Kinetics of High Density Functional Polymer Nanocomposite formation by Tuning Enthalpic and Entropic Barriers

High density functional polymer nanocomposites (PNCs) with high degree of dispersion have recently emerged as novel materials for various thermo-mechanical, optical and electrical applications. The key challenge is to attain...

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.

Determination of optimal parameters of vibrо-activation of hydrated lime

The method of mechanical activation of hydrated lime in a vibrating activator of bunker type was offered in this work. The influence of design features and angle of fixing of vibrating blades on the speed and degree of dispersion of hydrated lime was investigated by measuring the change in the logarithmic decrement of mass attenuation during vibro-activation. The effect of the duration of the vibro-activation process on the dispersion in the system "hydrated lime–water" was studied. The efficiency of lime dispersion was shown in the case of mounting the blades at the angle of 860 for 40–60 minutes. Comparative studies of the strength of cement stone showed that the addition of vibro-activated hydrated lime in an amount of 2 wt.% leads to an increase in the strength of lime-cement compositions.

Research on the Spatio-temporal Differences in the Living Standards of the Counties under the Shandong Province

Using the method of district statistics to verify the correlation of NPP-VIIRS night light data and GDP, the difference between counties in Shandong from 2012 to 2019 can be analysed and the changes of living standards can be quantified. After obtaining the total value of night light brightness in each county, the coefficient of variation is used to calculate the degree of dispersion of each county, and then the regional differences of each city in 2019 and the inter-annual changes from 2012 to 2019 are analyzed and displayed. In conclusion, living standards of different countries in Shandong are different, and the difference becomes obvious with the growth of GDP. However,the difference of living standards of most countries becomes smaller in recent years.

INVESTIGATION OF RHEOLOGICAL PROPERTIES OF HYDROXYAPATITE AND FLUORAPATITE IN COLLOIDAL STATE

В статье обсуждается возможность практического применения суспензии гидроксиапатита и фторапатита в качестве компонентов лекарственных средств, фармацевтических композиций и биоматериалов. С использованием физикохимических методов анализа оценены их вязкость, плотность и степень дисперсности. Определены концентрационные интервалы, в которых исследуемые системы обладают свойствами, необходимыми для создания фармацевтических композиций и биоматериалов. Биологическая активность апатитов во многом зависит от степени дисперсности и проявляется тем больше, чем меньше размер их частиц, а полученные в данной работе наночастицы гидроксиапатита и фторапатита в суспензиях имеют размер частиц порядка менее 100 нм, и, следовательно, реологические свойства у них проявятся наиболее полно. The article discusses the possibility of practical application of a suspension of hydroxyapatite and fluorapatite as components of medicines, pharmaceutical compositions, and biomaterials. Their viscosity, density and degree of dispersion were estimated by using the physical and chemical analysis methods. The concentration intervals in which the studied systems have the properties necessary for creating pharmaceutical compositions and biomaterials are determined. The biological activity of apatites largely depends on the degree of dispersion and manifests itself the more, the smaller the size of their particles, and the obtained in this work nanoparticles of hydroxyapatite and fluorapatite in suspensions have a particle size of the order of less than 100 nm, and, consequently, their rheological properties will be most fully manifested.

Essential Nanostructure Parameters to Govern Reinforcement and Functionality of Poly(lactic) Acid Nanocomposites with Graphene and Carbon Nanotubes for 3D Printing Application

Poly(lactic) acid nanocomposites filled with graphene nanoplatelets (GNPs) and multiwall carbon nanotubes (MWCNTs) are studied, varying the filler size, shape, and content within 1.5–12 wt.%. The effects of the intrinsic characteristics of nanofillers and structural organization of nanocomposites on mechanical, electrical, thermal, and electromagnetic properties enhancement are investigated. Three essential rheological parameters are identified, which determine rheology–structure–property relations in nanocomposites: the degree of dispersion, percolation threshold, and interfacial interactions. Above the percolation threshold, depending on the degree of dispersion, three structural organizations are observed in nanocomposites: homogeneous network (MWCNTs), segregated network (MWCNTs), and aggregated structure (GNPs). The rheological and structural parameters depend strongly on the type, size, shape, specific surface area, and functionalization of the fillers. Consequently, the homogeneous and segregated network structures resulted in a significant enhancement of tensile mechanical properties and a very low electrical percolation threshold, in contrast to the aggregated structure. The high filler density in the polymer and the low number of graphite walls in MWCNTs are found to be determinant for the remarkable shielding efficiency (close to 100%) of nanocomposites. Moreover, the 2D shaped GNPs predominantly enhance the thermal conductivity compared to the 1D shaped MWCNTs. The proposed essential structural parameters may be successfully used for the design of polymer nanocomposites with enhanced multifunctional properties for 3D printing applications.

Influence of recrystallization annealing regime on the formation of a fine-grained structure in structural steels

The analysis of the main factors affecting the reliability and safety of welded metal structures in long-term operation is carried out. The features of obtaining a fine-grained structure due to recrystallization annealing and the main factors affecting the degree of dispersion of the formed microstructure are considered. For low-carbon steel 08ps and low-alloy steel 09G2S, optimal recrystallization annealing regimes have been developed with the aim of obtaining final structures with a given degree of dispersion, typical for real building metal structures. It was found that the degree of dispersion of the obtained microstructures depends on the heating temperature, the initial structure, and the chemical composition of the steels.