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To enhance the ecological properties of polyvinyl chloride (PVC) products, the fabrication of PVC-based composites using biofillers with acceptable performance characteristics could be considered. In this work, plant-filled PVC-based composite materials were fabricated and their optical, structural, thermal, and mechanical properties, depending on the nature of the filler, were studied. Spruce flour, birch flour, and rice husk were used as fillers. Optical measurements showed the selected technological parameters, allowing films with a uniform distribution of dispersed plant filler in the polymer matrix to be obtained. Using the plant fillers in PVC films leads to a reduction in strength characteristics; for instance, the tensile strength changed from 18.0 MPa (for pure PVC film) to ~7 MPa (for composites with 20 wt.% of fillers), and to ~5–6.2 MPa (for composites with 40 wt.% of fillers). Thermal investigations showed that the samples with plant fillers could be used at low temperatures without changing their operating characteristics. Thus, plant-filled PVC-based composite materials have a wide operating temperature range, from—65 °C to 150 °C. TGA analysis has demonstrated that the rice husk affected the thermal stability of the composites by increasing their thermal decomposition resistance. The ability to absorb water was observed during the investigation of water absorption of the samples. And the highest degree of water absorption (up to 160 mg/g) was detected for the sample with 40 wt.% of rice husk. In general, plant-filled polymer composites based on PVC can be used on an equal basis with unfilled PVC plastic compounds for some applications such as in construction (for example, for design tasks). [ABSTRACT FROM AUTHOR]

In this work, the overall activation energy of the combustion of lean hydrogen–methane–air mixtures (equivalence ratio φ = 0.7−1.0 and hydrogen fraction in methane α = 0 , 2, 4) is experimentally determined using thin-filament pyrometry of flames stabilised on a flat porous burner under normal conditions ( p = 1 bar, T = 20 °C). The experimental data are compared with numerical calculations within the detailed reaction mechanism GRI3.0 and both approaches confirm the linear correlation between mass flow rate and inverse flame temperature predicted in the theory. An analysis of the numerical and experimental data shows that, in the limit of lean hydrogen–methane–air mixtures, the activation energy approaches a constant value, which is not sensitive to the addition of hydrogen to methane. The mass flow rate for a freely propagating flame and, thus, the laminar burning velocity, are measured for mixtures with different hydrogen contents. This mass flow rate, scaled over the characteristic temperature dependence of the laminar burning velocity for a one-step reaction mechanism, is found and it can also be used in order to estimate the parameters of the overall reaction mechanisms. Such reaction mechanisms will find implementation in the numerical simulation of practical combustion devices with complex flows and geometries. [ABSTRACT FROM AUTHOR]

In this work, the determination of the apparent activation energy of a global chemical reaction mechanism of the methane–air flames is revisited. The one-step formulation allows to derive the theoretical background for the method to measure the activation energy within the burner stabilised flame setup. The validity of this approach is demonstrated by using the numerical simulations with the detailed reaction model and direct thin filament pyrometry measurements of the temperature distribution in flame. The combination of numerical and experimental approaches allows us to find the activation energy for various mixture compositions. The prediction of numerical simulations and measured values of the activation energy is found to be in good agreement with each other and the data known from the literature. It is demonstrated that two critical phenomena need to be taken into account to obtain a reliable estimate of the activation energy: the flame blow-off and the onset of the diffusive-thermal instabilities. The effect of these critical events on the accuracy of the measurements is discussed as well as prospects of further investigation. [ABSTRACT FROM AUTHOR]

Abstract: Gas sensitive layers with a fractal structure based on tin oxide were prepared by the sol–gel-method. Investigations of the film structure were carried out by atomic force microscopy. The basic evolution steps of this fractal system were found to be diffusion-limited aggregation, cluster–cluster aggregation, formation of percolating transition and netting nanostructures. Gas-sensitivity measurements of synthesized samples were taken. The emergence of a new relaxation in the presence of reducing gases was found in the Cole–Cole plots. Sensor nanostructures were investigated by impedance spectroscopy in different gas environments and gas reagent detection temperatures. AC measurements made it possible to develop selective gas sensors and multisensor systems. [Copyright &y& Elsevier]