influence of specific intermolecular interactions on the thermal and dielectric properties of bulk polymers atomistic molecular dynamics simulations of nylon 6

Specific intermolecular interactions, in particular H-bonding, have a strong influence on the structural, thermal and relaxation characteristics of polymers. We report here the results of molecular dynamics simulations of Nylon 6 which provides an excellent example for the investigation of such an influence. To demonstrate the effect of proper accounting for H-bonding on bulk polymer properties, the AMBER99sb force field is used with two different parametrization approaches leading to two different sets of partial atomic charges. The simulations allowed the study of the thermal and dielectric properties in a wide range of temperatures and cooling rates. The feasibility of the use of the three methods for the estimation of the glass transition temperature not only from the temperature dependence of structural characteristics such as density, but also by using the electrostatic energy and dielectric constant is demonstrated. The values of glass transition temperatures obtained at different cooling rates are practically the same for the three methods. By proper accounting for partial charges in the simulations, a reasonable agreement between the results of our simulations and experimental data for the density, thermal expansion coefficient, static dielectric constant and activation energy of γ and β relaxations is obtained demonstrating the validity of the modeling approach reported

The algorithm diagram of combustion optimizing of a hydrocarbon fuels variable composition in thermal power plants

© 2018 Institute of Physics Publishing. All rights reserved. In modern power engineering, there is a problem of rational and efficient use of hydrocarbon fuels variable composition. The composition of the fuel can vary in time and from different sources. These changes lead to combustion optimum regime shift in thermal power plants. Previously, an algorithm of combustion optimizing of a hydrocarbon fuel variable composition in thermal power plants was developed. According to the algorithm, the fuel and air flows are regulated depending on the outlet temperature of the heat carrier. In this paper, a diagram of the implementation of this algorithm is presented

The heat effect of combustion process depending on fuel composition fluctuations

© Published under licence by IOP Publishing Ltd.This article describes effects of changes in the fuel composition on the combustion process. Assessment of effect made on example of the steam boiler analysis

Performance of Waterborne Polyurethanes in Inhibition of Gas Hydrate Formation and Corrosion: Influence of Hydrophobic Fragments

The design of new dual-function inhibitors simultaneously preventing hydrate formation and corrosion is a relevant issue for the oil and gas industry. The structure-property relationship for a promising class of hybrid inhibitors based on waterborne polyurethanes (WPU) was studied in this work. Variation of diethanolamines differing in the size and branching of N-substituents (methyl, n-butyl, and tert-butyl), as well as the amount of these groups, allowed the structure of polymer molecules to be preset during their synthesis. To assess the hydrate and corrosion inhibition efficiency of developed reagents pressurized rocking cells, electrochemistry and weight-loss techniques were used. A distinct effect of these variables altering the hydrophobicity of obtained compounds on their target properties was revealed. Polymers with increased content of diethanolamine fragments with n- or tert-butyl as N-substituent (WPU-6 and WPU-7, respectively) worked as dual-function inhibitors, showing nearly the same efficiency as commercial ones at low concentration (0.25 wt%), with the branched one (tert-butyl; WPU-7) turning out to be more effective as a corrosion inhibitor. Commercial kinetic hydrate inhibitor Luvicap 55 W and corrosion inhibitor Armohib CI-28 were taken as reference samples. Preliminary study reveals that WPU-6 and WPU-7 polyurethanes as well as Luvicap 55 W are all poorly biodegradable compounds; BODt/CODcr (ratio of Biochemical oxygen demand and Chemical oxygen demand) value is 0.234 and 0.294 for WPU-6 and WPU-7, respectively, compared to 0.251 for commercial kinetic hydrate inhibitor Luvicap 55 W. Since the obtained polyurethanes have a bifunctional effect and operate at low enough concentrations, their employment is expected to reduce both operating costs and environmental impact.publishedVersio

Welding dynamics in an atomistic model of an amorphous polymer blend with polymer-polymer interface

We consider an atomistic model of thermal welding at the polymer-polymer interface of a polyetherimide/polycarbonate blend, motivated by applications to 3D manufacturing in space. We follow diffusion of semiflexible chains at the interface and analyze strengthening of the samples as a function of the welding time tw by simulating the strain-stress and shear viscosity curves. The time scales for initial wetting, and for fast and slow diffusion, are revealed. It is shown that each component of the polymer blend has its own characteristic time of slow diffusion at the interface. Analysis of strainstress demonstrates saturation of the Young’s modulus at tw = 240 ns, while the tensile strength continues to increase. The shear viscosity is found to have a very weak dependence on the welding time for tw > 60 ns. It is shown that both strain-stress and shear viscosity curves agree with experimental data

Information-measuring system for monitoring the location of underground gas pipelines on the basis of improved acoustic resonance method

© Published under licence by IOP Publishing Ltd. Instrument established on the basis new method of detection hidden channels and gas pipelines, made of both metal and non-metallic materials. For the operation of the information-measuring complex was developed and created soft-ware and hardware. Laboratory and in-situ studies have been conducted to confirm the performance of the proposed technical solution

Information-measuring system for monitoring the location of underground gas pipelines on the basis of improved acoustic resonance method

© Published under licence by IOP Publishing Ltd. Instrument established on the basis new method of detection hidden channels and gas pipelines, made of both metal and non-metallic materials. For the operation of the information-measuring complex was developed and created soft-ware and hardware. Laboratory and in-situ studies have been conducted to confirm the performance of the proposed technical solution

Classification of time series using the Hurst exponent

© Published under licence by IOP Publishing Ltd. The Hurst exponent allows to classify time series according to the level of their stochasticity. To calculate it, the rescaled range analysis (R/S analysis) is applied. The article presents the R/S analysis algorithm. A program has been developed in the LabView programming environment. Performance check program carried out on the model signals

Acoustic-resonance method for control of the location of hidden hollow objects

© Published under licence by IOP Publishing Ltd. There are quite a number of methods for monitoring the location of buried pipelines: radio wave method, radiation method, acoustic location, resonant-acoustic profiling, infrared thermography, electromagnetic method. However, these methods have several disadvantages: they are not applicable to pipelines of non-metallic materials, and also have a weak selectivity in controlling the location of buried pipelines when many different communications pass in close proximity to the object under control. In this work, an improved acoustic-resonance method for controlling the location of hidden hollow objects has been developed and implemented as an information-measuring complex consisting of devices for exciting and receiving forced vibrations. The algorithmic and software-technical support of the processes of controlling the information-measuring complex and processing of vibroacoustic signals in the LabVIEW environment has been developed and created

The impact of monitoring the state of heating networks on their effectiveness

© Published under licence by IOP Publishing Ltd. The tasks of improving the efficiency and reliability of the operation of heat and power equipment are associated with the renewal of fixed production assets and a reduction in the cost of carrying out repair and restoration activities. The increase in the cost of repair and maintenance, spare parts, installation and emergency repair work in the context of a shortage of funds dictates the need to develop and implement new maintenance technologies. In this regard, scientific developments aimed at improving the methods and means of assessing the technical condition of thermal power equipment are relevant