A comparative study to assess structure–properties relationships in (acrylonitrile butadiene rubber)‐based composites: Recycled microfillers versus nanofillers

This paper reports on the reinforcing effects of different types of fillers, namely, nanoclay (NC), micron size calcium carbonate (MCC), and micron size recycled powder coating waste (MPCW), on the ultimate properties of acrylonitrile butadiene rubber (NBR) compounds. The microcomposites and nanocomposites were characterized by X‐ray diffraction and scanning electron microscopy, implying enlargement of d‐spacing of NC or intercalation of NBR chains and formation of exfoliated structure, while some agglomerates of MCC were detected. Curing characteristics of the studied composites showed that incorporation of the fillers into the NBR, in particular the NC, causes an increase in the torque, indicating a higher degree of crosslinking. Furthermore, different from micron size MPCW and MCC, the NC accelerated the vulcanization reaction. It was also found that the use of NC and MPCW results in a remarkable increase in the mechanical and rheological properties compared with pure NBR. All in all, variations in the aforementioned criteria were attributable to the extent of matrix/filler interaction reflected by scanning electron micrographs. The correlation established between the microstructure and characteristics of the prepared NBR composites can shed some light on how to develop composites with enhanced properties by incorporating waste materials into the polymers. J. VINYL ADDIT. TECHNOL., 23:13–20, 2017. © 2015 Society of Plastics Engineers     

Numerical modeling of an umbrella arch as a pre-support system in difficult geological conditions: a case study

In order to prevent the collapse of ceilings and walls of large tunnels, especially in difficult geological conditions, either a sequential excavation method (SEM) or ground reinforcing method, or a combination of both, can be utilized. The first part of the adit tunnel in northwestern Iran is being drilled in alluvium material with very weak geotechnical parameters. Despite applying an SEM in constructing this tunnel, analyzing the numerical modeling done using FLAC3D, as well as observations during drilling, indicate tunnel instability. To increase operational safety and to prevent collapse, a pre-support system was designed and implemented. The results of the numerical modeling accompanied by monitoring during operation, as well as the results of instrumentation, indicate the efficacy of this method for preventing collapse in alluvium material along the tunnel route. Modeling the behavior of the umbrella arch shows that the location of the maximum compressive force will change with a change in the tunnel arc location. Moreover, displacement, force and moment exerted on the pipes will change during drilling steps according to a certain pattern.     

A kinetic model for pyrolysis of petroleum residue under nonisothermal conditions

Kinetic study on pyrolysis of petroleum residue was carried out by an accurate Arrhenius type equation at heating rate of 0.5–30.0°C/min under nonisothermal conditions. The influence of some critical parameters including temperature, heating rate and activation energy on mass conversion was evaluated. The apparent activation energies for during the pyrolysis process were in the range of 198–361 kJ/mol at various mass conversions of 5–94%. The reaction temperature was introduced as the most important parameter for the improvement of mass conversion, compared to that of other parameters. The pyrolysis of petroleum residue was occurred in a broad temperature range, from 150–650°C, yielding 33 wt% unpyrolyzed residue. It also was found that an increase in heating rate has a minor impact in the process. Model predictions were compared with experimental data, which showed fully good agreement.     

Effect of physical aging on the impact retention and heat distortion temperature of vinyl products

Physical properties of polymers change with time. Exposure of amorphous polymers to high temperature will reduce their free volume, which in turn increases their heat distortion temperature and decreases their impact strength. Heat distortion additives, such as poly(α-methylstyrene-styrene-acrylonitrile) (AMSAN), enhance the glass transition temperature of PVC and help in the impact retention of the polymer by slowing down the aging process. In this paper, physical aging of PVC is explored, effect of annealing time and temperature on the impact strength and HDT is reported, and conclusions regarding the retention of impact resistance upon aging are drawn.     

Assessment of immobilized cell reactor and microbial fuel cell for simultaneous cheese whey treatment and lactic acid/electricity production

Two biological methods for treatment of cheese whey and concentrated cheese whey were investigated in this research. As the first method, fermentation of cheese whey for production of lactic acid, in an immobilized cell reactor (ICR) was successfully carried out. The immobilisation of Lactobacillus bulgaricus was performed by the enriched cells cultured media harvested at exponential growth phase. Furthermore, the FTIR analysis has been done to prove the production of lactic acid. The COD removal during the continuous process for both whey and concentrated whey was above 70% which showed the capability of reaction for wastewater treatment. The cells were immobilised by sodium alginate as a perfect polymer in this regard. The maximum produced lactic acid from whey was 10.7 g l^?1 at 0.125 h^?1 and 19.5 g l^?1 from concentrated whey at 0.063 h^?1. Finally it can be concluded that the process is efficient for lactic acid production and COD removal simultaneously. As the second studied method, whey and concentrated cheese whey were used as the sources of carbon in a microbial fuel cell. The power densities of 188.8 and 288.12 mW m^?2 were recorded for whey-fed and concentrated whey-fed MFCs while the COD removal were 95% and 86% respectively. Biological wastewater treatment can be a very efficient alternative for traditional wastewater treatment which selecting any and or integrating of them depends on specific applications needed to be achieved.     

Fuzzy modeling of the forced convection heat transfer from a V‐shaped plate exposed to an air slot jet

This paper focuses on the application of fuzzy logic (FL) to predict the forced convection heat transfer from V‐shaped plate internal surfaces exposed to an air impingement slot jet. The aim of the present paper is to consider the effects of the angle of a V‐shaped plate (Φ), slot‐to‐plate spacing ratio (Z/W), and Reynolds number (Re) variation on average heat transfer from the V‐shaped plate internal surfaces. The data used for developing the FL structure was obtained experimentally by a Mach‐Zehnder interferometer. The proposed FL was developed using MATLAB functions. It was observed that the average Nusselt number will be decreased with an increase in jet spacing and be increased with an increase in Reynolds number and angle of V‐shaped plate. Moreover, it is also shown that fuzzy logic is a powerful technique to use for predicting heat transfer due to its low error rate. The average error of the fuzzy predictions compared with experimental data was found to be 0.33% for this study. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21009     

Irreducible compositions of polynomials over finite fields of even characteristic

This paper presents some results with the constructive theory of synthesis of irreducible polynomials over a Galois field with even characteristic. We prove a theorem that plays an important role for constructing irreducible polynomials. By this theorem two recurrent methods for constructing families of irreducible polynomials of degree $n2^{k}~(k=1,2,\ldots )$ over $\mathbb F _{2^{s}}$ are proposed. It is shown that in this special case, the sequences of irreducible polynomials are N-polynomial of degree $2^{k}$ .     

Estimation of Thermal Stresses in Hot-Rolled Steel Coils During Natural Air Cooling

Hot-rolled steel coils are stored upon manufacturing to cool to about 50°C. High temperatures of coiling cause thermal stresses during the cooling stage that result in spot welding between strip layers of coil. Under these conditions, surface defects or strip ruptures may occur during uncoiling. This paper will initially introduce the heat transfer model in the coil based on stress-dependent thermal conductivity in the radial direction of the coil. The two approaches of “solid body” and “thin-walled, concentric cylinders” for thermal stress analysis will then be used to compute the thermal compressive stresses in the coil. Comparison of the results obtained from these two approaches in the mathematical model reveals that the solid body approach overestimates the thermal stresses when compared to the thin-walled concentric cylinders approach, the inequality rising with reduced strip thickness. This difference, however, is found to have no considerable impact on predicting coil temperature.     

Copper-poly (2-aminodiphenylamine) composite as catalyst for electrocatalytic oxidation of formaldehyde in alkaline media

The present work describes the electrocatalytic oxidation of formaldehyde on a copper-polymer modified electrode. The deposition of polymeric film on the surface of carbon paste electrode (CPE) was carried out using consecutive cyclic voltammetry in an aqueous solution of 2-aminodiphenylamine (2ADPA). The transition metal of copper is incorporated into the polymer by electrodeposition of Cu(??) from CuCl₂ acidic solution using potentiostatic technique. Characterization of different modified electrodes was studied using SEM technique and electron probe microanalyzer (EPMA). Cyclic voltammetry experiment of copper-poly(2-aminodiphenylamine) modified carbon paste electrode (Cu/P(2ADPA)/MCPE) in alkaline solution exhibited a number of well-defined anodic and cathodic peaks that are attributed to the Cu/Cu(I), Cu/Cu(II), Cu(I)/Cu(II) and Cu(II)/Cu(III) redox couples. The electrocatalytic oxidation of formaldehyde at the surface of Cu/P(2ADPA)/MCPE was studied by cyclic voltammetry and chronoamperometry methods. This new modified electrode found to be highly active and stable for electrooxidation of the formaldehyde so that the electrocatalytic current density of 25.56 mA cm⁻² was obtained at the potential of 0.63 V. The effects of various parameters such as the copper loading, scan rate and formaldehyde concentration on the electrocatalytic oxidation of formaldehyde were also investigated. Finally, using a chronoamperometric method, the catalytic rate constant (k) for oxidation of formaldehyde was found to be 7.16 × 10⁶ cm³ mol⁻¹ s⁻¹.