scholarly journals Modeling and experimental study of polyurethane foaming and gelling reactions

2018 ◽  
Author(s):  
◽  
Luay Jaf
Keyword(s):  
Experimental Data ◽  
Foam Height ◽  
Research Process ◽  
Catalytic Reactions ◽  
Polymerization Process ◽  
Gel Point ◽  
Reaction Proceeds ◽  
Polyurethane Foaming ◽  
Kinetics Of ◽  
Insight Into

Numerous reactions take place within a polyurethane polymerization process. Homogeneous and catalytic reactions occur at the same time and intermediate compounds are formed. As the reaction proceeds, long chains of polymer are formed which drastically affect the kinetics of the reaction. Temperature and viscosity profiles of the reacting mixture are two strong indicators of the extent of reaction and the way the reactions are carried out. Therefore, simulating polyurethane gel and foam systems helps interpret temperature and viscosity profiles and gain insight into the kinetics of the system. Using MATLAB program, a model was introduced which simultaneously solves over 80 ordinary differential equations and provide temperature and viscosity profiles as well as concentration profiles, degrees of polymerization, gel point and foam height for individual formulations. Experimental data were used to validate the code showing the model is fundamentally correct. Simulation results showed good fits to the experimental data providing reaction kinetics of the system. The model was modified to simulate reaction systems with minimal change in kinetic parameters. Finally, the simulation studies of this research provide fundamental insights into mechanism of homogenous and catalytic reactions. This research process places high demands on identifying and testing highly-impacting fundamental mechanism during polymerization that have not previously been identified.

Simulation aided analysis of polyurethane reaction systems

2015 ◽  
Author(s):  
◽  
Rima Ghoreishi
Keyword(s):  
Experimental Data ◽  
Foam Height ◽  
Polymerization Process ◽  
Gel Point ◽  
University Of Missouri ◽  
Reaction Systems ◽  
Reaction Proceeds ◽  
The University ◽  
Kinetics Of ◽  
Insight Into

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Numerous reactions take place within a polyurethane polymerization process. Homogeneous and catalytic reactions occur at the same time and intermediate compounds are formed. As the reaction proceeds, long chains of polymer are formed which drastically affect the kinetics of the reaction. Temperature and viscosity profiles of the reacting mixture are two strong indicators of the extent of reaction and the way the reactions are carried out. Therefore, simulating polyurethane gel and foam systems helps interpret temperature and viscosity profiles and gain insight into the kinetics of the system. Using MATLAB program, a model was introduced which simultaneously solves over 80 ordinary differential equations and provide temperature and viscosity profiles as well as concentration profiles, degrees of polymerization, gel point and foam height for individual formulations. Experimental data was used to validate the code showing the model is fundamentally correct. Simulation results showed good fits to the experimental data providing reaction kinetics of the system. The model was modified to simulate reaction systems with minimal change in kinetic parameters. The model successfully simulates polyurethane polymerization process for both bio-based and petroleum-based polyols. A different version of the code also simulates the formation of bio-based polyols from epoxidized soybean oil.

Density Functional Theory in Surface Science and Heterogeneous Catalysis

MRS Bulletin ◽  
2006 ◽  
Vol 31 (9) ◽  
pp. 669-674 ◽  
Author(s):  
J.K. Nørskov ◽  
M. Scheffler ◽  
H. Toulhoat
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Heterogeneous Catalysis ◽  
Surface Science ◽  
Density Functional ◽  
Catalytic Reactions ◽  
Solid Surfaces ◽  
Atomic Scale ◽  
Functional Theory ◽  
Insight Into

AbstractSolid surfaces are used extensively as catalysts throughout the chemical industry, in the energy sector, and in environmental protection. Recently, density functional theory has started providing new insight into the atomic-scale mechanisms of heterogeneous catalysis, helping to interpret the large amount of experimental data gathered during the last decades. This article shows how density functional theory can be used to describe the state of the surface during reactions and the rate of catalytic reactions. It will also show how we are beginning to understand the variation in catalytic activity from one transition metal to the next. Finally, the prospects of using calculations to guide the development of new catalysts in industry will be discussed.

Cementation kinetics of copper on a rotating zinc cylinder

1987 ◽  
Vol 52 (5) ◽  
pp. 1204-1210 ◽  
Author(s):  
Vladimír Glaser ◽  
Jan Vídenský ◽  
Miroslav Kužela
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Kinetic Equation ◽  
Rate Equation ◽  
Diffusion Region ◽  
First Order ◽  
Proportionality Constant ◽  
Zinc Surface ◽  
Reaction Proceeds ◽  
Kinetics Of

The authors followed the course of cementation of copper from sulphate solutions on a rotating zinc cylinder. Treatment of experimental data revealed that the coefficient of proportionality in the kinetic equation is not influenced by the Cu layer deposited on the zinc surface and is independent of the concentration of Cu(II) ions, but decreases with increasing concentration of ZnSO4 in solution. The cementation reaction proceeds in the diffusion region and is of the first order with respect to the concentration of Cu(II) ions; the proportionality constant in the rate equation corresponds to the mass transfer coefficient.

Influence of the Catalyst Preparation on Properties of Chromium-Magnesium Catalysts for Freon 125 Synthesis

2015 ◽  
Vol 670 ◽  
pp. 152-155
Author(s):  
Aleksandr Zirka ◽  
Ludmila Simonova ◽  
Natalia Kosova ◽  
Irina Kurzina ◽  
Sergey Reshetnikov
Keyword(s):  
Experimental Data ◽  
Gas Phase ◽  
Pore Diameter ◽  
Active Catalyst ◽  
Total Pore Volume ◽  
Catalyst Preparation ◽  
Catalytic Reactions ◽  
Bet Surface Area ◽  
Kinetics Of ◽  
Preparation Techniques

The effect of the chromium-magnesium precursor preparation techniques on physicochemical properties (BET surface area, total pore volume, mean pore diameter) and catalysts activity in the gas-phase hydrofluorination of perchloroethylene to pentafluoroethane (Freon 125) was studied. Kinetics of the catalytic reactions was studied for the most active catalyst. Based on the experimental data, the pathway of perchloroethylene fluorination with HF was suggested.

A fuzzy neural network approach for modeling the growth kinetics of FeB and Fe2B layers during the boronizing process

2018 ◽  
Vol 106 (6) ◽  
pp. 603 ◽  
Author(s):  
Bendaoud Mebarek ◽  
Mourad Keddam
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Fuzzy Neural Network ◽  
Treatment Time ◽  
Calculation Model ◽  
Average Error ◽  
Network Approach ◽  
Neural Network Approach ◽  
Fuzzy Neural ◽  
Kinetics Of

In this paper, we develop a boronizing process simulation model based on fuzzy neural network (FNN) approach for estimating the thickness of the FeB and Fe2B layers. The model represents a synthesis of two artificial intelligence techniques; the fuzzy logic and the neural network. Characteristics of the fuzzy neural network approach for the modelling of boronizing process are presented in this study. In order to validate the results of our calculation model, we have used the learning base of experimental data of the powder-pack boronizing of Fe-15Cr alloy in the temperature range from 800 to 1050 °C and for a treatment time ranging from 0.5 to 12 h. The obtained results show that it is possible to estimate the influence of different process parameters. Comparing the results obtained by the artificial neural network to experimental data, the average error generated from the fuzzy neural network was 3% for the FeB layer and 3.5% for the Fe2B layer. The results obtained from the fuzzy neural network approach are in agreement with the experimental data. Finally, the utilization of fuzzy neural network approach is well adapted for the boronizing kinetics of Fe-15Cr alloy.

Features of the kinetics of cyclic elastoplastic deformation diagrams at dwells in cycles and superimposition of variable stresses on them

2020 ◽  
Vol 86 (12) ◽  
pp. 46-53
Author(s):  
M. M. Gadenin
Keyword(s):  
Experimental Data ◽  
Elastoplastic Deformation ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Loading Cycle ◽  
Additional Variable ◽  
Dynamic Creep ◽  
Variable Stresses ◽  
Kinetics Of ◽  
Deformation Diagrams

The goal of the study is determination of the regularities of changes in cyclic strains and related deformation diagrams attributed to the existence of time dwells in the loading modes and imposition of additional variable stresses on them. Analysis of the obtained experimental data on the kinetics of cyclic elastoplastic deformation diagrams and their parameters revealed that in contrast to regular cyclic loading (equal in stresses), additional deformations of static and dynamic creep are developed. The results of the studys are especially relevant for assessing the cyclic strength of unique extremely loaded objects of technology, including nuclear power equipment, units of aviation and space systems, etc. The experiments were carried out on the samples of austenitic stainless steel under low-cycle loading and high temperatures of testing. Static and dynamic creep deformations arising under those loading conditions promote an increase in the range of cyclic plastic strain in each loading cycle and also stimulate an increase in the range of elastoplastic strain due to active cyclic deformation. At the same time the existence of dwells on extrema of stresses in cycles without imposition of additional variable stresses on them most strongly affects the growth of plastic strain ranges in cycles. Imposition of additional variable stresses on dwells also results in the development of creep strains, but their growth turns out to be somewhat less than in the presence of dwells without stresses imposed. The diagrams of cyclic deformation obtained in the experiments are approximated by power dependences, their kinetics being described in terms of the number of loading cycles using corresponding temperature-time functions. At the same time, it is shown that increase in the cyclic plastic deformation for cycles with dwells and imposition of additional variable stresses on them decreases low cycle fatigue life compared to regular loading without dwells at the same stress amplitudes, moreover, the higher the values of static and dynamic creep, the greater decrease in low-cycle fatigue life. This conclusion results from experimental data and analysis of conditions of damage accumulation for the considered forms of the loading cycle using the deformation criterion of reaching the limit state leading to fracture.

Kinetics of oxidation of ammonia on cobalt catalyst I model of the reactor with catalytically active wall

1982 ◽  
Vol 47 (8) ◽  
pp. 2087-2096 ◽  
Author(s):  
Bohumil Bernauer ◽  
Antonín Šimeček ◽  
Jan Vosolsobě
Keyword(s):  
Parabolic Equations ◽  
Cobalt Catalyst ◽  
Nonlinear Parabolic Equations ◽  
Catalytic Reactions ◽  
Temperature Profiles ◽  
Dimensional Model ◽  
Kinetics Of Oxidation ◽  
Nonlinear Parabolic ◽  
Catalytically Active ◽  
Kinetics Of

A two dimensional model of a tabular reactor with the catalytically active wall has been proposed in which several exothermic catalytic reactions take place. The derived dimensionless equations enable evaluation of concentration and temperature profiles on the surface of the active component. The resulting nonlinear parabolic equations have been solved by the method of orthogonal collocations.

Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst

1982 ◽  
Vol 47 (7) ◽  
pp. 1780-1786 ◽  
Author(s):  
Rostislav Kudláček ◽  
Jan Lokoč
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Liquid Phase ◽  
Ionizing Radiation ◽  
Oxide Catalyst ◽  
Absorbed Dose ◽  
Hydrogenation Rate ◽  
Solution Composition ◽  
Mixed Catalyst ◽  
Kinetics Of

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.

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