Formation Of Dispersed Particles Research Articles

Solvothermal Fabrication of Mesoporous Pd Nano-Corals at Mild Temperature for Alkaline Hydrogen Evolution Reaction.

Porous metallic nanomaterials exhibit interesting physical and chemical properties, and are widely used in various fields. Traditional fabrication techniques are limited to metallurgy, sintering, electrodeposition, etc., which limit the control of pore size and distribution, and make it difficult to achieve materials with high surface areas. On the other hand, the chemical preparation of metallic nanoparticles is usually carried out with strong reducing agents or at high temperature, resulting in the formation of dispersed particles which cannot evolve into porous metal. In this study, we reported the simple fabrication of coral-like mesoporous Pd nanomaterial (Pd NC) with a ligament size of 4.1 nm. The fabrication was carried out by simple solvothermal reduction at a mild temperature of 135 °C, without using any templates. The control experiments suggested that tetrabutylammonium bromide (TBAB) played a critical role in the Pd(II) reduction into Pd nanoclusters and their subsequent aggregation to form Pd NC, and another key point for the formation of Pd NC is not to use a strong reducing agent. In alkaline water electrolysis, the Pd NC outperforms the monodisperse Pd NPs and the state-of-the-art Pt (under large potentials) for H2 evolution reaction, probably due to its mesoporous structure and large surface area. This work reports a simple and novel method for producing porous metallic nanomaterials with a high utilization efficiency of metal atoms, and it is expected to contribute to the practical preparation of porous metallic nanomaterials by solvothermal reductions.

Systematic assessment road network impact on atmosphere of urbanized area

Introduction. To study the urbanized territory as a system, an approach was used that allows assessing gaseous and dispersed atmospheric pollution using a unified scale of environmental hazard. The features of air pollution in urban areas were considered, where a significant number of stationary and mobile sources of negative environmental impact are concentrated in limited overpopulated areas.The purpose of the study. the use of theoretical foundations for a systematic assessment of the level of environmental hazard of an urbanized area under the influence of the road network due to a combination of gaseous and dispersed atmospheric pollution.Methods and materials. Based on the improved model of the Urbanized Territory system, the following hypothesis is proposed: 1) motor traffic flows are both independent sources of formation of dispersed particles and sources of uplifting and spreading of particles, which in the presence of gaseous pollutants increases the level of environmental hazard of atmospheric pollution in an urbanized area; 2) atmospheric pollution of an urbanized area is formed when gaseous pollutants and dispersed particles from the street and road network are superimposed on the polluting background of other elements of the Urbanized territory system.Results. The distribution maps of the calculated complex index of atmospheric pollution were obtained for the most problematic areas of the urbanized territory of Naberezhnye Chelny - Prospekt Mira and Kazansky Prospekt. The obtained results characterize the change in the level of environmental hazard of urbanized areas when gaseous pollutants and dispersed particles from the street and road network are superimposed on the polluting background of other elements of the Urbanized territory system.Discussion and conclusion. Based on the generalization and comparison of the results of previous and current studies of the authors, comparing them with the results of other researchers, the hypothesis was fully confirmed. Conclusion. With the confirmation of the hypothesis, the goal of the study was achieved, which has scientific novelty and practical significance for the arrangement of a favorable and comfortable urban environment.

Особенности загрязнения воздуха дисперсными частицами урбанизированной территории «ИнноКам»

The combination of factors that determine the level of atmospheric pollution, the priority harmful component of which is dispersed particles, has a random and unique character for the urbanized territory of «InnoKam». Therefore, to study the process of atmospheric pollution of this urbanized territory, an approach was used that takes into account that the content in the air of dispersed particles of motor transport and industrial origin depends on the nature of the processes of upsurge, propagation and deposition, which are determined by the fractional composition of particles, structural and functional parameters of road traffic flows., climatic and urban features of the territory and meteorological conditions. The aim of the study is to reveal the patterns of air pollution in the urbanized territory of «InnoKam» with dispersed particles, which is relevant and necessary for the effective implementation of measures to create a favorable and comfortable urban environment, as well as the attractiveness of the innovation and production center for visiting specialists and investors. Regularities of air pollution in the urbanized territory of «InnoKam» by dispersed particles, which is formed when pollution from road traffic flows are superimposed on the polluting background of industrial enterprises, have been investigated. Motor transport streams are both independent sources of the formation of dispersed particles, and a source of upsurge and spread of dispersed particles over considerable distances beyond the boundaries of highways. To reveal the regularities and obtain the corresponding mathematical models, both instrumental methods based on measuring the content of dispersed particles DCh 10 and DCh 2.5 in the atmosphere of the investigated urbanized territory, and statistical analysis of experimental data were used. Mathematical models have been obtained that, with a high degree of reliability, describe the regularities of air pollution by dispersed particles for the urbanized territory of «InnoKam», which is the scientific value of the results obtained. The practical significance of the results obtained lies in their use for predicting and compiling air pollution maps with dispersed particles in all parts of the urbanized territory of «InnoKam» in order to develop and substantiate measures to create a favorable and comfortable urban environment. The main activities are analyzed and divided into three groups, based on the specifics of the sources of formation of dispersed particles (vehicles, traffic flows, highways). The ranking of measures for the effectiveness of reducing air pollution by dispersed particles is the object of further research.

Нейтронографическое исследование кинетики низкотемпературного распада мартенсита среднеуглеродистой стали

It is found that the low-temperature decomposition of martensite in quenched medium-carbon steel occurs in two stages. In the first stage, the rate of decomposition is higher than that in the subsequent stage. Application of the neutron diffraction method allows the identification of two stages of transformation in the first stage of martensite decomposition. It is shown that the first stage is associated predominantly with carbon segregation at dislocations, and the second, with the outdiffusion of carbon from the supersaturated solid solution with the formation of dispersed particles of metastable carbides. It is shown that the change in the concentration of carbon and, accordingly, the degree of tetragonal lattice of martensite at aging and low tempering occurs to a certain limit, independent of the cooling rate during quenching and tempering temperature. This is due to the establishment of a relative equilibrium between a supersaturated solid solution and fine particles of metastable iron carbide. It is found that the determining process, which leads to a change in the microhardness the low-temperature decomposition, is the out diffusion of carbon from the supersaturated solid solution.

Development and Research of Flux-Cored Electrodes For Welding And Surfacing Of Parts From Aluminum And Titanium Alloys

Perpose of research was to study the properties of powder materials obtained from aluminum and titanium waste by the method of electroerosion dispersion for the development of electrodes suitable for welding and surfacing of parts from aluminum and titanium alloys. Methods . To obtain an aluminum powder material by electroerosion dispersion method, an aluminum wire GOST 14838-78 was used, pre-cut to 5-7 cm. the Wire was loaded into a reactor filled with a working liquid – distilled. The process was carried out at the following electrical parameters: discharge capacitor capacity 65 UF, voltage 100 V, pulse frequency 100 Hz. To obtain a titanium powder material by electroerosion dispersion method, shavings of VT6 grade were used. The chips were loaded into a reactor filled with a working liquid – distilled water. The process is carried out at the following electrical parameters: capacity of the bit capacitors 65 µf, a voltage of 150 V, pulse frequency of 250 Hz. The result of the local effects of intermittent electrical discharges between the electrodes was the destruction of the material with the formation of dispersed particles of powder. In order to study the shape and morphology of powder material particles obtained by electroerosion dispersion from aluminum waste, images were taken on a raster (scanning) electron microscope QUANTA 600 FEG. The study of granulometric composition of powder materials obtained by the method of electroerosion dispersion of aluminum and titanium waste was carried out on a laser analyzer particle size Analysette 22 NanoTec. Results. It is established that the most promising and not industrially used materials for the production of electrodes used in welding and surfacing of parts are powder materials obtained by electroerosion dispersion. It is experimentally established that the powder materials obtained by electroerosive dispersion of aluminum and titanium wastes consist of spherical and elliptical particles. The results of the study of the elemental composition of powder materials obtained by electroerosive dispersion of aluminum and titanium waste, it is shown that the main elements of the powders produced and aluminum waste are aluminum and oxygen, and the main elements of the powders produced and shavings of the VT6 BRAND are Ti, Al, O, V, Fe, W and K. Studies of the particle size distribution of powder materials obtained by electroerosion dispersion showed that the average particle size of powders obtained from aluminum waste is 19.08 microns, and the average particle size of powders obtained from titanium waste is 33.12 microns. It is established that the most promising method for the production of electrodes used for welding and surfacing of parts from aluminum and titanium alloys is the method of spark plasma sintering. Conclusion . The obtained results can be used to create resource-saving processes for processing metal alloys and composite materials.

Methods for extraction of mercury compounds from coal in Ukraine

The ways of prevention of environmental pollution by coal-containing mercury compounds are investigated in the paper. Coal mercury compounds are harmful and toxic impurities. In coal, the mercury is in the form of sulfides and mercury-containing organic compounds. Considerable amounts of native mercury and cinnabar are also recorded. The content of the mercury in terms of metal in the Donbass coal ranges from 0.01 to 1000 g / t. The highest concentrations of mercury compounds are due to hydrothermal and volcanic processes. In Donbass coal, the content of mercury compounds is on average 5 to 10 times greater than the background compared to other coal basins. The most common form of mercury compounds in coal are impurities in sulfide minerals. The content of mercury compounds in pyrite is two orders of magnitude higher than in the organic coal component. It is established that the bulk of the mercury compounds are contained in fine particles. The maximum content is fixed in a fraction of 0.1 - 15 microns. Thus, it can be assumed that the mercury compounds are predominantly contained in the mineral component of coal, which is more intensively ground. It is shown that washing with hot water and the complexing agent solution results in a decrease in the content of mercury compounds in the coal feedstock. The washing solutions become turbid, and this suggests that the mercury compounds are flushed out with fine particles. The increase in the degree of extraction of compounds of the mercury when applying the complexing solution is due to the ability of aurintricarboxylic acid to form complex compounds with the mercury ions. It can be assumed that in this case chemisorption occurs with the formation of complex compounds of the chelate structure on the surface of the particles, followed by dispersion of the particles of the dispersed phase. It was found that washing of the dispersed coal raw material is accompanied by weight loss. This indicates that the mercury compounds are leached from the coal in the form of dispersed particles. Waste sludge is to be disposed of with further disposal.

RESEARCH OF INFLUENCE OF PARAMETERS OF DISPERSION IN THE PARTICLE SIZE COBALT POWDERS ARE OBTAINED FOR ADDITIVE TECHNOLOGIES EDM DISPERSION IN ALCOHOL

Currently, there is a need of adaptation of the Russian production of powders and market metal-powder compositions under the conditions and requirements of modern installations additive 3D technologies. Based on the characteristics of the methods of obtaining spherical powders with the aim of obtaining spherical granules of the regulated grain technology offers electroerosion dispersion characterized by relatively low energy costs and environmental cleanliness of the process. The main advantage of the proposed technology is the use as raw materials waste, which is much cheaper than the pure components used in traditional technology. In addition, this technology allows to vary the granulometric composition of the obtained powder by changing electrical parameters. The aim of this work was to study the impact of dispersion on the particle size cobalt powders are obtained for additive technologies electroerosion dispersing in alcohol. For the proposed studies selected waste cobalt alloy brand CHMS "CELLET". As working fluid - a isobutyl alcohol. To obtain cobalt powders by the method of electroerosion dispersion used for the installation of AED dielectric materials. Waste was loaded into the reactor filled with the working liquid isobutyl alcohol, the process is carried out at the following electrical parameters: capacitance of the discharge capacitor 48 microfarads; pulse frequency 80 Hz; voltage: 100 (sample 1); 120 (sample 2); 140 (sample 3). The result of the local effects of intermittent electrical discharges between the electrodes was the destruction of the waste material with the formation of dispersed particles of powder. Granulometric composition of the obtained powders were investigated using the device Analysette 22 NanoTec . The results of the research aimed to study the impact of dispersion on the particle size cobalt powders are obtained for additive technologies EDM by dispersion in alcohol, it was found that when the voltage on the electrodes of 100 V, 120 V, 140 V, the average particle size is microns of 27.09, 31,59 33,61 µm and µm, respectively.

Evaluation of fat grains in gothaj sausage using image analysis

Fat is an irreplacable ingredient in the production of sausages and it determines the appearance of the resulting cut to a significant extent. When shopping, consumers choose a traditional product mostly according to its appearance, based onwhat they are used to. Chemical analysis is capable to determine the total fat content in the product, but it cannot accurately describe the shape and size of fat grains which the consumer observes when looking at the product. The size of fat grains considered acceptable by consumers can be determined using sensory analysis or image analysis. In recent years, image analysis has become widely used when examining meat and meat products. Compared to the human eye, image analysis using a computer system is highly effective, since a correctly adjusted computer program is able to evaluate results with lower error rate. The most commonly monitored parameter in meat products is the aforementioned fat. The fat is located in the cut surface of the product in the form of dispersed particles which can be fairly reliably identified based on color differences in the individual parts of the product matrix. The size of the fat grains depends on the input raw material used as well as on the production technology. The present article describes the application of image analysis when evaluating fat grains in the appearance of cut of the Gothaj sausage whose sensory requirements are set by Czech legislation, namely by Decree No. 326/2001 Coll., as amended. The paper evaluates the size of fat mosaic grains in Gothaj sausages from different manufacturers. Fat grains were divided into ten size classes according to various size limits; specifically, 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 5.0, 8.0 and over 8 mm. The upper limit of up to 8 mm in diameter was chosen based on the limit for the size of individual fat grains set by the legislation. This upper limit was not exceeded by any of the products. On the other side the mosaic had the hightest representation of 0.25 mm fat grains.

Neutron diffraction study of the kinetics of low-temperature martensite decomposition in medium-carbon steel

It is found that the low-temperature decomposition of martensite in quenched medium-carbon steel occurs in two stages. In the first stage, the rate of decomposition is higher than that in the subsequent stage. Application of the neutron diffraction method allows the identification of two stages of transformation in the first stage of martensite decomposition. It is shown that the first stage is associated predominantly with carbon segregation at dislocations, and the second, with the outdiffusion of carbon from the supersaturated solid solution with the formation of dispersed particles of metastable carbides.

Homogenization conditions and mechanical properties of ingots of calcium-doped AV alloy

The influence of calcium microalloying on the homogenization temperature of ingots of AV grade alloys of the Al–Mg–Si–Cu system is studied. It is shown that, to provide the maximum dissolution of excess phases, the homogenization temperature of ingots should be chosen in a range of 560–575°C. The microstructure of ingots of the calcium-doped AV alloy has two types of phase components over boundaries of dendrite cells: light skeleton-like and dark compact round shapes. The calcium microalloying additive results in the formation of dispersed particles of excess intermetallide phases in the AV alloy with variable composition of AlxSiyCa and AlxSiyMgzCa, which promote nucleation of new grains. It is likely that calcium as the surfaceactive element changes the contribution of grain-boundary energy. This is the constraint for collective recrystallization.

Effect of Alloying on the Structure and Mechanical Properties of Hot-Forged Aluminum-Matrix Powder Composites Al–Ti–C

The data of structural and phase analysis of the master alloys produced by thermal synthesis from three compositions of Al–Ti–C powder mixtures are presented. It is shown that depending on the content ratio of titanium and carbon, the heating of the mixture leads to in situ formation of dispersed particles of titanium carbide TiC or complex titanium-aluminum carbides. Aluminum matrix composites with titanium carbide phase as reinforcement are produced by hot forging using synthesized master alloys. It is established that an increase in the carbide content entails an increase in the strength and hardness of composites, while ductility decreases. Therefore, the hardness and strength properties of the composites produced from a charge prepared in a drum tumbler mixer are significantly lower than those of samples produced from a charge prepared in a planetary mill, whereas the ductility of the latter is slightly lower.

Modeling of reactive gas–solid flows in riser reactors using a multi-scale chemical reaction model

For gas–solid riser reactors, the multi-scale structure involving a dilute phase in the form of dispersed particles and a dense phase in the form of clusters is a significant feature. Many recent studies have focused on the development of the inter-phase drag coefficient model for the heterogeneous gas–solid flow. However, the impact of the meso-scale structure on mass transfer and chemical kinetics is important for reactive systems. In this work, we extend the multi-scale approach to an n-order irreversible chemical looping reaction and the influence of clusters on chemical reaction is investigated. The local structural parameters can be provided using a modified cluster structure-dependent (CSD) drag coefficient model. The concentrations of gas species in the cluster, the disperse particle and the interface are obtained. The inter-phase mass transfer between the dispersed phase and the cluster phase is evaluated.

Flocculation and flotation response of Rhodococcus erythropolis to pure minerals in hematite ores

Rhodococcus erythropolis as a flotation collector for hematite was evaluated in the study. The surface morphology and cell wall composition of R. erythropolis was analyzed. Zeta potentials for four pure minerals from hematite ores were measured before and after adsorption by R. erythropolis. Pure mineral flotation tests and mixed mineral separation tests were performed to describe adsorption characteristics and mechanisms. A rod-shaped bacterium was detected with CH2, CH3 and COO groups on its cell wall that imparted hydrophobicity and negative charges. The ability of R. erythropolis to collect hematite was stronger than its ability to collect quartz, kaolinite and apatite. For a pulp pH of 6 and a cell concentration of 75mg/L, recovery rate of hematite was 89.67%. The recovery differences between hematite and quartz, kaolinite and apatite were 66.43%, 60.36% and 54.30%, respectively. These data indicated that electrical properties of hematite surface were more suitable for adsorption of R. erythropolis than other three minerals. The adsorbed hematite particles appeared as large agglomerates after interaction with R. erythropolis. The quartz, kaolinite and apatite particles, however, were in the form of dispersed particles or small agglomerates. The chemical adsorption of hematite on bacterial cell wall resulted in agglomeration. The effects of flocculation and flotation of R. erythropolis on micro-fine hematite particles were characterized for the first time. The results showed that R. erythropolis can act as a flotation collector for hematite from hematite ores.

Cold rolled nanostructured super-pure Al (99.9996 %) containing 1 % Si particles: structure and strength

A nanostructured Al-1 % Si alloy has been produced using extremely high purity Al (99.9996 %) containing 1 % Si present in the form of dispersed particles. The Si particles stabilize the structure and prevent recrystallization during cold rolling, which has been carried out to a very high strain \( (\varepsilon_{\text{vM}} = 4.5) \). The microstructure, strength, and ductility are characterized and the observations are analyzed and discussed focusing on effects of matrix purity and particles in a fine dispersion.

PNIPAM microgels for biomedical applications: from dispersed particles to 3D assemblies

Poly(N-isopropylacrylamide) (PNIPAM) microgel is perhaps the most well-known intelligent soft nanomaterial. Combining the strengths of hydrogel and nanoparticles, with unique stimuli-responsivity, PNIPAM microgels have found numerous biomedical applications, such as drug delivery, biosensing, and so on. Usually they were used as dispersed particles, however, they can also be used as building blocks to fabricate 2D films and 3D aggregates. These nanostructured assemblies exhibit new properties which the dispersed particles do not have, and new biomedical applications have been found for these assemblies. In this paper, the biomedical applications of PNIPAM microgels in the form of dispersed particles, 2D films and 3D aggregates were reviewed and some recent progress in this area was highlighted.

Synthesis and characterization of Rh and RhO particles supported on zeolites with high activity of lean NO –CO–H2 reaction

Rh and RhO x nanoparticles supported on zeolites were synthesized in a hydrothermal process using a gel mixture of zeolite and Rh precursors. The morphology of the nanoparticles was varied depending on the kind of zeolite and synthesis conditions. Samples were characterized with XRD, TEM, CO chemisorption and BET analysis. In the hydrothermal process, the nanoparticles were loaded on Na-beta zeolite and Na-ZSM-5 in the form of dispersed particles and agglomerated particles, respectively. The nanoparticles supported on Na-ZSM-5 more efficiently catalyze NO x reduction in lean conditions using hydrogen and CO as a main reductant than those supported on Na-beta zeolite.

Borides of Ag and Au prepared by magnetron sputtering

Following the discovery of MgB 2 that has a superconductive critical temperature ( T c) of ∼39 K much research was initiated in the search for materials with higher T c. Theoretical studies predicted that diborides of metals having the AlB 2 type structure, among them AgB 2 and AuB 2, may be superconductive at values of T c even higher than 39 K. In our attempts to prepare AgB 2 and AuB 2 using films of the Ag–B and Au–B systems, no superconductivity was observed. Equilibrium phase diagrams of these systems do not support the possibility of forming AgB 2 or AuB 2 compounds, despite a report which indicates their existence. Films of the Ag–B and Au–B systems were obtained by magnetron cosputtering from two separate targets, that of B and Ag (or Au) on Si(1 0 0) substrates in Ar ambient. The specimens were subjected to X-ray diffraction (XRD), secondary electron microscopy (SEM), X-ray photo spectroscopy (XPS), Auger analysis and optical microscope (OM) investigations. No superconductivity was observed in the range 10–200 K on the basis of resistivity measurements. The films were not homogeneous, but rather the alloys had decomposed into two separate phases. One of the phases was in the form of dispersed particles. An XRD peak at 28° was observed which supposedly is characteristic of a noble metal boride. The possibility that the XRD peaks might belong to a boric acid phase also exists. The boric acid phase had the same diffraction peak as was observed by XRD in our films.

Formation of dispersed particles during plasma oxidation

Microplasma oxidation is a promising method of producing ceramic coatings for various purposes [1–5]. At present theoretical models of breakdown and coating growth are being actively developed and new application areas suggested [6–8]. We already know the mechanisms of growth of microplasma coatings due to electrochemical and chemical oxidation of metals and inclusions of electrolyte elements in the course of thermal reactions on the surface [9]. In the place of microarc discharge on the solutionmetal interface during a short period of time (about 200–1000 μs) high temperatures of 103–104 K and pressure of 102–103 MPa are developed [10] which result in the formation of a vapor-gaseous medium in the space and the local fusing of the base metal, which is ejected by the arc process into the solution where part of it is hydrated and the rest of it remains there in ionic form [11]. The present article shows additional mechanisms of inclusion of electrolyte components into the microplasma coating composition as a result of crystal formation in the electrode layer. Specimens of 2024 aluminium alloy (4.4% Cu, 0.6% Mn, 1.5% Mg) with a total area of 0.02 dm2 served as anode. They were first etched in potassium hydroxide solution and then purified in nitric acid solution. A plate of stainless steel 3 dm2 in area, served as a cathode. The treatment was carried out in electrolyte based on sodium phosphate (20 g·l−1) with inclusions of ferrous citrate (10 g·l−1) and surface—active substances (triethylolamine 15 g·l−1). A potentiostatic processing regime with unipolar sinusoidal or pulse voltage ranging from 300 to 520 V was used. The coating formation time took from 20 to 40 min, with an electrolyte temperature of 298–318 K. The micrographs and the element composition data on the coatings were obtained using a JSM 84 scanning electron microscope with a link adapter at the magnification of 1000 times. Average concentrations of components were obtained from an area of 200 × 200 μm using three measurements. The concentrations in the crystal region were determined by focusing a beam to 5 μm in size. A morphology study of the surface after microplasma processing has revealed, in a number of cases, dispersed formations on the coating, including those of a regular geometric shape (Fig. 1). It indicates the crystalline nature of the above structures. The presence of dispersed particles on the coating surface is caused by the characteristic features of microarc oxidation. Ejection of melt, which accompanies a breakdown, and its interaction with electrolyte, result in the formation of both fused parts around pores and various dispersed particles of the amorphous structure weakly connected to the surface. Crystallisation on the coating surface under given physical conditions (high temperatures and pressures ) is unlikely. The formation of crystals deep in the solution is also highly improbable as it is not supersaturated in any component, and is heated during the microplasma process. In order to explain the mechanism of appearance of dispersed formations of a crystalline structure, the following approach has been suggested. When a unipolar electric current passes through the specimen surface, intensive decomposition of water occurs:

Formation of dispersed particles composed of soybean oil and phosphatidyl choline

AbstractThe purpose of this study was to investigate the dispersal mechanism of soybean oil (SO) in phospholipids to form a fat emulsion. SO was dispersed with soybean phosphatidyl choline (PC) using sonication. The dispersal mechanism was evaluated by characterizing the dispersed particles using dynamic light scattering, fluorescence spectroscopy and surface monolayer techniques. The dispersions in SO fractions being in the range of 0.1‐0.7 were stable at room temperature for 3 d. A limited amount of SO was incorporated into PC bilayer membranes. The excess SO separating from the PC bilayers was stabilized as emulsion particles by the PC surface monolayer. When the PC content was lower (SO more than 0.8 mol‐%), the PC monolayer did not completely cover the hydrophobic SO particle surfaces. In this case, the particle size increased drastically and the separation into oil and water occurred. Therefore, the solubility between SO and PC and the coexistence of emulsion and liposomal particles are critical parameters for the stabilization of the particles in water.

Toughening of polystyrene and poly(phenylene oxide) matrices with elastomeric styrene‐based block copolymers: Role of molecular architecture

AbstractThe effects of the molecular architecture of elastomeric styrene‐based block copolymers on efficiency of toughening a brittle (polystyrene) and a ductile [a miscible blend of 80% phenylene oxide copolymer and 20% polystyrene (80PEC)] polymer were explored experimentally. Toughening appears to be mainly controlled by the blend morphology, which is determined by the rheological characteristics of the block copolymer relative to that of the matrix. The formation of dispersed particles during melt blending in a Brabender Plasticorder is strongly influenced by the ratio of the matrix and block copolymer viscosities (estimated here by Brabender torque). The size of the dispersed particles was found to be proportional to the 1.77 power of the torque ratio when this ratio is greater than unity. Thus, to a first approximation the effect of block copolymer architecture on toughening efficiency is related to how this structure affects the rheological behavior of the copolymer. Excellent toughness of polystyrene was achieved when the particle size was larger than 1–2 μm. The 80PEC resin is best toughened by block copolymers that form a cocontinuous phase morphology. The extent of toughening of this matrix appears to be a strong function of the styrene block molecular weight, whereas this structural feature seems to have no significant effect in toughening polystyrene.