РЕГУЛЮВАННЯ СТІЙКОСТІ РІДКИХ МІКРОСТРУМЕНІВ ПОЛІПРОПІЛЕНУ В МАТРИЦІ СПІВПОЛІАМІДУ ЗА РАХУНОК НАНОДОБАВОК

Goal. Investigation of the effect of the concentration of nanoparticles of aluminum oxide (Al2O3) and alumina modified with silver (Ag/Al2O3) on the decomposition kinetics of liquid microjets of polypropylene (PP) in a copolyamide (CPA) matrix and the possibility of controlling the microfibrillar morphology of the PP/CPA blend.Methodology. The components of the blend were mixed on a screw-disk extruder. The kinetics of the disintegration of liquid microjets was studied using a technique based on the theory of destabilization of a liquid cylinder under the action of capillary waves. The degree of dispersion of polypropylene in the matrix was evaluated by photomicrographs of cross sections of the extrudates of the blends.Results. Nanoadditives of the original and silver-modified aluminum oxide with a content of (0.1 ÷ 3.0) wt.% In the blend increase the compatibility of the components: the surface tension (γαβ) in the compositions of all compositions decreases. Ag/Al2O3 nanoparticles are more effective than aluminum oxide nanoparticles - the γαβ value decreases by 9.6 and 5.3 times, respectively, which ensures a high degree of dispersion of the dispersed phase component in the matrix. The disintegration resistance of polypropylene microjets is increasing, as evidenced by a decrease in the instability coefficient (q) and an increase in the microjet lifetime (tl). The curves of q and tl dependence on the additive content have an extreme character. The minimum values of the instability coefficient of microjets and the maximum values of their lifetime are achieved at a nanoparticle concentration corresponding to the lowest interfacial tension.Scientific novelty. The positive effect of the investigated nanoadditives on the kinetics of the decomposition of liquid microjets of polypropylene in the copolyamide matrix has been established. The highest modifying effect in the presence of Ag/Al2O3 nanoparticles is due to their amphiphilic nature, which ensures the predominant localization of nanoparticles at the interface and a synergistic increase in the degree of compatibility in the PP/CPA system.Practical significance. The regularities of increasing the stability of liquid microjets to disintegration in polymer blends filled with nanoparticles have been established, which will make it possible to determine the parameters of the processes of mixing and forming fibers and films, in which the microfibrillar structure arising during the flow of the melt will remain unchanged in the products.

Analysis of the effect of ultrasonic vibration on nanofluid as coolant in engine radiator

The paper discusses the combined methods of increasing heat transfer, effects of adding nanofluids and ultrasonic vibration in the radiator using radiator coolant (RC) as a base fluid. The aim of the study is to determine the effect of nanoparticles in fluids (nanofluid) and ultrasonic vibration on the overall heat transfer coefficient in the radiator. Aluminum oxide nanoparticles of 20–50 nm in size produced by Zhejiang Ultrafine powder & Chemical Co, Ltd China were used, and the volume concentration of the nanoparticles varied from 0.25 %, 0.30 % and 0.35 %. By adjusting the fluid flow temperature of the radiator from 60 °C to 80 °C, the fluid flow rate varies from 7 to 11 lpm. The results showed that the addition of nanoparticles and ultrasonic vibration to the radiator coolant increases the overall heat transfer coefficient by 62.7 % at a flow rate of 10 liter per minute and temperature of 80 °C for 0.30 % particles volume concentration compared to pure RC without vibration. The effect of ultrasonic vibration on pure radiator coolant without vibration increases the overall heat transfer coefficient by 9.8 % from 385.3 W/m2·°C to 423.3 W/m2·°C at a flow rate of 9 liter per minute at a temperature of 70 °C. The presence of particles in the cooling fluid improves the overall heat transfer coefficient due to the effect of ultrasonic vibrations, nanofluids with a volume concentration of 0.25 % and 0.30 % increased about 10.1 % and 15.7 %, respectively, compared to no vibration. While, the effect of nanoparticles on pure radiator coolant at 70 °C enhanced the overall heat transfer coefficient by about 39.6 % at a particle volume concentration of 0.35 % compared to RC, which is 390.4 W/m2·°C to 545.1 W/m2·°C at 70 °C at a flow rate of 10 liter per minute

Heat insulation effect in solar radiation of polyurethane powder coating nanocomposite

This study aims to improve polyurethane-based coating by modified zirconium oxide and aluminum oxide nanoparticles for preparing thin polymeric heat insulation coatings. In the first step, the nanoparticles were chemically modified with the silane coupling agent. Then, three different weight percent of modified nanoparticles (1, 3, and 5% w/w) were mixed with polyurethane, to prepare the nanocomposites, which were coated on metallic plate samples. Then, these plates are used to measure the radiation heat transfer coefficients, absorption coefficient in a region of short wavelengths (UV/VIS/NIR), the emissivity coefficient, and thermography of the samples in a region of long wavelengths (IR). Results showed that by adding the modified nanoparticles to the polyurethane matrix, absorption was decreased and the emissivity coefficient was increased. According to the thermography results, it was observed that the surface temperature of both samples with 3% w/w of nanoparticles had the minimum temperature compare to others. Minimum heat surface observed for 3% w/w of modified nano zirconium oxide.

Entomotoxic effects of synthesized aluminum oxide nanoparticles against Sitophilus oryzae and their toxicological effects on albino rats

Recently, nanoparticles are emerging as a potential alternative to synthetic pesticides for protection against stored-product insect pests, such as the rice weevil Sitophilus oryzae; however, the toxic effects of nanoparticles on nontarget organisms are not yet understood. Therefore, we investigated the insecticidal effects of synthesized aluminum oxide nanoparticles (Al2O3-NPs) on S. oryzae, as well as their potential toxicity in albino rats. S. oryzae mortality increased as the period of Al2O3-NP exposure increased; 100% mortality was reached at 8000 mg Al2O3-NPs/kg of wheat grain after 7 days of exposure. After 60 days of exposure, all tested Al2O3-NPs concentrations (1000, 2000, 4000, and 8000 mg/kg grain) significantly reduced the number of S. oryzae offspring in a dose-dependent manner. In albino rats, exposure to the LC90 of Al2O3-NPs in a treated diet caused a significant decrease in total body weight and an increase in liver weight in a subacute toxicity test. Moreover, Al2O3-NP treatment elevated the levels of alanine aminotransferase, aspartate aminotransferase, and creatinine in exposed rats relative to control rats, while the uric acid levels of treated rats decreased. Histopathological analysis also revealed various hepatic and renal lesions in treated rats. In summary, although Al2O3-NPs have insecticidal effects, they also have hazardous toxicological effects on rats. Therefore, if Al2O3-NPs are used in the current powder form to protect stored products, they may cause adverse effects to workers and consumers. Further research will be required to develop new nanoformulations with increased safety and potency before these nanoparticles can be used in stored-product pest control.

Enhancement of Solar Water Desalination Using Copper and Aluminum Oxide Nanoparticles

In this research, two identical solar stills were designed and constructed to investigate the effect of adding copper and aluminum oxide nanoparticles on the quantity of water produced by solar desalination. The two solar stills were installed side by side, and measurements were recorded simultaneously from both stills. The nanoparticles were added to one still, each at one time but with different concentrations, while the other contained only water. Data acquisition and a weather station were used to record the glass, water, and ambient temperatures in addition to the hourly solar radiation. It was found that the addition of nanoparticles increases the amount of condensate. The most efficient concentrations were found to be 0.4% of Al2O3 and 0.6% of CuO. At these concentrations, an increase in the efficiency of the still equals 7.8%, and 9.62% was recorded. Furthermore, it was found that CuO has a more pronounced effect on the condensate than Al2O3 at all concentrations except at 0.4% concentration.