Effects of processing parameters on the mechanical properties of polypropylene random copolymer

The mechanical properties of polypropylene random copolymer (PP-R) with different processing parameters were studied. Special attention is devoted to the investigation of the influence of masterbatch addition on the variation in the mechanical properties of injection moulded PP-R. Tensile, instrumented Charpy impact, Shore D hardness, differential scanning calorimeter (DSC) and Vicat softening temperature (VST) tests were conducted on the test samples containing different colour masterbatches varying from 0.5 to 10 wt%. The observed changes in the mechanical behaviour are explained by the type and level of masterbatch content. The natural UV weathering performance of the PP-R material was studied from the masterbatch type point of view. The effect of processing parameters on material performance was studied on samples which were directly obtained from extruded pipes and on injection moulded samples.

Finally, the effects of storage time on the polymer properties were investigated.     

The use of dsc to assess the stabilization of thermoplastic eucalyptus tar pitch fibers

During the production of pitch-based carbon fibers, oxidative thermal stabilization is an important intermediary step, because it permits the thermoplastic as-spun fibers to be rendered thermosetting. In the present work, DSC analyses are employed to assess the stabilization of eucalyptus tar pitch fibers. This is possible due to the pronounced differences noticed between DSC profiles of green and oxidized fibers, which reflect the changes that the fiber structure undergoes during stabilization. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electrical and photoelectrical behaviour of heterojunctions based on novel oligomeric metal complexes

Naringenin‐based Schiff base ligands with 4‐aminobenzoic hydrazide were obtained as a unilateral form ( L¹ ). The ligand was oligomerized by oxidative polycondensation reaction with NaOCl as an oxidant in an aqueous alkaline medium at 90 °C to form a functional oligomer ( L² ), and its transition metal complexes such as those with Cu(II), Ni(II) and Zn(II) were prepared. The monomer and the oligomeric compounds were characterized using various techniques. Optical and electrical properties of the complexes were also investigated. All compounds showed indirect band gaps and they can be accepted as being in the semiconductor class. Organic–inorganic hybrid devices were obtained using n‐Si inorganic semiconductor and the complexes. The characteristic parameters of the devices were determined using current–voltage (I–V) and capacitance–voltage measurements in the dark. Photoelectrical properties of the devices were investigated using I–V measurements under a solar simulator with an AM1.5 global filter. Copyright © 2015 John Wiley & Sons, Ltd.     

Zinc nanowires synthesized on a large scale by a simple carbothermal process

Metallic Zn nanowires have been synthesized by a new carbothermal reduction route in which ZnO and Eucalyptus sp. tar pitch were used as source materials. This simple practical procedure was capable of producing Zn nanowires in large quantities without reoxidation. This process was carried out in inert atmosphere, without vacuum or catalyst, at temperatures (800–900 °C) lower than those required in the carbothermal reduction of ZnO with graphite. A comparative study was performed using graphite that is traditionally used as a ZnO reducer, under the same experimental conditions, however, no reaction was observed. The new process involves the pyrolysis of biopitch to obtain a highly reactive coke and the reduction of ZnO with the release of Zn_(v) for the growth of Zn_(s) nanowires. The resulting Zn nanowires were characterized by X-ray diffractometry, energy-dispersive spectroscopy and scanning electron microscopy. Differential thermal analysis and thermogravimetric analysis coupled with infrared analysis techniques were used in an effort to understand the underlying mechanism and establish the best ratio biopitch/ZnO to be used. This paper presents the characterization of the as-synthesized nanowires and discusses the main reactions involved in their production.     

Positional and conformational dependence of long-range interactions in 3,16- and 3,17-androstanediones

The 5- and 5-conformations of androstane, androstan-3-one, androstan-16-one, androstan-17-one, androstane-3,16-dione and androstane-3,17-dione have been calculated by the SCF MNDO method, using full geometry optimization, in order to assess the dependence of long-range electronic interactions of the carbonyl groups on their location and on the conformation of the steroid ring system.     

Faradaic efficiency of porous electrodeposits: an application to β-Ni(OH)<Subscript>2</Subscript> films

Electrodeposition is a common technique for coating metallic or semiconducting substrates. The growth of the layers occurs through faradaic processes in which charges are transferred across the substrate-electrolyte interface. Since more than one reaction can occur simultaneously, it is important to study the faradaic efficiency (ε) associated to the growth of the desired layers and relate it to other parameters in order to optimize the process. In this work, an indirect method to determine the faradaic efficiency of electrodeposits with porosity (p) is proposed. The method was satisfactorily applied to porous β-Ni(OH)₂ films obtained by light-assisted anodic electrodeposition. These films were grown using different electrolyte concentrations (C) and temperatures (T). In this case, a direct dependence of p and ε with C and T was found.

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Complexity of molecules

Several currently used measures of the complexity of molecules, such as, for example, those by Bertz and Randic or those based on the number of spanning trees, are briefly reviewed. We also proposed as complexity measures the sum of vertex-weights and the sum of edge-weights and their variants related to partition of vertex-weights and edge-weights into classes by their numerical values. The vertex-weights considered are the squares of the vertex-degrees, and the edge-weights are products of vertex-degrees making up the edges. Comparison is made between considered complexity measures for selected molecular graphs. All considered indices increase with increasing size and cyclicity and most with increasing branching. However, they differ regarding the influence of symmetry.     

Determination of residual oil in diesel oil by spectrofluorimetric and chemometric analysis

Multivariate calibration (PLS), principal components analysis (PCA) and linear discriminant analysis (LDA), associated to synchronous spectrofluorimetry, were used to identify and quantify non-transesterified residual vegetable oil in diesel oil with the addition of 2% of biodiesel (B2). The addition of residual oil, one of the easiest ways of adultering fuel, damages engines and leads to tax evasion. Using this method, the samples of diesel oil, B2, and B2 contaminated with residual oil were classified correctly and separated into three well-defined groups. The quantification of residual oil in B2 was carried out in the 0-25% (w/w) band, RMSEC and RMSEP values ranging from 0.26 to 0.48% (w/w) and 1.6-2.6% (w/w), respectively. The method is highly sensitive and efficient to identify and quantify this type of adulterant in which 100% of the samples were correctly classified and the average relative error was approximately 4% in the range 0.5-25% (w/w).     

Thermal Study of Polyurethane Elastomers Based on Biopitch–PEG–MDI System

Polyurethanes based on biopitch and PEG of distinct molecular masses (M _w 1500, 4000 and 6000) were synthesized using polymeric MDI. Different materials were obtained through syntheses using various biopitch content and NCO/OH ratio. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) were used to determine their thermal properties. Variations of thermal stability were observed with amorphous and semicrystalline structures depending on the biopitch content and the NCO/OH ratio. This revised version was published online in July 2006 with corrections to the Cover Date.