystallization. Temperature modulated DSC (TMDSC) tests indeed evidenced enhanced recrystallization. The equilibrium melting point was estimated to be 184.5 °C using the linear Hoffman–Weeks extrapolation. The heat of fusion of the pure crystalline polymer was found equal to 129 J/g or (27.35 kJ/mol), a little lower than that of PBT. The Lauritzen–Hoffman secondary nucleation theory was used and the surface energy values and the work of chain folding were found to be comparable to those of PBT, but quite lower than those of poly(ethylene terephthalate) (PET). The non-isothermal crystallization on cooling and the cold-crystallization of quenched samples were also studied. Condensed spherulites were observed on isothermal crystallization under large supercoolings by using polarized optical microscopy (POM), while the spherulites turned to ring-banded morphology at higher temperatures. In every case the nucleation density was high.     

Effects of benzoyl peroxide on some properties of composites based on hemp and natural rubber

The obtaining and characterization of polymer composites based on natural rubber and hemp, in which the elastomer crosslinking has been achieved with benzoyl peroxide, are presented. The mechanical characteristics, gel fraction, crosslink density, water uptake swelling parameters and FTIR of the composites based on natural rubber and hemp fiber vulcanized by dibenzoyl peroxide have been investigated as a function of the hemp content. The hardness, modulus at 100 % elongation, tearing strength, tensile strength and elongation at break have been improving with the increasing of fiber content in composites materials due to the better interaction of fiber in natural rubber composites. These results indicate that hemp has a reinforcing effect on natural rubber. Gel fraction value is over 95 % for all blends and varies irregularly depending on the amount of hemp in the composites. The crosslinking density (ν) of samples increases as the amount of hemp in blends increases, because hemp act as a filler in natural rubber blends and leads to reinforcement of the blends. The water uptake and swelling parameters also increases with the increasing of the amount of fiber content, because of the hemp hydrophilic characteristics.     

Role of Methyl Salicylate on Oviposition Deterrence in Arabidopsis thaliana

Plants attacked by herbivores have evolved different strategies that fend off their enemies. Insect eggs deposited on leaves have been shown to inhibit further oviposition through visual or chemical cues. In some plant species, the volatile methyl salicylate (MeSA) repels gravid insects but whether it plays the same role in the model species Arabidopsis thaliana is currently unknown. Here we showed that Pieris brassicae butterflies laid fewer eggs on Arabidopsis plants that were next to a MeSA dispenser or on plants with constitutively high MeSA emission than on control plants. Surprisingly, the MeSA biosynthesis mutant bsmt1-1 treated with egg extract was still repellent to butterflies when compared to untreated bsmt1-1. Moreover, the expression of BSMT1 was not enhanced by egg extract treatment but was induced by herbivory. Altogether, these results provide evidence that the deterring activity of eggs on gravid butterflies is independent of MeSA emission in Arabidopsis, and that MeSA might rather serve as a deterrent in plants challenged by feeding larvae.     

Synthesis of ternary zinc spinel oxides and their application in the photodegradation of organic pollutant

Ternary zinc spinel oxides such as Zn₂SnO₄, ZnAl₂O₄ and ZnFe₂O₄ were synthesized and characterized, and their activities in the photodegradation of phenol molecules were investigated. Zn₂SnO₄, ZnAl₂O₄ and ZnFe₂O₄ powders were synthesized by hydrothermal, metal–chitosan complexation and solvothermal routes, respectively. The face-centered cubic spinel structure of each material was confirmed by powder X-ray diffractometry (XRD) and its porous structure by N₂ adsorption–desorption isotherms. The characterization of spinels was complemented with Fourier transform infrared spectroscopy (FTIR) and X-rays fluorescence (XRF), revealing the formation of spinel structures with high purity. The photocatalytic activity in the degradation of phenol was observed only with Zn₂SnO₄ oxide. Mineralization degree of phenol molecules by Zn₂SnO₄ photocatalyst determined by total organic carbon analysis (TOC) reached 80% at 360 min under sunlight.     

Spray Drying of Green Corn Pulp

Maize (Zea mays) is a cereal grown in Brazil, and its availability is limited to the harvest season. An alternative processing route is based on the production of green corn powder, which has a longer shelf-life and increased versatility. This study aimed to evaluate the influence of drying conditions on the physical characteristics, size, and morphology of green corn powder. Drying experiments were performed on a spray dryer according to a central composite rotational design to evaluate inlet air temperature, feed flow rate, and pulp concentration. The yield of dried pulp corn had an average value of 36.19%. The following mean values for the physical properties of the powder were measured: solubility of 94.37 g/100 g, wettability of 128.05 seconds, moisture content of 1.97%, water activity of 0.13, density of 0.79 g/mL, and a particle diameter of 31.02 µm. The powder was also yellow with less intensity, and the particle surface was smooth at higher temperatures and had a tendency to form agglomerates. The estimated optimal conditions for spray drying were 48% (w/w) pulp concentration, 172°C inlet air temperature, and feed flow rate of 0.56 L/h.     

Isothermal crystallization kinetics and morphology of PP/TiO2 nanocomposites using titanium n‐butoxide precursor

This study investigates the influence of the addition of TiO₂, obtained by hydrolysis–condensation reaction of titanium dioxide precursors, on the kinetics of polypropylene (PP) isothermal crystallization. The dispersion of nanoparticle and its relation to the degree of crystallinity by XRD was also investigated. The results indicated that the addition of the TiO₂ increased the degree of crystallinity of PP and its crystallization temperature. Likewise, the nucleation and crystal growth processes were also affected, as indicated by the TEM morphology, the Avrami kinetic model, and the optical microscopy, in which a nucleation effect was detected. POLYM. COMPOS. 36:517–526, 2015. © 2014 Society of Plastics Engineers     

Design and realization of transparent solar modules based on luminescent solar concentrators integrating nanostructured photonic crystals

Herein, we present a prototype of a photovoltaic module that combines a luminescent solar concentrator integrating one‐dimensional photonic crystals and in‐plane CuInGaSe₂ (CIGS) solar cells. Highly uniform and wide‐area nanostructured multilayers with photonic crystal properties were deposited by a cost‐efficient and scalable liquid processing amenable to large‐scale fabrication. Their role is to both maximize light absorption in the targeted spectral range, determined by the fluorophore employed, and minimize losses caused by emission at angles within the escape cone of the planar concentrator. From a structural perspective, the porous nature of the layers facilitates the integration with the thermoplastic polymers typically used to encapsulate and seal these modules. Judicious design of the module geometry, as well as of the optical properties of the dielectric mirrors employed, allows optimizing light guiding and hence photovoltaic performance while preserving a great deal of transparency. Optimized in‐plane designs like the one herein proposed are of relevance for building integrated photovoltaics, as ease of fabrication, long‐term stability and improved performance are simultaneously achieved. © 2015 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.     

Electrochemical Performance of Nd1.95NiO4+δ Cathode supported Microtubular Solid Oxide Fuel Cells

Nd_1.95NiO_4+δ (NNO) cathode supported microtubular cells were fabricated and characterized. This material presents superior oxygen transport properties in comparison with other commonly used cathode materials. The supporting tubes were fabricated by cold isostatic pressing (CIP) using NNO powders and corn starch as pore former. The electrolyte (GDC, gadolinia doped ceria based) was deposited by wet powder spraying (WPS) on top of pre‐sintered tubes and then co‐sintered. Finally, a NiO/GDC suspension was dip‐coated and sintered as the anode. Optimization of the cell fabrication process is shown. Power densities at 750 °C of ∼40 mWcm⁻² at 0.5V were achieved. These results are the first electrochemical measurements reported using NNO cathode‐supported microtubular cells. Further developments of the fabrication process are needed for this type of cells in order to compete with the standard microtubular solid oxide fuel cells (SOFC).     

Carrier effect on structure and properties of heat-treated poly(ethylene terephthalate) fibers. I. Thermal analysis and dynamic mechanical properties

Poly(ethylene terephthalate) (PET) fibers of different draw ratios (as spun and drawn 2.8×) were submitted to different heat settings. Subsequently, they were treated in benzoic acid solutions at different concentrations and for different times of exposition. The plas-ticizing effect on the morphology of these heat-setted fibers due to the different treatments in benzoic acid solutions was studied by differential scanning calorimetry (DSC) and dynamic and mechanical thermal analysis (DMTA). The DSC experiments revealed the appearance of a premelting peak (pm1) around 130°C, when the applied heat settings were carried out for 8 h in the presence of boiling water, and around 150–160°C for the dry heat setting for 7 h at 130°C followed by 1 h in the presence of boiling water. These premelting peaks have been associated with the melting of smaller and imperfect crystals present in the amorphous region. Also, the analysis of the main melting peaks revealed that the undrawn fiber presented a wider distribution of smaller crystals than the drawn one. Their subsequent treatments in the benzoic acid solutions revealed through the DSC thermograms that this first premelting peak tends to disappear as the concentration and time of benzoic acid treatment increase. Also, a new premelting peak (pm2) appears in the DSC thermograms at temperature around 180°C. It seems that a dislocation of the pm 1 peak is occurring towards higher temperatures and is being transformed in this new premelting peak. The DMTA revealed the appearance of an α_c transition in the temperature range from 140 to 160°C and this α_c transition seems to be related to the relaxations of the new crystallities formed due to the plasticization effect of the benzoic acid. Also, the second premelting peak seems to be related to the fusion of such crystals. Therefore, a complex change in the morphology of the studied PET fibers due to the benzoic acid action has been revealed. © 1996 John Wiley & Sons, Inc.     

Characterisation of the Essential Oils of some Cultivated Aromatic Plants of Industrial Interest

The compositions of the essential oils of Rosmarinus officinalis L, Salvia lavandulifolia V and Lavandula latifolia M, obtained by steam distillation from plants cultivated in the northeast of Spain, have been studied by gas chromatography and gas chromatography/mass spectrometry. The essential oil of rosemary appears to be more complex and richer in flavour notes than other previously studied Spanish rosemary oils, and has an intermediate ratio of α-pinene and of 1,8-cineole in relation to essential oils of rosemary of different geographical origins, but higher proportions of camphor, verbenone and linalool. The essential oil of sage has proportions of 1,8-cineole, camphor, endo-borneol, trans-caryophyllene and α-humulene closer to commercial Salvia officinalis L than to other Spanish sages of different geographical locations, and the difference from commercial Salvia officinalis L is due principally to the higher ratio of terpene hydrocarbons and the lower proportion of thujone in the Spanish sage studied here. The essential oil of the spike lavender has the same main components and similar proportions as other Spanish wild and commercial spike lavender essen-tial oils, but shows differences in the nature of the minor components (rhodinol fraction).