Connection of water permeability with a number of physical properties of polymers

Currently, methods for predicting the properties of polymers are very popular, since they simplify the work of synthetic chemists. Instead of lengthy and time-consuming experiments, many properties of polymers can be predicted in advance based on their chemical structure. Naturally, such tasks must be computerized so that the properties are predicted after the chemical structure of the repeating polymer unit is displayed on the display screen. This is the so-called direct task. The inverse problem is more complex and interesting. It consists in entering the intervals of the desired characteristics into the computer. Then computer synthesis of polymers possessing these characteristics are realized. The work consists in writing a computer program that allows the computer synthesis of polymers of different classes with specified intervals of water permeability. These classes include polyurethanes, polysulfones, polysulfides, polyethers and polyesters, polyamides, polyketones and polyethyrketones, polycarbonates, polyolefins, vinyl polymers, polystyrene, acrylic and methacrylic polymers. On the basis of this program, water permeability compatibility diagrams are constructed with various physical characteristics of polymers – glass transition temperature, temperature of the onset of intensive thermal degradation, cohesion energy, density, solubility parameter (Hildebrand parameter)

Assessment of the reliability of bent reinforced concrete elements under corrosive effects

The main problem of reducing the reliability and durability of reinforced concrete structures is the corrosion of concrete and reinforcement of operated buildings and structures. Calculation of structures made of reinforced concrete, taking into account environmental influences, is complicated by the stochastic nature of the parameters of corrosion processes. The conducted studies are aimed at solving the problem of improving the methodology of the probabilistic approach to the calculation of corrosion-damaged reinforced concrete elements. The article considers a probabilistic assessment of reliability for the most common bent reinforced concrete elements, taking into account corrosive wear and the time factor. The modeling of the effect of corrosion processes on the stress-strain state of a reinforced concrete element was carried out using the concrete deformation diagram, which takes into account the decrease in strength characteristics with an increase in the concentration of an aggressive medium in concrete. The scheme of propagation of an aggressive environment in concrete is adopted according to the diffuse front method. Corrosion processes in reinforcement were taken into account by reducing the effective cross-sectional area of reinforcing bars. The change in the properties of steel (its embrittlement) with an increase in the concentration of an aggressive medium was not taken into account. Reinforcement corrosion was simulated after the incubation period, after the concentration of the aggressive medium on the surface of the reinforcing bars reached a critical value. The determination of the moment of the onset of the limit state in the element was carried out on the basis of a nonlinear deformation model at each point of the section of the element to achieve the maximum possible tensile or compression strains in concrete and reinforcement. To solve the problem of reliability assessment, the method of statistical modeling implemented in a specialized software package was used. To apply this method, according to previous studies, the probabilistic parameters of all random variables were taken: mathematical expectation and standard deviation. Based on the results of the reliability assessment, graphs of the decrease in the reliability of a bent reinforced concrete element from the time of exposure to an aggressive environment were obtained

Study of the abrasion resistance of wood-polymer composites and mixtures of ABS-plastic with polyvinyl chloride

The abrasion of materials based on blends of ABS plastic with polyvinyl chloride (PVC) as well as terraced boards based on wood-polymer composites (DPC) has been studied. The measurements were carried out on a drum-type machine, and on a Taber's abrasimeter. For blends of ABS plastic with PVC at abrasion path length 600 m wear is 0.85%. For terracotta boards based on WPC, the wear during the test (loss of mass) was 0.0042 g. The abrasion of the sample was 9.29×10-5 g/cm2. Thus, the obtained blends should be recommended for application for floor coverings, since they possess negligible abrasion

Stress-optical coefficients of copolymers

The stress-optical coefficient Cσ of copolymers based on cured epoxy resins has been calculated. Calculations were made for epoxy resins based on bisphenol A and aliphatic and aromatic diamines. The Cσ values are in the range of 91.6÷103 weight percent. All calculations were carried out using the Cascade computer program (developed by INEOS RAS). The investigated structures of cured epoxy resins are obtained from industrial components. High Cσ values make it possible to confidently use the mentioned network polymers in the photoelasticity method, from which models of full-scale building structures can be made

Newest models and calculation schemes for quantitative analysis of physical properties of polymers

New models and calculation schemes have been developed for the quantitative analysis of a number of physical properties of polymers — glass transition temperature, flow temperature of polymer nanocomposites, thermal conductivity, boiling point of polymer solutions, water absorption and water permeability of polymers and nanocomposites, strength, viscosity, storage and losses moduli, refractive index and dielectric constant. All calculation schemes are based on the structure of linear and cross-linked polymers; their degree of crystallinity, free volume, the effect of temperature, the composition of copolymers and homogeneous mixtures of polymers, the concentration of nanoparticles, their shape, size distribution, orientation angles, the structure of polar groups grafted to the surface of nanoparticles, the energy of intermolecular interactions are taken into account. All computational schemes are computerized and allow calculations to be carried out automatically after the introduction of the structure of a repeating unit of polymer unit into the computer, as well as the shape and size of nanofillers

Water absorption of wood-polymer composites of savewood

The materials based on wood-polymer composites (WPC) in the form of decking boards are produced, in which wood filler is partially replaced by mineral one. WPC materials manufactured by Savewood using a matrix polymer of polyvinyl chloride (PVC) have good mechanical properties, low abrasion and satisfactory resistance to climatic influences. However, they have relatively high water absorption, the task of reducing which is relevant not only in Russia, but also in other countries where there are constructions of facilities operating in outdoor environmental conditions. The modification of such materials in this work was carried out by replacing part of the wood filler with the mineral filler, which is CaCO3 (chalk). Partial replacement of wood flour with mineral filler resulted in a marked reduction in swelling from 1.25 to 0.01%. In this case, the modulus of elasticity is increased from 2260 to 2880 MPa, tensile strength from 30.5 to values of 16.7 ÷ 32 MPa. The specific impact strength varies from 8.90 to 7.74 kJ/m2. The optimal ratio of wood and mineral fillers is 60/40%.</jats:p

Water absorption of wood-polymer composites of savewood

The materials based on wood-polymer composites (WPC) in the form of decking boards are produced, in which wood filler is partially replaced by mineral one. WPC materials manufactured by Savewood using a matrix polymer of polyvinyl chloride (PVC) have good mechanical properties, low abrasion and satisfactory resistance to climatic influences. However, they have relatively high water absorption, the task of reducing which is relevant not only in Russia, but also in other countries where there are constructions of facilities operating in outdoor environmental conditions. The modification of such materials in this work was carried out by replacing part of the wood filler with the mineral filler, which is CaCO3 (chalk). Partial replacement of wood flour with mineral filler resulted in a marked reduction in swelling from 1.25 to 0.01%. In this case, the modulus of elasticity is increased from 2260 to 2880 MPa, tensile strength from 30.5 to values of 16.7 ÷ 32 MPa. The specific impact strength varies from 8.90 to 7.74 kJ/m2. The optimal ratio of wood and mineral fillers is 60/40%

Finite Element Analysis of the Bearing Capacity of Beamless Floor Slabs under Punching, Taking into Account the Design Parameters of the Contacting Elements

Static calculations of experimental models in an elastic formulation were carried out, and the regularities connecting the dependences of forces in the calculated cross-section of punching out from the main structural parameters of contacting elements (reinforced concrete slabs and pylons) and from the used concrete class were revealed. This article concerns the safety issues of reinforced concrete slabs under punching with different ratios and combinations of pylon and slab thickness parameters, as well as concrete strength. The objectives of the research are consideration of the fracture pattern of reinforced concrete monolithic slabs due to punching shear; comparative analysis of modern normative calculation methods and flat reinforced concrete slabs due to static punching shear; finite element modelling and analysis of the punching shear calculation results for reinforced concrete floor slabs; and the force distribution over the area of the contacting elements-saw and floor slab. The practical significance of the results lies in the use of the obtained forces in the contacting elements for the calculation and design of reliable structures of beamless floor slabs

Modeling of water permeability through the polymer nanocomposites

Abstract The influence of chemical and physical parameters of polymer nanocomposites on the water permeability is analyzed. The chemical structure of the matrix polymer and the polar groups grafted onto the surface of the nanoparticles lead to the greatest influence. A large influence is exerted by the concentration of nanoparticles, their shape and size distribution. The direction of the penetration front in the nanocomposite sample has a lesser effect.</jats:p