Reactively compatibilized and dynamically vulcanized thermoplastic elastomers based on high-density polyethylene and reclaimed rubber

Melt blending was employed to prepare thermoplastic elastomer (TPE) of reclaimed rubber (RR) and high density polyethylene (HDPE). Mechanical properties of TPE samples were improved in different methods including dynamic vulcanization and reactive blending (reactive compatibilization) during melt mixing in an internal Haake mixer. The physical and mechanical properties of the TPE blends were investigated by the dynamic mechanical analysis (DMA) and tensile tests. The thermal behavior was characterized by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The phase morphology of the blends was studied by scanning electron microscopy (SEM). Experimental results showed that, both static and dynamic mechanical properties of reactively-compatibilized and dynamically-vulcanized samples improved significantly compared with the virgin samples. The effect of dynamic-vulcanization and reactivecompatibilization on the mechanical properties revealed that the Young’s modulus and storage modulus increased with both improvement methods. SEM results showed that, dynamic-vulcanization and reactivecompatibilization methods improved the distribution of RR particles in HDPE matrix. Although both methods improved the thermal and mechanical properties of the HDPE/RR blends, dynamic-vulcanization was more effective and promising approach due to the higher properties of HDPE/RR blends prepared by this method.     

Magnetically nano core–shell Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Cu(OH)<Subscript>x</Subscript>: a highly efficient and reusable catalyst for rapid and green reduction of nitro compounds

Magnetically separable nano core–shell Fe₃O₄@Cu(OH)_x with 22 % Cu content was prepared by the addition of sodium hydroxide to a mixture of CuCl₂·2H₂O and nano Fe₃O₄ in water. Characterization of the impregnated copper hydroxide was carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD) atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), value stream mapping (VSM) and Brunauer–Emmett–Teller (BET) analysis. The core–shell nanocatalyst exhibited the excellent catalytic activity toward reduction of various nitro compounds to the corresponding amines with NaBH₄. All reactions were carried out in H₂O (55–60 °C) within 3–15 min to afford amines in high to excellent yields. Reusability of core–shell Cu(OH)_x catalyst was examined 9 times without significant loss of its catalytic activity.     

Semi-automated salt-assisted liquid–liquid extraction coupled to high-performance liquid chromatography to determine three aromatic hydrocarbons in aqueous samples

In this study, a new device for semi-automated salt-assisted liquid–liquid extraction was designed and coupled with high-performance liquid chromatography (HPLC) to determine three aromatic hydrocarbons in aqueous samples. In order to evaluate the performance of the designed device, three aromatic hydrocarbons including 2-naphthol, naphthalene and anthracene were selected as model analytes. Sample solution, extraction solvent and salt solution using separate channels were transferred to a sample holder, respectively. These three components were mixed using a magnetic stirrer. After stirrer stopping, the aqueous and organic phases were separated and organic layer transferred to the injection loop of HPLC system. Optimization process was achieved using response surface methodology by Design-Expert software. A central composite design was used to optimize the main parameters including pH (A), stirrer time (B), organic solvent volume (C) and salt concentration (D). The limit of quantitation for 2-naphthol, naphthalene and anthracene was 15.0, 25.0 and 1.0 ng mL^?1, respectively. Under the optimum conditions, obtained recoveries for three analytes were in the range of 76.0–96.2% with relative standard deviation less than 8.2%. The salt-assisted liquid–liquid extraction method using the proposed device has been successfully used for the analysis of real samples containing studied analytes in various matrices.     

Bounded complexes of cotorsion sheaves

We provide a necessary and su?cient condition which ensure that every flat quasi-coherent sheaf has finite cotorsion dimension. Also, we will show that every locally noetherian scheme with a dualizing complex has this requirement.     

Density functional studies of influences of Ni triad metals and solvents on oxidative addition of MeI to [M(CH3)2(NH3)2] complexes and C-C reductive elimination from [M(CH3)3(NH3)2I] complexes

Three metal square planar complexes of the type [M(CH₃)₂(NH₃)₂] (M = Ni, Pd, Pt), with a systematic variation in the metals, are chosen to investigating their S_N2-type oxidative addition reactions with methyl iodide by using the B3LYP levels of theory. The oxidative addition was found to take place via a transition state with a nearly linear arrangement of the I-CH₃-M moiety. Solvation effects in these oxidative addition reactions were also investigated. Considering the nature of the metal centre and solvation effects, the following conclusions emerge: (i) addition of MeI is exothermic for all three metals, and Pt is predicted to react with a much lower barrier than either Pd or Ni. The results describe that the MeI addition would be expected to be more favourable with the complex bearing the third-row metal (platinum) as compared to the other triad metals, nickel or palladium, in which case a more strongly bound MeI adduct is formed with a lower activation barriers and the reaction being more exothermic; (ii) the reaction is very difficult to occur in low polar solvents, such as benzene, due to the high barrier which is induced by dissociation of iodide anion from methyl group, but the reaction easily occurs in polar solvents, such as acetonitrile; this is attributed to the ability of polar solvents to solvate and therefore stabilize the related polar intermediate ion pair. Ethane reductive elimination from the M(VI) complexes fac-[M(CH₃)₃(NH₃)₂I] were also studied, indicating that the Ni(IV) and Pd(IV) complexes are very prone to undergo the reductive elimination while the Pt(IV) analogous is less reactive towards the reductive elimination. The results indicate that in contrast to the Me-Me reductive elimination, the S_N2 oxidative addition reaction of MeI to M(II) is much less sensitive to the nature of the metal centre, suggesting that the nucleophilicity of M(II) in [M(CH₃)₂(NH₃)₂] does not change significantly as one moves from M = Ni to Pt.     

Competition of methyltrioxorhenium (MTO) with osmium tetroxide (OsO4) for pyridines binding: Ligand binding assay

Competition of methyltrioxorhenium (MTO) with osmium tetroxide (OsO₄) toward L = pyridine and its derivatives, based on the equilibrium constant for the reaction OsO₄·L + MTO = MTO·L + OsO₄, has been measured. A successful correlation of log K_eq with the Hammett σ constants of the substituents on the ligands was realized. A negative reaction constant, obtained for the reactions, shows that a more positive charge expands on the pyridine nitrogen in the complex MTO·L as compared with the complex OsO₄·L. So, the rhenium center acts as a better electron acceptor than osmium center. The thermodynamic parameters have been obtained and an excellent linear relationship was observed between the enthalpy and entropy of the reactions.     

Ionic liquid mediated sol-gel sorbents for hollow fiber solid-phase microextraction of pesticide residues in water and hair samples

An ionic liquid mediated sol-gel sorbents for hollow fiber solid-phase microextraction (HF-SPME) was developed for extraction of the pesticides: diazinon, fenitrothion, malathion, fenvalerate, phosalone and tridemorph from human hair and water samples. The analytes were subsequently analyzed with high performance liquid chromatography and diode array detection (HPLC-DAD). Preliminary experiments were carried out in order to study experimental conditions for pesticides' extraction from spiked hair and water samples with HF-SPME using hollow fiber-supported ionic liquid mediated sol-gel sorbent. The sol-gel nanocomposites were reinforced with nanoparticles such as carboxylic functionalized multi-walled carbon nanotubes (COOH-MWCNTs), amino functionalized multi-walled carbon nanotubes (NH(2)-MWCNTs), nano SiO(2), nano TiO(2) and nano MgO comparatively to promote extraction efficiency. In this device, the innovative solid sorbents were developed by the sol-gel method via the reaction of tetraethylorthosilicate (TEOS) with 2-amino-2-hydroxymethyl-propane-1,3-diol (TRIS). In the basic condition (pH 10-11), the gel growth process in the presence of ionic liquid and nanoparticles was initiated. Then, the sol was injected into a polypropylene hollow fiber segment for in situ gelation process. Parameters affecting the efficiency of HF-SPME were thoroughly investigated. Linearity was observed over a range of 0.01-25,000 ng/mL with detection limits between 0.004 and 0.095 ng/mL for the pesticides in the aqueous matrices and 0.003-0.080 ng/mL in the hair matrices. The relative recoveries in the real samples ranged from 82.0% to 94.0% for the pesticides store seller's hair and the work researchers' hair. Results are showing the great possibilities of HF-SPME-HPLC-PDA for analysis of pesticides in biological and environmental samples.     

Application of Gaussian quadrature method to characterize heavy ends of hydrocarbon fluids for modeling wax precipitation

The hydrocarbon plus fractions that comprise a significant portion of naturally occurring hydrocarbon fluids create major problems when determining the thermodynamic properties and the volumetric behavior of these fluids by equations of state. These problems arise due to the difficulty of properly characterizing the plus fractions (heavy ends). Proper characterization of the heavier components is important when cubic equations of state and/or solid formation thermodynamic models are used to describe complex phase behavior of reservoir fluids. The effect of heavy fractions characterization on thermodynamic modeling of wax precipitation has been investigated using different models including Won, Pan and proposed models. In order to characterize the plus fraction (heavier part) as a series of pseudocomponents, a probability model that expresses the mole fraction as a continuous function of the molecular weight has been used. The study has been conducted using several mixtures. Two different SCN (single carbon number), C₇₊${\text{C}}_{7^{+}}$ and C₁₀₊${\text{C}}_{{10}^{+}}$ were chosen. The Chosen SCN were distributed to multi-components of five, six, and/or ten using continuous function and Gaussian quadrature method. The results showed that the fractioning is required to be able to predict wax precipitation. Distribution of C₁₀₊${\text{C}}_{{10}^{+}}$ using a proper distribution function has shown improvement in predictions of WAT and the amount of wax deposited in comparison with the characterization of C₇₊${\text{C}}_{7^{+}}$ using semi-continuous approach. In predicting of WAT and the amount of wax build up the developed model showed superiority over the others.     

Generalized gradients and characterization of epi-Lipschitz sets in Riemannian manifolds

In this paper, a notion of generalized gradient on Riemannian manifolds is considered and a subdifferential calculus related to this subdifferential is presented. A characterization of the tangent cone to a nonempty subset S of a Riemannian manifold M at a point x is obtained. Then, these results are applied to characterize epi-Lipschitz subsets of complete Riemannian manifolds.     

Molecular tectonics: design of enantiomerically pure helical tubular crystals with controlled channel size and orientation

The combination of four enantiomerically pure organic tectons composed of a rigid chiral backbone bearing two terminal pyridyl coordinating sites with ZnSiF(6) behaving as an infinite pillar leads to the formation of tubular 2-D enantiomerically pure helical channels with controlled size and orientation.