Colloid and Polymer Science最新文献

The exceptional heat transfer capabilities of hybrid base ferrofluids have attracted numerous researchers, prompting an increase in investigations into these working fluids. In various applications, hybrid base nanofluids have demonstrated superior heat transfer performance. However, further research is needed to expand their range of applications. To address this need, the current study aims to explore the flow of a hybrid base nanofluid (magnetite with ethylene glycol and water as the base fluid) on an exponential shrinking/stretching Riga plate with radiative heat flux. The Riga plate, an electromagnetic actuator, consists of a spanwise-aligned array of alternating electrodes attached to a flat surface and permanent magnets. This setup enables the examination of heat transfer with Hartmann number, thermal radiation, and nanoparticle volume fraction. The governing PDE systems are transformed into ODE systems using similarity transformations, and the developed model is solved numerically using the bvp4c technique in MATLAB software. A comprehensive convergence analysis and comparative investigation of numerical data are conducted to ensure the accuracy of the results. Finally, the effects of physical parameters on skin frictional force, Nusselt number, velocity field, and temperature field are investigated, and the results are presented graphically and discussed in detail. The numerical values for the skin frictional quantity variation along suction with different Hartmann quantity obtained. The critical values ({S}_{ci},i=1, 2), and (3) observed are (2.2396, 2.3795,) and (2.7714) corresponding to the values of (M) = (0, 0.02,) and (0.04), respectively. Research suggests that dual solutions are present within a specific spectrum of suction and stretching/shrinking parameters. Additionally, the stability analysis of these dual solutions indicates that the primary solution is stable.

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Porous melamine formaldehyde resin (PMF) was synthesized without using template in aqueous solution with a green preparation method. Conditions such as formaldehyde/melamine, concentration, curing temperature, and time on pore parameters of synthesized porous melamine formaldehyde resin were investigated. The chemical property and pore structure of porous melamine formaldehyde resin were characterized by infrared spectroscopy, SEM, and BET. The results showed that the samples synthesized in solvent water had a surface higher than 490 m²/g, pore diameter of about 12.0 nm, and pore volume of about 1.2 cm³/g. The surface area and pore structure of porous melamine formaldehyde resin could be adjusted by changing the prepolymer concentration. Due to the large pore diameter and volume, it also adsorbed a great amount of Congo Red (CR), indicating an excellent adsorbent for large molecules. This investigation reveals that the -NH₂ and pore structure have great effects on the adsorption capacity of Congo Red dye of the as-synthesized melamine formaldehyde resin samples.

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The porous melamine formaldehyde resin without using template was synthesized by a green preparation method. The pore structure of the melamine formaldehyde resin was formed by nanoparticles accumulation. The surface area and pore structure of porous melamine formaldehyde resin could be adjusted by changing the prepolymer concentration. The adsorption capability of the porous melamine formaldehyde resin for Congo Red was up 720 mg/g.

Thermoplastic polyester elastomer (TPEE) microcellular foam materials prepared using supercritical carbon dioxide (scCO₂) as a physical blowing agent suffer from poor dimensional stability, which significantly limits their applications across various fields. This study thoroughly investigates the prevalent issues of high shrinkage and low expansion ratio in the scCO₂ foaming process of TPEE. By introducing poly(lactic acid) (PLA), a rigid material with moderate compatibility, into TPEE through blend modification, we markedly improved the shrinkage behavior of foamed TPEE while enhancing its expansion ratio. The experiments successfully produced TPEE/PLA20 microcellular foams with a stable expansion ratio of 19 times. Compared to pure TPEE, the shrinkage rate decreased from 77.3 to 19.0%. Due to its moderate compatibility, PLA was uniformly dispersed within the TPEE matrix as a dispersed phase, which refined the cell structure through heterogeneous nucleation and reduced cell walls strain. Additionally, rigid PLA micro/nanoparticles acted as stress concentration points, promoting the formation of an open-cell structure by causing cell walls rupture, thereby accelerating gas diffusion. More importantly, high glass transition temperature (T_g) PLA nanoparticles are stretched and embedded in the cell walls during the foaming process, and the heterogeneous nucleation effect of PLA enhances the crystallinity of TPEE. These two factors together increase the rigidity of the cell walls. The synergistic effects of these factors enabled the TPEE/PLA microcellular foam materials to effectively resist shrinkage caused by the pressure differential between the inside and outside of the cells and molecular chain relaxation.

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In this study, a novel adsorbent—KOH-treated bentonite biochar composite (BRK) derived from natural bentonite and rice husk—was successfully synthesized to remove ammonium (NH₄⁺) from water. Adsorbent preparation involved pyrolysis at 400 °C followed by activation of biochar with KOH to produce BRK. Various techniques were applied to characterize the investigated adsorbent, including Fourier-transform infrared spectroscopy (FTIR), N₂ adsorption analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM) integrated with energy-dispersive X-ray (EDX) spectroscopy. Batch experiments were conducted for elucidating the factors influencing the adsorption process, including pH, contact time, temperature, initial ammonium concentration, and the presence of co-existing cations in the solution. The results showed that the pH of the solution strongly affected BRK’s adsorption capacity for NH₄⁺ ions. Co-existing cations (Na⁺, K⁺, Ca²⁺, and Mg²⁺) significantly reduced the removal efficiency of NH₄⁺ ions. The Langmuir adsorption capacity of BRK for NH₄⁺ followed the order: 22.51 mg/g (10 °C) > 20.57 mg/g (30 °C) > 16.22 mg/g (50 °C). The negative standard enthalpy change (∆H°) obtained in thermodynamic study suggested that the adsorption process of NH₄⁺ was exothermic. The kinetic experiments demonstrated that adsorption equilibrium was achieved after 30 min of contact. Ion exchange was found to be the main adsorption mechanism for removing NH₄⁺ by BRK. This study proved that BRK is a low-cost and sustainable adsorbent derived from natural bentonite and rice husk and is advantageous for removing NH₄⁺ from water.

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Hot work can make oil pipeline maintenance more efficient but is dangerous. Traditional chemical hydrogels can plug oil pipelines to ensure the safety of hot work, but they cannot be completely removed afterward. Herein, we prepared a gelatin-reinforced hydrogel with thermal reversibility, which can be easily removed by injecting hot water. The hydrogel was prepared by the hydrogen bonds of the copolymer of N-acryloyl glycinamide (NAGA) and acrylamide (AM) as well as the interaction of the gelatin interpenetrating network. It was found that the hydrogen bonding interaction between the NAGA motif is the main driving force for the formation of hydrogels. The strength of the hydrogel is increased by 10 times after adding gelatin equivalent to the polymer. The thixotropic recovery properties test indicated that the hydrogel posed tunable mechanical and self-recovery properties, which contributed to the excellent plugging ability and injectability of hydrogels. Besides, the hydrogels exhibit favorable thermo-reversible gel-sol transition behavior, driven by the reversible disruption of hydrogen bonding interactions in response to temperature changes. Hydrogel showed good flame retardancy with values of heat release rate (HRR) below 5 kW/m² during the test time of 200 s, which is beneficial to the safety in the construction of hot work. Our findings confirmed that the hydrogel demonstrated an effective plugging effect in the simulated pipeline, and the residual hydrogel could be easily removed by injecting hot water. Hydrogels with thermo-reversibility can meet the plugging requirements for oil pipelines during hot work, simplifying the operation process and enhancing work efficiency.

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The work studied the formation and structure of (bio)PEC in mixtures of dilute chitosan and gelatin solutions at different pH and ratios of polymers and their ionized groups of z. Using the turbidimetry method for the chitosan and gelatin mixtures, it was found that stable scattering particles of (bio)PEC are formed in the pH range from 5 to 6.4 and with a polymer ratio above 1:5 (z = 0.29). The electrostatic interaction in the (bio)PEC structures was confirmed by ATR-FTIR spectroscopy. It was shown that during the formation of (bio)PEC in mixtures with pH = 5.5, a strong shift of the corresponding absorption bands relative to the initial polymers is observed. Studying the complexation and structure of these particles using the dynamic light scattering method of mixtures at pH = 3, the associative-dissipative character of the polymers interaction with the formation of soluble and unstable (bio)PEC dispersions was determined. It was observed that in mixtures with a pH = 5.5, the interaction becomes associative, which is accompanied by the formation of a (bio)PEC coacervate microphase at polymer ratios from 1:10 to 1:30 (in the z range from 0.58 to 1.73, respectively). Analysis of the structural properties of the coacervate microphase of (bio)PEC using dynamic light scattering and optical microscopy methods showed that with an increase in the proportion of an oppositely charged component of z ≥ 1, the isotropy of the polyelectrolyte binding process increases, which leads to suppression of the formation of loose heterogeneous coacervate particles of (bio)PEC.

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Direct conversion of solar energy into thermal energy by photothermal materials is the most efficient method among all solar energy conversion strategies. In this research, the photothermal performance of functionalized carbon nanotubes (CNTs) was investigated in both visible and near-infrared (NIR) regions (300–1000 nm), and their ability to evaporate water and also to kill cancer cells was investigated. CNTs with different concentrations of 0.03, 0.06, 0.25, and 0.5 g/L were dispersed in deionized water, and a maximum increase in the water temperature of 15 °C was measured in visible light. Also, a water surface evaporation rate of 0.6336 kg/h.m² with the photothermal conversion efficiency of 70.4% in the visible range was measured. The photothermal performance of CNTs in the NIR region was investigated with 808 nm laser radiation, and a water temperature increase of 46 °C with a conversion efficiency of 40.37% was measured. By increasing the laser power from 1 to 2 W/cm², the water temperature reached to 100 °C in less than 6 min. Also, the photothermal therapy performance of CNTs in killing HeLa cancer cells was investigated by the MTT method and found that CNTs can kill 93% of HeLa cancer cells within 10 min under laser radiation.‌

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The excellent electrical properties of tetrafluoroethylene-propylene elastomer (FEPM) rubber make it widely used in electrical insulation materials. In this study, density functional theory is employed to investigate the microstructural and space charge characteristics changes of FEPM rubber under an external electric field. The results demonstrate that as the electric field intensity increases, the total energy decreases while the dipole moment and polarizability increase, leading to a decrease in the stability of FEPM. The molecular chains undergo elongation under tension, leading to a reduction in the stability of their geometric structure, thereby impacting their mechanical and electrical properties. Furthermore, at higher electric field intensities, there is a decrease in the front orbital energy gap accompanied by an increase in conductivity. Simultaneously, there is a shift in active sites for molecular chain reactions and the formation of energy level distribution for hole traps and electron traps along the front track of molecular chains, making it easier for FEPM to capture injected space charges. When reaching a critical value of 14.6547 V/nm, the molecular structure of FEPM undergoes destruction with significant changes observed in its infrared spectrum. It offers theoretical backing for the direction of material modification, high voltage breakdown testing, and assessment of the insulation state.

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Sodium salt of ibuprofen (IBF) drug, a non-steroidal anti-inflammatory, and TX-165 nonionic surfactant mixture with diverse mole fraction (α₁) of TX-165 at a temperature of 298.15 K was investigated by the tensiometry method to evaluate dissimilar physico-chemical characteristics. UV–visible spectroscopy was also utilized to determine the interactions amongst IBF and TX-165. The interaction amongst IBF and TX-165 was also assessed employing 100 mmol·kg⁻¹ NaCl and 500 mmol·kg⁻¹ urea solvents other than the aqueous solution. Ideal cmc (cmc^id) value of mixed systems (IBF + TX-165) achieved by tensiometric measurements was remarkably over the critical micelle concentration (cmc) value. Accordingly, it was validated that IBF and TX-165 interact well, and interaction also rises due to an increase in TX-165’s α₁. The cmc values for entire singular and mixtures of urea media were higher compared with those for aqueous system, while in NaCl media, they were much lower than those for aqueous systems. Clint, Motomura, Maeda, and Rubingh, hypothetical models have been applied to reveal aggregation and thermodynamic properties. Employed ingredients activity coefficients for micellar solutions were always under one, demonstrating the nonideal behaviour together with intermolecular interactions amongst ingredients. As a result of the obtained excess free energy being negative in all cases, the mixed micelles have more stability than their singular ingredients’ micelles. Interaction amongst IBF and TX-165 with each other was also attained well through a UV–visible study. According to the results, TX-165 has the potential to be an applicable ingredient for the delivery of drugs.

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In this study, cotton waste (white and green) from the textile brushing process and cotton wool were used as raw materials to obtain regenerated cellulose films. Cellulose was dissolved with the ionic liquid 1-ethyl-3-methylimidazolium chloride [EMIM]Cl at temperatures of 110, 120, and 130 °C. The dissolution process was evaluated by polarized light microscopy which demonstrated that at lower temperatures (110 °C and 120 °C), the dissolution is preceded by swelling, whereas at 130 °C, rapid fragmentation of the fibers occurs. The presence of dye in cotton fiber extended the dissolution time. After dissolution at 110 °C and regeneration in a water bath, the films obtained were smooth and homogeneous and preserved the color of the residue. Characterization by X-ray diffraction (XRD) and Fourier transform-infrared spectroscopy (FTIR) indicated a transition from crystalline type I cellulose in the cotton samples to an amorphous structure in the regenerated films. The thermogravimetric analysis (TGA) revealed that films showed lower thermal stability than cotton fibers, attributed to cellulose depolymerization. The cotton source did not significantly affect the mechanical properties of the films, which had tensile strength ranging from 25.8 to 33.4 MPa and elongation at break between 14.7 and 19.7%. Overall, textile residues can be used without prior treatment to produce either transparent or intrinsically colored films with potential for application in various fields.

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