Iranian Journal of Chemical Engineering (IJChE)

Abstract Plant fiber composites are currently experiencing strong development, particularly due to the growing interest in them in the automotive industry. These fibers are an excellent alternative to glass fibers from the environmental point of view due to their biodegradability and their much more neutral combustibility in terms of the release of harmful gases or solid residues. However, the incorporation of cellulosic materials into the thermoplastic matrix affects a large number of properties. Many factors, such as the nature and rate of the incorporated filler, can influence the properties of the composites. The present work involves studying the effect of the particle size of a natural fiber on the properties of a polymer matrix. The plant fibers used are DISS fibers ground into a powder with a particle size of less than 63µm. Different formulations based on HDPE/Diss were prepared with different amounts of the filler (10%, 20% and 30%). The HDPE/Diss composites were first processed using a calender, then molded into samples of various shapes with a thickness of 3 mm by compression at 190 °C. These were characterized by various techniques: physical tests, mechanical tests, rheological and morphological tests.

Abstract This research aims to study the mixing dynamics of granular materials in the Triaxe mixer and compare the effect of operating conditions on the quality of mixing. The discrete element method was used to simulate the mixer and track the motion of particles. The Johnson-Kendall-Robinson model was used for the simulation of the contact of cohesive particles. The results indicate that the most influential parameter on the mixing performance is the rotational speed since raising the rotational speed increases the transferred momentum to the grains. In the specific design of the mixer, the dead zones are reduced, so the fill-level does not have a considerable impact on the homogeneity. Also, the quality of mixing of large particles in this blender is better than the same for smaller particles. The mixer's performance for blending cohesive grains was similar to that for the non-cohesive particles. For both types of solids, the relative standard deviation reached approximately 35% after 70 s. Mixing performances of two sizes of the mixer were compared based on two criteria, the constant impeller speed and constant power per volume of the mixer. The results show that the case of the constant impeller speed can predict the mixing performance of the larger mixer more accurately.

Abstract Liners serve as both a barrier layer and an adhesive, bonding the insulation to the propellant. Plasticizer migration is a frequently observed phenomenon in solid propellants, often leading to detrimental effects on mechanical stability and performance.  Absorbent plasticizer liners have emerged as a next-generation solution, offering both anti-migration properties and adhesive capabilities. In this study, the anti-migration effects of three polyethers, including polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetrahydrofuran (PTHF) as liners in the presence of plasticizers 1,2,4-butanetriol trinitrate (BTTN),  trimethylolethane trinitrate (TMETN), and triethylene glycol dinitrate (TEGDN), were studied using NPT-molecular dynamics simulation (NPT-MD) with the Compass III force field. The binding energy, solubility parameter, and radial distribution function of polyethers containing 20% plasticizers were calculated.  The mixture of PEG and TEGDN exhibited the highest binding energy and compatibility. The solubility parameter reflects the strength of non-bonded intermolecular forces, indicating compatibility. The radial distribution function analysis showed strengthened van der Waals interactions, confirming compatibility. Molecular dynamics simulation results showed that polyethylene glycol is a suitable liner with anti-migration properties in propellants.

Abstract The goal of this study was to examine the morphology and characteristics of a blend of polylactic acid (PLA) with thermoplastic corn starch (TPS) and polyethylene glycol (PEG-400) using the extrusion process. The blends were evaluated through the tensile and impact strength tests, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. The experimental design method was selected to quantitatively analyze the influence of the content of TPS and concentration of the plasticizer on mechanical properties. Results from the tensile test showed that the addition of PEG-400 decreased tensile strength and elastic modulus, but increased elongation at break and impact strength, significantly. The blend with 20% TPS and 20 phr PEG-400 had the best overall performance in terms of tensile strength, elastic modulus, elongation at break, and impact strength. The SEM analysis indicated increased incompatibility and phase separation in samples with 40% TPS. Additionally, at high concentrations of PEG-400, the excessive plasticizer caused polymer saturation, resulting in unabsorbed plasticizer and phase separation. The findings suggest that the blend with 20% TPS and 20 phr PEG-400 could be suitable for use in eco-friendly applications.

Abstract Polymeric gels can be injected into reservoirs to regulate fluid dynamics and enhance oil recovery by creating physical barriers to redirect water flow. In this study, a polymer gel system was developed using sulfonated polyacrylamide combined with chromium acetate. Silica nanoparticles were synthesized via the sol-gel method, and their effects on the polymer gel system, including the gelation time and gel strength, at the concentrations of below 1% weight were evaluated through the bottle test. The performance of the polymer gel containing silica nanoparticles and the silica nanoparticle gel in formation waters was assessed. Furthermore, homogeneous microscopic models and heterogeneous two-layer microscopic models, which included regions with high and low permeability, were constructed to evaluate the functional effectiveness of the polymer gel and silica nanoparticle gel in porous media environments. Factors influencing oil recovery were examined in relation to the volume of injected pore water. The results indicated that silica nanoparticles enhanced the gel strength and increased its swelling capacity under saline conditions. Microscopic model testing in both homogeneous and heterogeneous configurations demonstrated that the silica nanoparticle gel provided better blockage in high-permeability regions and fractured zones, compared to the polymer-only gel. In the heterogeneous microscopic model, oil production rates were 55.60% for the polymer gel and 57.21% for the silica nanoparticle gel, while in the homogeneous model, these rates were 62.6% and 68.24%, respectively.

Abstract This study evaluates the effectiveness of the aluminum sulfate coagulation in treating the wastewater from thermal power plants to efficiently remove pollutants. Key operational parameters—the pH of the wastewater (5 to 9), dosage of coagulant (10 to 40 mg/L), and mixing time (10 to 30 minutes)—were systematically investigated for their impact on the removal of chemical oxygen demand (COD) and total dissolved solids (TDS). The coagulation mechanism involves the hydrolysis of aluminum sulfate, generating charged species that neutralize particle charges, followed by adsorption, bridging, and floc formation, which together promote the aggregation and sedimentation of pollutants. Utilizing the response surface methodology (RSM) with the Design Expert software, the process was optimized, revealing that a pH near 7.4, dosage of approximately 40 mg/L of the coagulant, and mixing time of around 22 minutes maximize the treatment efficiency. Under these conditions, the removal of COD and TDS reached 71.1% and 97.3% respectively, demonstrating the potential of this approach for the sustainable and cost-effective wastewater treatment in thermal power plant operations.