Deformation-strength Properties Research Articles

The Influence of Microwave Radiation on the Deformation-Strength Properties of a Polyurethane Binder Based on the PDI-3B Oligomer

The Influence of Microwave Radiation on the Deformation-Strength Properties of a Polyurethane Binder Based on the PDI-3B Oligomer

Investigating the Structure and Properties of Epoxy Nanocomposites Containing Nanodiamonds Modified with Aminoacetic Acid.

This paper presents a study on the prospects of functionalizing nanodiamonds (NDs) with aminoacetic acid to obtain high-strength composites based on an epoxy matrix. The impact of the functionalization of the ND surface with aminoacetic acid in various concentrations on the properties of the epoxy composite was assessed. The success of grafting amine onto the ND surface was confirmed by X-ray phase analysis and IR spectroscopy. The results show a significant decrease in the average size of ND particles, from 400 nm for the pristine ones to 35 nm, and the contact angle, from 27° to 22°, with an increase in the specific surface area after treatment with a 5% solution of aminoacetic acid. Reducing the average size of NDs allows them to be better distributed throughout the epoxy matrix, which, as a result of the formation of chemical interaction at the matrix-nanofiller phase interface, can significantly increase the strength of the obtained composite. The addition of NDs treated with aminoacetic acid ensures an increase in the deformation-strength properties of epoxy composites by 19-23% relative to an epoxy composite containing the pristine NDs. Moreover, the presence of functionalized NDs significantly influences the structure and thermal stability of the epoxy nanocomposite.

Experimental studies of the deformation characteristics of mudstones under high temperature exposure

The article presents the results of laboratory thermomechanical tests of argillite samples. It has been confirmed that the deformation-strength properties of the studied type of geomaterials undergo significant changes under high-temperature influences. Features of changes in the values of deformations of argillite samples at various stages of heating were revealed. It is shown that the research results can be used in modeling thermomechanical processes occurring during underground gasification of coal in a reaction channel, to predict the development of deformation of the host rocks of an underground gas generator.

Selective destruction in alkali solutions of imide and urethane blocks in thermolized samples of copoly(urethane-imide) films

The selective destruction of urethane and imide units in a copoly(urethane-imide) obtained on the basis of pyromellitic anhydride, 4,4′-oxydianiline, toluene-2,4-diisocyanate, polycaprolactone and containing an increased proportion of imide units was investigated. A sequential destruction was carried out, including preliminary thermolysis of the samples followed by hydrolysis of the film in solutions of potassium oxide hydrate. It is shown that in the process of chemodestruction, imide units are more labile compared to urethane units (based on polycaprolactone). As a result of chemodestruction, in the final samples, which are similar in chemical structure to poly(oxydiphenylene)pyromellitimide, urethane blocks remain in residual quantities. The characterization of the final films was carried out using the methods of TGA, DSC, DMA, AFM. The deformation-strength properties of the samples remain almost constant during the destruction processes of the copoly(urethane-imide). The results obtained are of interest in the light of the development of porous membrane materials.

Effect of Negative Temperatures on the Strength and Deformability of a Reinforced Concrete Element

One of the main components of the economic development of the Russian Federation is the current trend in the development of the territories of the Far North and the Arctic. The need for such development is enshrined at the state level in various programs. Experiments on the study of the effect of negative temperatures on the operation of reinforcing steel show that with decreasing temperature, an increase in strength and modulus of elasticity is observed. At the same time, there are no unified recommendations on the deformation and strength properties of reinforcement for calculating reinforced concrete structures under conditions of low and ultra-low negative temperatures. RF standards do not take into account the influence of climatic (up to -70°C) and technological (up to -196°C) negative temperatures on the deformation and strength characteristics of reinforcing steel.The purpose of this work was to experimentally study the effect of negative temperatures (up to -196°C) on the deformation-strength properties of reinforcement, concrete and reinforced concrete rod elements. Concrete prisms 10x10x40 cm, samples of reinforcement of a periodic profile of class A400 and reinforced concrete prismatic rods with a section size of 12x18 cm and a reinforcement percentage of 1.45% were taken as prototypes. At the same time, the negative temperature of the tests varied. As a result of the studies carried out with centrally stretched reinforced concrete elements, it was found that lowering the temperature to -165°С leads to an in-crease in the cracking force by 162%; strength by 85%. Empirical dependencies are proposed to determine the deformation-strength characteristics of reinforcing steel, depending on the negative temperature.

Study of Grouting in the Hydraulically Activated Subfoundation Soils Using the Comprehensive Approach

Introduction. The large-scale “wet” closure of collieries had led to irreversible changes in the underworked rock mass. First of all, there took place the mine-water level rise and hydraulic activation of buildings’ subfoundation soils, which induced the new geodynamic effects and hazardous deformations of buildings. Therefore, it is necessary to carry out the reconstruction of buildings’ subfoundations on the underworked territories. Under these circumstances, the high-pressure jet grouting with viscoplastic grouts using the hydraulic fracturing is considered a highly-promising trend of soil grouting. The work aims at studying the parameters of grouting and the degree of consolidation of hydraulically activated soils on the underworked territories.Materials and Methods. The research was carried out with the rock full scale specimens, taking into account their physical-mechanical and strain-strength properties. The comprehensive approach to research implied studying the geotechnical conditions and the technological parameters of rock grouting along with the quality of stabilisation and waterproofing of hydraulically activated soils.Results. In accordance with the comprehensive research methodology, at the first stage, the geotechnical and miningengineering analysis of the underworked territories were carried out and the geostructural typification of the ShakhtinskNesvetaevsky district territories was substantiated depending on the thickness of the covering deposits. At the second stage, the grout pad formation parameters at contact with the parent rocks were analytically determined. Moreover, for dispersive decompacted rocks the consistent patterns and the degree of filtration consolidation were established in the empirically-analytical way by viscoplastic grout injection. Using the computer and physical modeling method, the consistent patterns of subfoundation soils deformation before and after grouting were obtained for three geostructural types. At the third stage, the field studies of the grouting parameters and quality were carried out during the subfoundations reconstruction of two buildings in the city of Shakhty. It was proved that grouting in the hydraulically activated soils increases their strength up to 0.4 MPa and reduces subfoundations deformation by 2–2.5 times.Discussion and Conclusions. Application of the comprehensive methodology to the study of grouting in the hydraulically activated soils of the underworked territories made it possible to substantiate the process flow schemes and parameters of consolidation and waterproofing of dispersive and fractured hard rocks. Based on the analytical, computer, laboratory and field study results, the consistent patterns and the degree of variation in the deformation-strength properties of the hydraulically activated subfoundation soils after viscoplastic grouting were established.

МАТЕМАТИЧЕСКИЕ МОДЕЛИ ЗАВИСИМОСТИ СТРУКТУРНЫХ И ДЕФОРМАЦИОННО-ПРОЧНОСТНЫХ СВОЙСТВ ГИПСОДРЕВЕСНОГО КОМПОЗИТА ОТ КОМПОНЕНТНОГО СОСТАВА

The production of cement-wood composites (CWC) is difficult due to the presence of extractable substances in the wood filler, which have a negative effect on the hydration of cement, the shape and size of the resulting crystalline hydrates, and the setting time, which leads to a decrease in the strength characteristics of the CWC. Gypsum-wood composites (GWC), in contrast to CWC, are less sensitive to the effects of extractable substances, but they are characterized by low strength and deformability. In order to improve the structural and deformation-strength properties of the GWC, the article presents a mathematical modeling of the effect of the component composition on the average density, open porosity, compressive strength and modulus of elasticity of a gypsum-wood composite for the installation of partitions and enclosing structures in buildings for various purposes. Mathematical models of the dependence of GWC properties on the amount of building gypsum, urea-formaldehyde resin and wood filler from freshly cut hardwood are presented. According to Student's and Fisher's criteria, an assessment was made of the statistical significance and adequacy of the obtained mathematical models, which make it possible to determine the rational values of recipe factors in the manufacture and operation of GWC with an average density of 1250-1370 kg/m3, an open porosity of 25-36%, and a compressive strength of 25-30 MPa, modulus of elasticity 1210-1780 MPa.

Effect of organoclay additive on the physical and mechanical properties of LDPE/PBT composites

The modification of low-density polyethylene/polybutyleneterephthalate (LDPE/PBT) polymer composites with organoclay was carried out and the main physical and mechanical properties of the obtained materials were studied. It has been found that organoclay has a significant effect on the basic properties of polymer composites. It is shown that such indicators as fire resistance, melt viscosity, density, heat resistance and deformation-strength properties of composites containing organoclay differ noticeably from similar parameters of the parent material. In this case, the change in properties is due to the influence of organoclay particles on the supramolecular structure of composites LDPE/PBT.

Study of the morphology of shoe sole composites based on domestic suspension polyvinyl chloride and ethylene-vinyl acetate copolymer

The paper studies the surface morphology of the initial polymers and the mixture using a scanning electron microscope SEM - EVO MA 10 (Zeiss, Germany). The X-ray phase analysis was carried out on a Panalytical Empyrean diffractometer. It has been proven that polymer mixtures based on domestic suspension polyvinyl chloride and ethylene-vinyl acetate copolymer, obtained by the method of "thermomechanical" mixing, are two-phase systems consisting of a phase of polyvinyl chloride and an ethylene- vinyl acetate copolymer. It was concluded that suspension polyvinyl chloride is fundamental in this system, which determines the main deformation-strength properties of the mixture. In the process of mixing a certain ratio of copolymer and thermoplastic, two-phase systems are formed, that is, mechanical mixtures of technologically compatible polymers with very close values of solubility parameters are formed. It has been determined that polymer mixtures based on domestic suspension polyvinyl chloride and an ethylene-vinyl acetate copolymer, obtained by the method of "thermomechanical" mixing, are two-phase systems consisting of a phase of polyvinyl chloride and an ethylene-vinyl acetate copolymer.

Development of epoxy binders modified with heat-resistant thermoplastics to create reinforced composite materials

Binders based on a mixture of epoxy oligomers modified with polyarylsulfones with controlled deformation-strength properties have been developed. Using the stepwise curing mode, fiberglass and microplastics with increased tensile strength were obtained.

Phase structure and deformation-strength properties of mixtures of polylactic acid with flexible-chain polyesters

Polylactic acid (polylactide) is the most widely used biodegradable polymer. To eliminate its brittleness and low flexibility, various approaches to plasticization are used, in particular, compounding with more flexible polymers. The possibilities of plasticizing polylactide with polycaprolactone and polybutylene adipate/terephthalate by mixing polymers in a solution with subsequent film formation have been studied as well as the thermophysical and mechanical characteristics of the resulting film materials have been studied. The effect of plasticizer additives on the phase structure of polylactide with a decrease in its crystallinity and crystallite perfection was found. Thus, a plasticizing effect with polylactide amorphization was observed. The flexibility of the materials increased, as evidenced by the increase in the relative elongation under tensile strain of the films.

ТЕРМОСТОЙКОСТЬ ПОСАДОК ПОДШИПНИКОВ КАЧЕНИЯ, ВОССТАНОВЛЕННЫХ ЭЛАСТОМЕРНЫМИ НАНОКОМПОЗИТАМИ

The heat resistance of the polymer material for restoring bearing fits is its most important operational property. The thermal stability of nanocomposites when filling elastomers with nanoparticles varies ambiguously and depends on the type of rubber that is the basis of the elastomer. To restore bearing fits, fillers, in addition to copper nanoparticles, use aluminum nanoparticles, as well as carbon nanotubes in nanocomposites. The effect of carbon nanotubes and aluminum nanoparticles on the heat resistance of elastomers was investigated. The change in the deformation-strength properties of the F-40S elastomer and nanocomposites based on it before and after high-temperature aging was experimentally studied. Composition No. 1: F-40S elastomer – 100 mass parts, Taunit carbon nanotubes – 0.1 mass parts. Composition No. 2: F-40S elastomer – 100 mass parts, aluminum nanopowder – 0.075 mass parts. Samples were made in the form of polymer films. Thermal aging of the samples was carried out under conditions of limited oxygen access to air. The heat resistance of the nanocomposite of composition No. 1, in comparison with the F-40S not filled with elastomer, has increased. The aging coefficient of the nanocomposite in strength, in comparison with the unfilled elastomer, increased by 1.2 times, and in terms of deformation, it increased by 1.38 times. The aging coefficient of the nanocomposite composition No. 2 in strength, in comparison with the unfilled elastomer, increased by 1.17 times, and in terms of deformation, it increased by 1.2 times, which confirms the increase in its heat resistance. Experimental studies have established that the Townit-M carbon nanotubes and aluminum powder nanoparticles are inhibitors of the elastomer thermal oxidation process F-40S and therefore increase the heat resistance of nanocomposites based on it.

ОПТИМИЗАЦИЯ СОСТАВА И РЕЖИМА ТЕРМИЧЕСКОЙ ОБРАБОТКИ ЭЛАСТОМЕРНОГО НАНОКОМПОЗИТА ДЛЯ ВОССТАНОВЛЕНИЯ КОРПУСНЫХ ДЕТАЛЕЙ ТЕХНИКИ

The restoration of body parts by applying elastomeric coatings eliminates wear on the holes, increases the life of the part and bearings, and significantly reduces the cost of repairing the car. The filling of the elastomeric matrix with nanoparticles allows a significant increase in the operational properties of the material. The influence of the content of aluminum filler nanoparticles, as well as the mode of thermal treatment by convective method on the deformation-strength properties of the F-40S elastomer-based nanocomposite were investigated. The mechanical properties of the nanocomposite films were evaluated according to the method of GOST 14236-81. These are: strength, elongation and specific breaking work of films. The optimal heat treatment mode of the nanocomposite was determined during the active experiment according to the second order V2 plan. It has been found that the dependence of strength and deformation on the content of the nanoscale filler has the form of a quadratic function with an extremum in the form of a maximum. The maximum strength of 21.64 MPa and the relative deformation of 2.4 have nanocomposite samples at a fill volume of 0.02. With a further increase in the content of filler, the strength and deformation of the nanocomposite samples decrease to 19.2 MPa and 2.03, respectively. The decrease in strength can be explained by aggregation of filler nanoparticles. The optimal composition of the F-40S elastomer-based nanocomposite was determined, providing the highest mechanical properties of the material: elastomer F-40S - 100 parts by weight, aluminum nanopowder - 0.075 parts by weight. Based on the results of the multifactorial experiment, a regression model of the dependence of the specific destruction work of the nanocomposite films on the temperature and time of thermal treatment by a convective method was obtained. The optimal mode of convective heating of the elastomeric nanocomposite was determined: temperature 40.0 0S, time 3.0 hours, at which the material films have the highest specific fracture operation of 52.0 MJ/m3.

Flotator Oxal as the plasticizer for suspension PVC

Flotator Oxal, a mixture of dioxane ethers and alcohols, was studied as a plasticizer for suspension PVC in comparison with the well-known dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DOP). The rheological parameters and gelation ability of the plasticizers were determined, and the values of the storage modulus and tangent of mechanical loss angle in the glassy and rubbery states were measured by the DMA method, and the glass transition temperatures were determined. The deformation-strength properties and rigidity of polymer films were tested before and after light-thermal aging. Oxal was shown to reveal a fairly low viscosity and high gelation properties in relation to PVC. At the same time, its ability to reduce the glass transition temperature and elasticize the polymer in the glassy and rubbery state is somewhat lower than that of phthalate plasticizers. PVC samples plasticized with DBP have the highest resistance to light-thermal aging.

Optimization of values of technological parameters for obtaining thermoplastic polymer composition for bottom shoes

This work reveals the dependence of the composition and production parameters on the properties of a thermoplastic polymer composition based on a copolymer of ethylene with vinyl acetate and suspension polyvinyl chloride (EVA / PVC-S), as well as the choice of the optimal composition of the mixture and finding the optimal technological parameters for its production. Thermoplastic polymer-sole compositions were obtained by the method of thermomechanical mixing. To describe the properties of polymer - plantar compositions, depending on the ratio of components and technological parameters of obtaining, the method of mathematical planning – “Full factorial experiment” of type № = 2k was chosen, which allows to obtain separate estimates of linear effects and two-, three-factor interactions. In this work, to build a mathematical model, the following factors were selected: the content of EVA in the composition, the temperature and mixing rate, and regression equations were used when obtaining a new type of shoe bottom material using a full factorial experimental method. Optimal results were obtained when the EVA content of the polymer composition was 15%, the mixing temperature was 185°C, and the mixing speed was 25 rpm. The strength and operational-technological indicators of the quality of a thermoplastic polymer composition for the bottom of footwear based on a copolymer of ethylene with vinyl acetate and suspension polyvinyl chloride have been determined. Regression equations for the dependence of the deformation-strength properties on the technological factors of the creation of polymer sole compositions are constructed. It has been proved that by selecting the optimal values of technological parameters it is possible to obtain a sole material with high deformation-strength and operational-technological characteristics.

Effect of a Deposited Silver Film on the Deformation Strength Properties of Track Membranes

Effect of a Deposited Silver Film on the Deformation Strength Properties of Track Membranes

Changes in physical and mechanical properties of soils due to anthropogenic impact on the territory of Chita

When constructing buildings and engineering structures it is necessary to make a pit for the foundation construction. Excavation works, construction of buildings and engineering structures change the deformation-strength properties of soils, which lie under the foundations. To study the changes in engineering-geological conditions during 2016-2018, on one of the construction sites in Chita (Russia), a well was made to take a soil sample and laboratory studies on physical and mechanical properties of soils were performed. As a result of the studies, it was established that the deterioration of the soils’ deformation characteristics under the foundations increased by 2.5 times, from 20 MPa to 8 MPa. The strength characteristics changed almost by 2 times. The soil’s specific cohesion changed from 31 MPa to 16 MPa due to freezing and thawing of the soil on the excavation face of the pit with its subsequent soaking. It is necessary to carry out additional activities to strengthen and stabilize the foundations.

Композиты графен-полиэтилен высокого давления и их свойства

A method for the introduction graphene into high-pressure polyethylene (HPPE) has been developed. Samples of graphene-HPPE were obtained with the content of graphene filler: 0.25%; 0.5%; 1.0%; 1.5%; 3.0%; 5.0% wt. The structural, morphological and deformation-strength properties of the obtained samples have been investigated. It was established that the increase of the elastic modulus value for the samples with the filler concentration of 3% wt and more.

BASALT AND WOLLASTONITE AS FILLERS OF THE POLYMER MATRIX

The objects of research are mineral fillers mined in the Kyrgyz Republic. The change in the deformation-strength properties of composites based on divinylstyrene thermoplastic elastomer on the amount of fillers of the polymer matrix has been investigated. Basalt and wollastonite were used as fillers in the composition of the composite material.

Development and Analysis of the Physicochemical and Mechanical Properties of Diorite-Reinforced Epoxy Composites.

The aim of this paper is to study the effect of a polyfunctional modifier oligo (resorcinol phenyl phosphate) with terminal phenyl groups and a dispersed mineral filler, diorite, on the physicochemical and deformation-strength properties of epoxy-based composites. The efficiency of using diorite as an active filler of an epoxy polymer, ensuring an increase in strength and a change in the physicochemical properties of epoxy composites, has been proven. We selected the optimal content of diorite both as a structuring additive and as a filler in the composition of the epoxy composite (0.1 and 50 parts by mass), at which diorite reinforces the epoxy composite. It has been found that the addition of diorite into the epoxy composite results in an increase in the Vicat heat resistance from 132 to 140–188 °C and increases the thermal stability of the epoxy composite, which is observed in a shift of the initial destruction temperature to higher temperatures. Furthermore, during the thermal destruction of the composite, the yield of carbonized structures increases (from 54 to 70–77% of the mass), preventing the release of volatile pyrolysis products into the gas phase, which leads to a decrease in the flammability of the epoxy composite. The efficiency of the functionalization of the diorite surface with APTES has been proven, which ensures chemical interaction at the polymer matrix/filler interface and also prevents the aggregation of diorite particles, which, in general, provides an increase in the strength characteristics of epoxy-based composite materials by 10–48%.