Optimized formulation of an oxidative curing system for liquid polysulfide sealants used in fuel tanks by D‐optimal design method

In this work, the effective parameters in liquid polysulfide curing system were optimized by D ‐optimal design method. Five main components in the formulation, carbon black, vulcanizing agents (MnO₂, Na₂Cr₂O₇, and PbO₂), CaCO₃, fumed silica, and chlorinated paraffin, were selected. Mechanical and chemical properties of the samples were investigated. The results showed that tensile strength, hardness, viscosity, and optimum cure time (t₉₀) presented a suitable coordination with reduced quadratic model. For elongation at break and swelling tests, reduced two‐factor interaction (2FI), and for peel strength, a linear model showed the best correlation. To achieve the desirable properties for liquid polysulfide sealants used in fuel tanks, an optimized amount of the above components in the formulation were used. Finally, MnO₂ curing system, compared with Na₂Cr₂O₇ and PbO₂, was selected as the best choice. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Experimental investigation on mechanical properties of extruded foamed PVC‐wood composites reinforced with continuous glass fibers

In this study, mechanical performances of extruded foamed and unfoamed PVC‐wood composites, reinforced with continuous glass fibers, were investigated. A specially designed die was used to incorporate the continuous glass rovings into the extruded rectangular shaped profiles. The experimental variables were the number of continuous glass rovings (0–2‐4) and the presence or absence of the chemical foaming agent. Three point bending tests as well as density measurements were conducted to evaluate the mechanical properties and density reduction upon foaming. The results showed that the flexural strength of the reinforced profiles was significantly increased, as 58% increase in flexural strength was noticed for wood plastic composites (WPCs) reinforced with four glass rovings. The highest density reduction (14%) was observed upon foaming for profiles reinforced with four glass rovings, while resulting in strength deterioration. Moreover, results revealed the remarkable effect of reinforcement on preserving mechanical performance of the foamed samples, as 88% increase in flexural strength of the foamed samples reinforced with four glass rovings was observed compared with the unreinforced foamed ones. For the foamed WPCs reinforced with even two glass rovings, the higher specific strength values were also noticed compared to the unreinforced and unfoamed samples. POLYM. COMPOS., 37:1674–1680, 2016. © 2014 Society of Plastics Engineers     

Numerical modeling of heat transfer and fluid flow in hybrid laser–TIG welding of aluminum alloy AA6082

This paper describes a three-dimensional numerical model based on finite volume method to simulate heat transfer and fluid flow in laser–tungsten inert gas (TIG) hybrid welding process. To simplify the model and reduce the calculation time, keyhole dynamics are not considered; instead, a new modified volumetric heat source model is presented for the laser source to take into account the effect of the keyhole on the heat transfer into the workpiece. Due to the presence of arc current, an appropriate electromagnetic model based on the Maxwell equations are also solved to calculate electromagnetic forces in the weld pool. The results of computer simulation, including temperature, current density, electromagnetic, and melted material velocity field, are presented here. Furthermore, several dimensionless numbers are employed to recognize the importance of fluid flow driving forces in the weld pool. It is deduced that the fluid flow has an important effect on the weld pool shape. It is also founded that among the driving forces, Marangoni force is dominant fluid force in the weld pool. Besides, calculated results of hybrid welding process are compared with those of TIG and laser welding processes. The weld pool depth is relatively the same, but the width of the weld pool is highly larger in hybrid welding than lone laser welding. Eventually, the presented model is validated by comparison between calculated and experimental weld pool shape. It is founded that there is a good agreement as the capability of this model can be proved.     

Magneto Optical Properties of FeB<Subscript>x</Subscript>Fe<Subscript>2−x</Subscript>O<Subscript>4</Subscript> Nanoparticles

In this study, FeB_xFe_2?xO₄ nanoparticles (NPs) were synthesized by the polyol method. The M–H hysteresis curves exhibit superparamagnetic characteristics that are both coercivity and remanent magnetization values are negligible. The particle size dependent Langevin function was applied to calculate the magnetic particle dimensions around 9 nm. The measured magnetic moments of NPs are in range of (1.52–2.2) µ_B and almost half or less with respect to 4 µ_B of bulk Fe ferrite. Magnetic anisotropy was specified as uniaxial and calculated effective anisotropy constants (K _eff ) are between 43.3 × 10⁴ and 19.4 × 10⁴ emu/g. The UV–Vis diffuse reflectance spectroscopy and Kubelka–Munk theory were used to determine the optical properties. The estimated optical band gap values (2.15–2.48 eV) of FeB_xFe_2?xO₄ NPs are bigger with respect to reported values (1.88–2.12 eV) for Fe₃O₄ NPs in the literature. The bigger E _g values are mainly attributed to B concentration and partly to quantum confinement effect.     

Physical properties of normal grade biodiesel and winter grade biodiesel

In this study, optical and thermal properties of normal grade and winter grade palm oil biodiesel were investigated. Surface Plasmon Resonance and Photopyroelectric technique were used to evaluate the samples. The dispersion curve and thermal diffusivity were obtained. Consequently, the variation of refractive index, as a function of wavelength in normal grade biodiesel is faster than winter grade palm oil biodiesel, and the thermal diffusivity of winter grade biodiesel is higher than the thermal diffusivity of normal grade biodiesel. This is attributed to the higher palmitic acid C(16:0) content in normal grade than in winter grade palm oil biodiesel.     

Physical properties of palm‐based diacylglycerol and palm‐based oils in the preparation of shelf‐stable margarine

Ternary mixtures containing palm olein (POL), palm kernel oil (PKO) and palm oil‐based diacylglycerol (PO‐DAG) were designed using mixture design. The corresponding physical properties such as solid fat content (SFC) as well as deviation from SFC (ΔSFC) using nuclear magnetic resonance (NMR) and melting and crystallization properties using differential scanning calorimetry (DSC) were studied. Ternary phase behaviour was analysed using isosolid diagrams. The most intensive eutectic interaction among the three binary blends studied was observed along the binary line of PKO/PO‐DAG followed by POL/PKO and POL/PO‐DAG. The higher ΔSFC did not always lead to the more intensive eutectic behaviour among the blends. Addition of pure POL, 33.33 and 66.66% POL, and no POL to 50/50 mixture of PKO/PO‐DAG decreased heat of crystallization (ΔHc) as well as crystallization onset (T_O). However, as the same amounts of PO‐DAG and PKO were added to the 50/50 mixtures of POL/PKO and POL/PO‐DAG, respectively, blend containing the equi‐mixture of POL, PKO and PO‐DAG (33.33/33.33/33.33) was found to have the lowest ΔHc. This was also reflected in the corresponding eutectic effect observed at 20–25 and 5–10°C, respectively. Palm‐based DAG‐enriched shelf‐stable margarine consisting of POL/PKO/PO‐DAG (42.5/42.5/15 w/w) was optimally formulated through analysis of multiple isosolid diagrams and was found to have quite similar SFC profile with commercial shelf‐stable margarine. Practical applications: In this study, valuable information about complicated interactions among the palm oil‐based diacylglycerol (PO‐DAG) and palm‐based oils with different FA chain length was obtained in the ternary system. These informative data may be useful in future exploitation of solid fat‐based DAG in blend with natural fats for various DAG‐enriched plastic fat products. Furthermore, Design Expert software was found to be a valuable tool to optimize the new fat blend formulation using the minimum number of blend preparation. By using this tool, assessment of complicated behaviour among the blend components through construction of the corresponding phase diagrams which are critical for optimization purposes as well as fat product development, would also be possible.