Effect of In Situ Polymerization of Styrene onto Natural Rubber on Adhesion Properties of Styrene-Natural Rubber (SNR) Adhesives

Styrene-based deproteinized natural rubber (SNR) latex was synthesized by in situ polymerization. Three pre-vulcanization systems [conventional-cured (CV), semi-efficient-cured (Semi-EV), and efficient-cured (EV)] were studied in terms of tensile and adhesion properties. Good tensile properties were observed for CV and EV SNR. The Semi-EV SNR showed the best adhesion properties based on the good anchorage performance in all substrate pairings (polystyrene–polystyrene, polystyrene–rubber, and rubber–rubber). The pH modification on SNR latex via KOH addition has beneficial effects of removing protein layers, resulting in more styrene grafting sites in the rubber molecules. Consequently, the tensile and adhesion properties of the SNR are improved as more styrene polymers are grafted onto the rubber matrix. Semi-EV SNR with pH 12 has superior adhesive performance; hence, it is suitable for use as a pressure-sensitive adhesive.     

New Statistical Concepts for Prediction Viscosity,Critical Temperature,and Critical Pressure of Homologous Hydrocarbon Series (C n H2n+2)

Abstract

A new model for prediction viscosity, critical temperature, and critical pressure for homologous hydrocarbon series C _n H_2n+2 as a function of carbon number only. The new model has a general formula: η or T _c or P = A ₁ C ^{A ₂} (2+2C) ^{A ₃} . This new model provides accurate and computationally reliable prediction for the corresponding properties (η, T _c , and P _c ) value.     

Impact of hydrogen concentrations on the impedance spectroscopic behavior of Pd-sensitized ZnO nanorods

ZnO nanorods were synthesized using a low-cost sol-gel spin coating technique. The synthesized nanorods were consisted of hexagonal phase having c-axis orientation. SEM images reflected perpendicular ZnO nanorods forming bridging network in some areas. The impact of different hydrogen concentrations on the Pd-sensitized ZnO nanorods was investigated using an impedance spectroscopy (IS). The grain boundary resistance (R_gb) significantly contributed to the sensing properties of hydrogen gas. The boundary resistance was decreased from 11.95 to 3.765 kΩ when the hydrogen concentration was increased from 40 to 360 ppm. IS gain curve showed a gain of 6.5 for 360 ppm of hydrogen at room temperature. Nyquist plot showed reduction in real part of impedance at low frequencies on exposure to different concentrations of hydrogen. Circuit equivalency was investigated by placing capacitors and resistors to identify the conduction mechanism according to complex impedance Nyquist plot. Variations in nanorod resistance and capacitance in response to the introduction of various concentrations of hydrogen gas were obtained from the alternating current impedance spectra.     

Design,fabrication and testing of a PMMA-based passive single-cell and a multi-cell stack micro-DMFC

A passive, air-breathing polymethyl methacrylate (PMMA) based single-cell and a multi-cell stack micro-direct methanol fuel cell (DMFC) with 1.0 cm² active area with a novel cathode plate structure and assembly layer are designed, fabricated and tested. The fuel cell is completely passive with no auxiliary device such as pump or fan. Oxygen is taken from the surrounding air, and the methanol solution is stored in a built-in reservoir. The performance of the single cell is tested with different methanol concentrations ranging from 1.0 M to 5.0 M, and the optimum performance is achieved by using methanol at a concentration of 4.0 M. A stack with 6 cells is fabricated and tested with the optimum methanol concentration of 4.0 M, and power levels produced by different catalyst loadings on the anode are compared. Besides, this study also considers the cost analysis of micro-DMFC. The combination of a catalyst loading of 3.0 mg cm⁻² Pt/Ru on the anode and 2.0 mg cm⁻² Pt on the cathode yield the highest power of 12.05 mW at 1.08 V and 11.2 mA. The total cost for the micro-DMFC in this study is only about USD 2 mW⁻¹.     

The composition of the extractives from unaffected and heartrot affected heartwood of Acacia mangium Willd

A. mangium has been studied by a successive extraction of the wood with a series of solvents with increasing polarity, followed by GC, GC/MS and DC studies of the fractions obtained. The study of the extractives of sound and affected wood with respect to yield and composition cannot explain the influence of the heartrot fungi on wood components in detail. Differences mainly have been found in the more polar fractions (acetone/water and ethanol/water, respectively). The content of lipophilic extractive constituents is with about 0.6–0.7% rather low and does not differ between sound and affected heartwood. The composition of the lipophilic extractives is not very different either.

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A. mangium wurde untersucht, wobei sukzessiv mit einer Reihe von L?sungsmitteln ansteigender Polarit?t extrahiert und die einzelnen Fraktionen mit Hilfe von GC, GC/MS und DC untersucht wurden. Die Untersuchung der Extrakte aus gesundem und befallenem Holz zeigte, da? Extraktausbeuten und Zusammensetzung den Einflu? des Pilzbefalls auf die Holzkomponenten nicht detailliert beschreiben K?nnen. Unterschied in Ausbeute und Zusammensetzung der Extrakte wurden haupts?chlich in den polaren Extraktfraktionen (Aceton/Wasser- und Ethanol/Wasser-Extrakte) gefunden. Der Gehalt an lipophilen Extraktbestandteilen ist mit etwa 0.6–0.7% eher niedrig, gesundes und befallenes Holz unterscheiden sich praktisch nicht. Auch die Zusammensetzung der lipophilen Extrakte ist kaum verschieden zwischen gesundem und befallenem Holz.

     

Nature-inspired optimization algorithms for community detection in complex networks: a review and future trends

Telecommunication Systems - Over the past couple of decades, the research area of network community detection has seen substantial growth in popularity, leading to a wide range of researches in the...     

ZnO quantum dot based thin films as promising electron transport layer: Influence of surface-to-volume ratio on the photoelectric properties

ZnO quantum dots (QDs) with average particle size of 4.4 nm were prepared using a low temperature processing solvothermal route. ZnO QD based thin films were then prepared from the ZnO QD based solution using spin coating technique and annealed at 250, 350 and 450 °C. The average grain size and energy band gap of ZnO were respectively increased and decreased from 5.5 to 22.9 nm and 3.37 to 3.27 eV upon increasing the annealing temperature up to 450 °C. The photoluminescence analysis showed that the as-coated ZnO film and ZnO film annealed at 250 °C have high density of oxygen vacancies; these defects were reduced upon increasing the temperature to 350 and 450 °C. The photoelectric properties of the films were strongly affected by the grain size and the defects present in the films. The photo-to-dark current ratio (PDCR) was decreased from 3723 to 371%, whereas the responsivity was increased from 1.25 to 218 mA/W with the increase of temperature to 450 °C. As-coated and 250 °C-annealed films exhibited better photoresponse than others in terms of PDCR, rise time and fall time due to their larger surface-to-volume ratio, making them promising candidate as electron transport layer in perovskite solar cells.     

Prediction Enthalpy of Hydrocarbon Vapor at Atmospheric Pressure

A generalized enthalpy-temperature correlation for light hydrocarbon vapor has been developed to represent the data for a wide range of temperatures 460-1080°F. Detailed analysis shows that the proposed correlation fits the experimental measurements of vapor enthalpy with the corresponding calculated values with an overall absolute error of 1.8% for 131 data points.     

Electrical determination of bandgap narrowing in bipolartransistors with epitaxial Si, epitaxial Si1-xGex,and ion implanted bases

The apparent bandgap narrowing in bipolar transistors with epitaxial Si, epitaxial SiGe and ion implanted bases is measured from the temperature dependence of the collector current density J_c(T). A graph of InJ_c(T)/J_o(T) as a function of reciprocal temperature is plotted, and the apparent bandgap narrowing obtained from the slope. For epitaxial base transistors, in which the boron base profiles are abrupt, a linear J_c(T)/J _o(T) characteristic is obtained, which allows the unambiguous determination of the apparent bandgap narrowing. The measured values for epitaxial Si bases are in good agreement with the theoretical model of Klaassen over a range of base doping concentrations. For Si_0.88 Ge_0.12 and Si_0.87Ge_0.13 epitaxial base heterojunction bipolar transistors (HBT's), values of bandgap narrowing of 119 and 121 meV are obtained due to the presence of the Ge, which can be compared with theoretical values of 111 and 118 meV. For the implanted base transistor, the J_c(T)/J_o(T) characteristic is not linear, and its slope is larger at high temperatures than at low. This behaviour is explained by the presence of a tail on the ion implanted profile, which dominates the Gummel number of the transistor at low temperatures