A comparative study on curing characteristics and thermomechanical properties of elastomeric nanocomposites: The effects of eggshell and calcium carbonate nanofillers

After‐hatching eggshell (AHES) nanobiofiller and nanocalcium carbonate (nano‐CA) were separately added to various elastomers, such as acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), and natural rubber (NR), in various amounts of 5, 10, and 15 phr. The effect of particle size and dispersion of such nanofillers on thermomechanical properties and curing characteristics were then investigated. The ultimate tensile properties of SBR and NR nanocomposites were improved to some extent when 5 phr of AHES nanofiller was added to the rubber compound compared to CA. In the case of NBR nanocompounds, however, the mechanical properties were seemingly comparable, irrespective of the type of nanofiller. This contradictive behavior could be attributed to the alteration of crosslink density due to particular filler–matrix interaction while using mineral and natural fillers. The results of the rheometric study revealed that using AHES rather than CA slightly increases the scorch time of all types of prepared nanocomposites, whereas a significant drop in the optimum curing time was seen for NBR nanocomposites containing AHES biofiller. Moreover, thermogravimetric analysis showed similar thermal stability for SBR nanocomposites containing AHES and CA fillers. Finer particle size of CA and higher porosity of AHES at high and low loading levels were respectively the main reasons for improvement of ultimate properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermogravimetric Analysis of a Cellulosic Fabric Incorporated by Synthetic Ammonium Magnesium Phosphate as a Flame-Retardant

We have investigated the effect of synthetic struvite (MgNH₄PO₄·6H₂o) on the flammability of a cellulosic fabric. It was synthesized by means of the multiple-bath method and deposited onto a cotton fabric. Its uniformity was ensured by means of squeeze rolls, obtaining the optimum effective add-on value of ammonium magnesium phosphate to impart flame retardancy to cotton fabric in the range of around 12 g anhydrous salt per 100 g fabric. A thermogravimetric analysis of pure cotton, treated cotton, and the salt was accomplished, and their thermograms were compared and commented upon. The results obtained fortified the chemical theory expressing the promotion of the formation of solid char rather than the formation of volatile pyrolysis products, during the fulfillment of thermal decomposition of the cellulosic substrate.     

Influence of metallic substrate surface engineering on peel resistance of adhesively bonded polymer film

The peel resistance of adhesively bonded polymer films to a stainless steel sheet substrate (SSSS) with different engineered surface characteristics was examined in two different loading directions and for two different peel speeds. The SSSS was laminated with two thin polymeric adherends using two different pressure-sensitive adhesives. The SSSS surface was altered by grinding and knurling techniques before lamination and the effects of surface alterations on peel resistance were compared with peel resistance of the adherend from as-received SSSS with a bright annealed surface condition. For ground surface, an increase in adherend peel resistance was observed and the increase was attributed to increase in contact area between the adhesive and SSSS surface. For knurled surfaces which involved deeper and less frequent grooves, however, a decrease in peel resistance was observed. This was attributed to a more complex stress state at the peel front in the SSSS groove region during peeling. An increase in peel speed enhanced the peel resistance from both ground and knurled surfaces.     

Failure of silver nanowire transparent electrodes under current flow

Silver nanowire transparent electrodes have received much attention as a replacement for indium tin oxide, particularly in organic solar cells. In this paper, we show that when silver nanowire electrodes conduct current at levels encountered in organic solar cells, the electrodes can fail in as little as 2 days. Electrode failure is caused by Joule heating which causes the nanowires to breakup and thus create an electrical discontinuity in the nanowire film. More heat is created, and thus failure occurs sooner, in more resistive electrodes and at higher current densities. Suggestions to improve the stability of silver nanowire electrodes are given.     

Preparation of novel 2-(2-oxo-2H-chromen-4-yl)-3- arylthiazolidin-4-one derivatives using an efficient ionic liquid catalyst

An eco-friendly procedure for synthesis of 2-(2-oxo-2H-chromen-4-yl)-3-arylthiazolidin-4-one derivatives by three-component reaction of 2-oxo-2H-chromene-4-carbaldehydes, aromatic amines and thioglycolic acid, with tetramethylbutane-1,4-diammonium acetate as a low-cost ionic liquid catalyst under reflux condition is described. The use of an ionic liquid as a catalyst has the advantages of high yields, short reaction time and environmentally friendly reaction media.     

Electrocatalytic and simultaneous determination of isoproterenol, uric acid and folic acid at molybdenum (VI) complex-carbon nanotube paste electrode

This paper describes the development, electrochemical characterization and utilization of a novel modified molybdenum (VI) complex-carbon nanotube paste electrode for the electrocatalytic determination of isoproterenol (IP). The electrochemical profile of the proposed modified electrode was analyzed by cyclic voltammetry (CV) that showed a shift of the oxidation peak potential of IP at 175 mV to less positive value, compared with an unmodified carbon paste electrode. Differential pulse voltammetry (DPV) in 0.1 M phosphate buffer solution (PBS) at pH 7.0 was performed to determine IP in the range from 0.7 to 600.0 μM, with a detection limit of 35.0 nM. Then the modified electrode was used to determine IP in an excess of uric acid (UA) and folic acid (FA) by DPV. Finally, this method was used for the determination of IP in some real samples.     

Effect of Melt Processing on Crystallization Behavior and Rheology of Poly(3‐hydroxybutyrate) (PHB) and its Blends

Poly(3‐hydroxybutyrate) (PHB) is sensitive to high processing temperatures. This leads to a decrease in molar mass as well as a lower melt viscosity. The crystallization temperature shifts to lower values, and crystallization kinetics is slow. A mixture was developed in order to improve the manufacturing properties and the final product. The blends exhibit a slight reduction in molar mass because they have a lower melting point than pure PHB, and can be extruded at their melt temperature of 170 to 180°C. Then they immediately crystallize at 125 to 100°C. Differential scanning calorimetry (DSC) shows the effect of holding time in the melt on crystallization behavior. It has been shown that the crystallization time has to be longer in the case of PHB and shorter for the blends. Thermal degradation of PHB and its blends has been investigated using thermogravimetry analysis (TG). Derivative thermogravimetry coupled with TG (TG/DTG) curves show three decomposition stages for blends at 290, 340 and 445°C, respectively. Acetic acid, water, carbon dioxide and methane are produced by degradation at a higher temperature.     

Modeling industrial thickener using computational fluid dynamics (CFD), a case study: Tailing thickener in the Sarcheshmeh copper mine

Separation of particles from liquid in the large gravitational tanks is widely used in mining and industrial wastewater treatment process. Thickener is key unit in the operational processes of hydrometallurgy and is used to separate solid from liquid. In this study, population balance models were combined with computational fluid dynamics (CFD) for modeling the tailing thickener. Parameters such as feed flow rate, flocculant dosage, inlet solid percent and feedwell were investigated. CFD was used to simulate the industrial tailing thickener with settled bed of 120 m diameter which is located in the Sarcheshmeh copper mine. Important factor of drag force that defines the rake torque of rotating paddles on the bed was also determined. Two phases turbulence model of Eulerian/Eulerian in accordance with turbulence model of k-ε was used in the steady-state. Also population balance model consists of 15 groups of particle sizes with Luo and Lehr kernel was used for aggregation/breakage kernel. The simulation results showed good agreement with the operational data.     

Strain‐rate‐dependent mechanical properties of polypropylene separator for lithium‐ion batteries

The mechanical integrity of battery separators is critical for battery safety and durability. A comprehensive study of strain‐rate‐dependent tensile and puncture properties of a polypropylene lithium‐ion battery separator is presented here with a new model. Due to anisotropy of the polymeric membrane, tensile testing was conducted for different directions. Results showed that tensile strength and elastic modulus were increased 1000% and 500%, respectively, for different directions. It was also demonstrated that tensile strength changed 10 to 25% with strain rate (1.67 × 10^?4 to 1.67 × 10^?1 s^?1) for different directions. An equation was obtained for the first time for flow stress versus strain rate at varied tensile directions with respect to machine direction. Moreover, puncture testing was performed and it was shown that puncture strength was increased 140% with increasing strain rate from 0.25 to 250 mm min^?1. Two failure modes were also observed in puncture samples. Finally, Eyring's model was used to calculate activation enthalpy of the porous polypropylene separator. © 2020 Society of Chemical Industry     

Electrical and mechanical properties of BZT − xBCT lead-free piezoceramics

In this study, lead-free (1 − x)Ba(Zr_0.2Ti_0.8)O₃ − x(Ba_0.7Ca_0.3)TiO₃ compositions are synthesized via conventional solid oxide route, and the ceramics are fabricated with normal sintering in air. The effects of composition fluctuations on dielectric, piezoelectric, and mechanical properties are investigated. The phase structure and the microstructure are analyzed with X-ray diffraction and scanning electron microscopy. The best dielectric and piezoelectric properties of ε_r = 11 207 and d₃₃ = 330 pC/N were obtained for BZT−0.35BCT and BZT−0.5BCT ceramics, respectively. The mechanical behavior—in terms of Vickers hardness and compressive and flexural strengths—was investigated, and the best mechanical behavior was found in the vicinity of the phase transition boundary with x values between 0.5 and 0.6.