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Xiaoping Yang - One of the best experts on this subject based on the ideXlab platform.
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effect of epoxy monomer structure on the curing process and thermo mechanical characteristics of tri functional epoxy Amine Systems a methodology combining atomistic molecular simulation with experimental analyses
Polymer Chemistry, 2017Co-Authors: Qingjie Zhang, Weihong Zhong, Hao Li, Siruo Yu, Xiaoping YangAbstract:The curing kinetics and thermo-mechanical characteristics of two kinds of high-performance Amine cured tri-functional epoxy resin compounds, including diglycidyl-4,5-epoxycyclohexane-1,2-dicarboxylate and N,N-diglycidyl-4-glycidyloxyaniline, were Systematically studied herein. Different to the simple bi-functional epoxy resins studied before, the increase in epoxy functionality and resultant asymmetric monomer structure made the whole curing behaviour more difficult to analyse. Nevertheless, there is an urgent demand to provide a thorough understanding of the tri-functional epoxy resin/Amine System in order to obtain the desired macro-performance. In this paper, a methodology, which combines atomistic molecular simulation with experimental research, was established to expound the effect of the asymmetric epoxy monomer structure on the reaction kinetics and ultimate performance of the tri-functional epoxy/Amine System. It can be utilized to efficiently analyse the cross-linking procedure and the microstructure–property relationships of epoxy resin with poly-functionality and asymmetric monomer structures, thereby serving as guidance to design high-performance polymer matrices for advanced composites.
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Effect of epoxy monomer structure on the curing process and thermo-mechanical characteristics of tri-functional epoxy/Amine Systems: a methodology combining atomistic molecular simulation with experimental analyses
Polymer Chemistry, 2017Co-Authors: Qingjie Zhang, Weihong Zhong, Hao Li, Siruo Yu, Xiaoping YangAbstract:The curing kinetics and thermo-mechanical characteristics of two kinds of high-performance Amine cured tri-functional epoxy resin compounds, including diglycidyl-4,5-epoxycyclohexane-1,2-dicarboxylate and N,N-diglycidyl-4-glycidyloxyaniline, were Systematically studied herein. Different to the simple bi-functional epoxy resins studied before, the increase in epoxy functionality and resultant asymmetric monomer structure made the whole curing behaviour more difficult to analyse. Nevertheless, there is an urgent demand to provide a thorough understanding of the tri-functional epoxy resin/Amine System in order to obtain the desired macro-performance. In this paper, a methodology, which combines atomistic molecular simulation with experimental research, was established to expound the effect of the asymmetric epoxy monomer structure on the reaction kinetics and ultimate performance of the tri-functional epoxy/Amine System. It can be utilized to efficiently analyse the cross-linking procedure and the microstructure–property relationships of epoxy resin with poly-functionality and asymmetric monomer structures, thereby serving as guidance to design high-performance polymer matrices for advanced composites.
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dispersion stability of functionalized mwcnt in the epoxy Amine System and its effects on mechanical and interfacial properties of carbon fiber composites
Materials & Design, 2016Co-Authors: Qingjie Zhang, Jianqiao Wu, Weihong Zhong, Guodong Zheng, Wei Fang, Xiaoping YangAbstract:Abstract There are many complex interactions between the functionalized multi-walled carbon nanotube (MWCNT) and curing agent/resin molecules, which result in the unstable and unsatisfactory enhancing effects of nanoparticles in epoxy–Amine System as a matrix of carbon fiber composites. In this paper, the surface chemical characteristics of carboxyl-functionalized MWCNT (MWCNT-COOH) and amino-functionalized MWCNT (MWCNT-NH 2 ) were analyzed. The reactivity of MWCNT-COOH and MWCNT-NH 2 in the epoxy matrix before and after adding Amine curing agent was discussed through non-isothermal DSC analyses and micro-morphology observation. The results showed the surface functional groups affected the dispersion stability of MWCNT during the mixing and curing process of the epoxy–Amine matrix. The potential chemical mechanisms behind the improved properties of epoxy resin containing MWCNT were specifically studied. The MWCNT-COOH tended to re-aggregate during the fabrication process of epoxy matrix, whereas MWCNT-NH 2 can maintain the dispersion stability due to the presence of Amine curing agents, which would ensure MWCNT-NH 2 more efficiently participated in the cross-linking reaction of epoxy resin and the interface strengthening between carbon fiber and resin matrix, and then resulting in the improved mechanical performances compared to the carbon fiber composites based on the neat epoxy and MWCNT-COOH reinforced ones.
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Dispersion stability of functionalized MWCNT in the epoxy–Amine System and its effects on mechanical and interfacial properties of carbon fiber composites
Materials & Design, 2016Co-Authors: Qingjie Zhang, Jianqiao Wu, Weihong Zhong, Guodong Zheng, Wei Fang, Xiaoping YangAbstract:Abstract There are many complex interactions between the functionalized multi-walled carbon nanotube (MWCNT) and curing agent/resin molecules, which result in the unstable and unsatisfactory enhancing effects of nanoparticles in epoxy–Amine System as a matrix of carbon fiber composites. In this paper, the surface chemical characteristics of carboxyl-functionalized MWCNT (MWCNT-COOH) and amino-functionalized MWCNT (MWCNT-NH 2 ) were analyzed. The reactivity of MWCNT-COOH and MWCNT-NH 2 in the epoxy matrix before and after adding Amine curing agent was discussed through non-isothermal DSC analyses and micro-morphology observation. The results showed the surface functional groups affected the dispersion stability of MWCNT during the mixing and curing process of the epoxy–Amine matrix. The potential chemical mechanisms behind the improved properties of epoxy resin containing MWCNT were specifically studied. The MWCNT-COOH tended to re-aggregate during the fabrication process of epoxy matrix, whereas MWCNT-NH 2 can maintain the dispersion stability due to the presence of Amine curing agents, which would ensure MWCNT-NH 2 more efficiently participated in the cross-linking reaction of epoxy resin and the interface strengthening between carbon fiber and resin matrix, and then resulting in the improved mechanical performances compared to the carbon fiber composites based on the neat epoxy and MWCNT-COOH reinforced ones.
Paitoon Tontiwachwuthikul - One of the best experts on this subject based on the ideXlab platform.
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1d nmr analysis of a quaternary mea deab co2 h2o Amine System liquid phase speciation and vapor liquid equilibria at co2 absorption and solvent regeneration conditions
Industrial & Engineering Chemistry Research, 2014Co-Authors: Abdulaziz Naami, Raphael Idem, Paitoon TontiwachwuthikulAbstract:New procedures were developed for our recently developed 1D NMR calibration method for quantitative liquid phase speciation analysis of a complex quaternary CO2 loaded blended Amine solution such as MEA–DEAB–CO2–H2O at high and low temperatures respectively representing CO2 stripping and absorption conditions. The ion speciation analyses were performed in conjunction with the corresponding vapor–liquid equilibrium (VLE) of the System to enable the estimation of possible CO2 capture performance. Accurate speciations were performed for a quaternary Amine System using four concentrations consisting of 5.0 M MEA blended with 0.5, 1.0, 1.5, and 1.25 M DEAB solutions with different CO2 loadings at 24 °C, and for the first time, at higher temperatures using only the NMR calibration method. By comparison, the NMR calibration method with the new procedures was shown to be valid and perhaps the only approach for determining ion speciation for quaternary Amine solutions at higher temperatures.
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1D NMR Analysis of a Quaternary MEA–DEAB–CO2–H2O Amine System: Liquid Phase Speciation and Vapor–Liquid Equilibria at CO2 Absorption and Solvent Regeneration Conditions
Industrial & Engineering Chemistry Research, 2014Co-Authors: Abdulaziz Naami, Raphael Idem, Paitoon TontiwachwuthikulAbstract:New procedures were developed for our recently developed 1D NMR calibration method for quantitative liquid phase speciation analysis of a complex quaternary CO2 loaded blended Amine solution such as MEA–DEAB–CO2–H2O at high and low temperatures respectively representing CO2 stripping and absorption conditions. The ion speciation analyses were performed in conjunction with the corresponding vapor–liquid equilibrium (VLE) of the System to enable the estimation of possible CO2 capture performance. Accurate speciations were performed for a quaternary Amine System using four concentrations consisting of 5.0 M MEA blended with 0.5, 1.0, 1.5, and 1.25 M DEAB solutions with different CO2 loadings at 24 °C, and for the first time, at higher temperatures using only the NMR calibration method. By comparison, the NMR calibration method with the new procedures was shown to be valid and perhaps the only approach for determining ion speciation for quaternary Amine solutions at higher temperatures.
Raphael Idem - One of the best experts on this subject based on the ideXlab platform.
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Catalyst performance and experimental validation of a rigorous desorber model for low temperature catalyst-aided desorption of CO2 in single and blended Amine solutions
Journal of environmental chemical engineering, 2017Co-Authors: Benjamin Decardi-nelson, Ananda Akachuku, Priscilla Anima Osei, Wayuta Srisang, Fatemeh Pouryousefi, Raphael IdemAbstract:Abstract In this study, experimental results of an integrated CO2 capture pilot plant utilizing blended MEA-MDEA solution and two solid acid catalysts (γ-Al2O3 and HZSM-5) in the desorber are presented, and a model developed in-house was validated against the experimental data. The model showed good agreement with the pilot plant data with an absolute average deviation (AAD) of 7.7% for CO2 production rates and could predict well the temperature profiles in the column. The model which has been previously validated against experimental data utilizing MEA and the two solid acid catalysts, was used to predict the performance (in terms of their contribution to the overall reaction rates) of the solid acid catalysts in both solvents (single and blended Amine solutions). The performance results showed that the catalysts contributed more to the process as the temperature and amount of catalyst increased with HZSM-5 yielding as high as 95% increase to the overall rate of reaction in the single Amine System. The results of the performance of the catalysts in the blended solvent were quite low compared to those of the single Amine solution. It was observed that the predicted gas phase CO2 concentration profiles in the desorber, which was not readily available experimentally, was quite high and undesired. Thus, further steps should be taken to address this problem.
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study of formation of bicarbonate ions in co2 loaded aqueous single 1dma2p and mdea tertiary Amines and blended mea 1dma2p and mea mdea Amines for low heat of regeneration
Industrial & Engineering Chemistry Research, 2016Co-Authors: Rui Zhang, Raphael Idem, Zhiwu Liang, Helei Liu, Wichitpan Rongwong, Xiao Luo, Qi YangAbstract:The formation of bicarbonate ions in an Amine solution during CO2 absorption results in lowering the heat duty for Amine solvent regeneration in the CO2 capture process because bicarbonate breakdown needs the lowest energy input to release CO2. In this study, bicarbonate formation was conducted for two mixed solvents consisting of tertiary Amines (1DMA2P (1 M) or MDEA (1 M)) blended with MEA in order to determine both formation rate and capacity of bicarbonate ions as compared to MEA alone. The Amines and concentrations used in the study were MEA (5 M), MEA–MDEA (5:1 molar ratio, 6 M total), and MEA–1DMA2P (5:1 molar ratio, 6 M total) at various CO2 loadings. The formation of bicarbonate ions was evaluated using 13C NMR technique at 293.15 K. The results show that for the single tertiary Amine System higher concentrations of bicarbonate ions were formed for MDEA than for 1DMA2P for the same CO2 loading. The results for the blended Amine Systems showed that bicarbonate ions were generated at CO2 loadings l...
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1d nmr analysis of a quaternary mea deab co2 h2o Amine System liquid phase speciation and vapor liquid equilibria at co2 absorption and solvent regeneration conditions
Industrial & Engineering Chemistry Research, 2014Co-Authors: Abdulaziz Naami, Raphael Idem, Paitoon TontiwachwuthikulAbstract:New procedures were developed for our recently developed 1D NMR calibration method for quantitative liquid phase speciation analysis of a complex quaternary CO2 loaded blended Amine solution such as MEA–DEAB–CO2–H2O at high and low temperatures respectively representing CO2 stripping and absorption conditions. The ion speciation analyses were performed in conjunction with the corresponding vapor–liquid equilibrium (VLE) of the System to enable the estimation of possible CO2 capture performance. Accurate speciations were performed for a quaternary Amine System using four concentrations consisting of 5.0 M MEA blended with 0.5, 1.0, 1.5, and 1.25 M DEAB solutions with different CO2 loadings at 24 °C, and for the first time, at higher temperatures using only the NMR calibration method. By comparison, the NMR calibration method with the new procedures was shown to be valid and perhaps the only approach for determining ion speciation for quaternary Amine solutions at higher temperatures.
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1D NMR Analysis of a Quaternary MEA–DEAB–CO2–H2O Amine System: Liquid Phase Speciation and Vapor–Liquid Equilibria at CO2 Absorption and Solvent Regeneration Conditions
Industrial & Engineering Chemistry Research, 2014Co-Authors: Abdulaziz Naami, Raphael Idem, Paitoon TontiwachwuthikulAbstract:New procedures were developed for our recently developed 1D NMR calibration method for quantitative liquid phase speciation analysis of a complex quaternary CO2 loaded blended Amine solution such as MEA–DEAB–CO2–H2O at high and low temperatures respectively representing CO2 stripping and absorption conditions. The ion speciation analyses were performed in conjunction with the corresponding vapor–liquid equilibrium (VLE) of the System to enable the estimation of possible CO2 capture performance. Accurate speciations were performed for a quaternary Amine System using four concentrations consisting of 5.0 M MEA blended with 0.5, 1.0, 1.5, and 1.25 M DEAB solutions with different CO2 loadings at 24 °C, and for the first time, at higher temperatures using only the NMR calibration method. By comparison, the NMR calibration method with the new procedures was shown to be valid and perhaps the only approach for determining ion speciation for quaternary Amine solutions at higher temperatures.
Qingjie Zhang - One of the best experts on this subject based on the ideXlab platform.
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effect of epoxy monomer structure on the curing process and thermo mechanical characteristics of tri functional epoxy Amine Systems a methodology combining atomistic molecular simulation with experimental analyses
Polymer Chemistry, 2017Co-Authors: Qingjie Zhang, Weihong Zhong, Hao Li, Siruo Yu, Xiaoping YangAbstract:The curing kinetics and thermo-mechanical characteristics of two kinds of high-performance Amine cured tri-functional epoxy resin compounds, including diglycidyl-4,5-epoxycyclohexane-1,2-dicarboxylate and N,N-diglycidyl-4-glycidyloxyaniline, were Systematically studied herein. Different to the simple bi-functional epoxy resins studied before, the increase in epoxy functionality and resultant asymmetric monomer structure made the whole curing behaviour more difficult to analyse. Nevertheless, there is an urgent demand to provide a thorough understanding of the tri-functional epoxy resin/Amine System in order to obtain the desired macro-performance. In this paper, a methodology, which combines atomistic molecular simulation with experimental research, was established to expound the effect of the asymmetric epoxy monomer structure on the reaction kinetics and ultimate performance of the tri-functional epoxy/Amine System. It can be utilized to efficiently analyse the cross-linking procedure and the microstructure–property relationships of epoxy resin with poly-functionality and asymmetric monomer structures, thereby serving as guidance to design high-performance polymer matrices for advanced composites.
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Effect of epoxy monomer structure on the curing process and thermo-mechanical characteristics of tri-functional epoxy/Amine Systems: a methodology combining atomistic molecular simulation with experimental analyses
Polymer Chemistry, 2017Co-Authors: Qingjie Zhang, Weihong Zhong, Hao Li, Siruo Yu, Xiaoping YangAbstract:The curing kinetics and thermo-mechanical characteristics of two kinds of high-performance Amine cured tri-functional epoxy resin compounds, including diglycidyl-4,5-epoxycyclohexane-1,2-dicarboxylate and N,N-diglycidyl-4-glycidyloxyaniline, were Systematically studied herein. Different to the simple bi-functional epoxy resins studied before, the increase in epoxy functionality and resultant asymmetric monomer structure made the whole curing behaviour more difficult to analyse. Nevertheless, there is an urgent demand to provide a thorough understanding of the tri-functional epoxy resin/Amine System in order to obtain the desired macro-performance. In this paper, a methodology, which combines atomistic molecular simulation with experimental research, was established to expound the effect of the asymmetric epoxy monomer structure on the reaction kinetics and ultimate performance of the tri-functional epoxy/Amine System. It can be utilized to efficiently analyse the cross-linking procedure and the microstructure–property relationships of epoxy resin with poly-functionality and asymmetric monomer structures, thereby serving as guidance to design high-performance polymer matrices for advanced composites.
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dispersion stability of functionalized mwcnt in the epoxy Amine System and its effects on mechanical and interfacial properties of carbon fiber composites
Materials & Design, 2016Co-Authors: Qingjie Zhang, Jianqiao Wu, Weihong Zhong, Guodong Zheng, Wei Fang, Xiaoping YangAbstract:Abstract There are many complex interactions between the functionalized multi-walled carbon nanotube (MWCNT) and curing agent/resin molecules, which result in the unstable and unsatisfactory enhancing effects of nanoparticles in epoxy–Amine System as a matrix of carbon fiber composites. In this paper, the surface chemical characteristics of carboxyl-functionalized MWCNT (MWCNT-COOH) and amino-functionalized MWCNT (MWCNT-NH 2 ) were analyzed. The reactivity of MWCNT-COOH and MWCNT-NH 2 in the epoxy matrix before and after adding Amine curing agent was discussed through non-isothermal DSC analyses and micro-morphology observation. The results showed the surface functional groups affected the dispersion stability of MWCNT during the mixing and curing process of the epoxy–Amine matrix. The potential chemical mechanisms behind the improved properties of epoxy resin containing MWCNT were specifically studied. The MWCNT-COOH tended to re-aggregate during the fabrication process of epoxy matrix, whereas MWCNT-NH 2 can maintain the dispersion stability due to the presence of Amine curing agents, which would ensure MWCNT-NH 2 more efficiently participated in the cross-linking reaction of epoxy resin and the interface strengthening between carbon fiber and resin matrix, and then resulting in the improved mechanical performances compared to the carbon fiber composites based on the neat epoxy and MWCNT-COOH reinforced ones.
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Dispersion stability of functionalized MWCNT in the epoxy–Amine System and its effects on mechanical and interfacial properties of carbon fiber composites
Materials & Design, 2016Co-Authors: Qingjie Zhang, Jianqiao Wu, Weihong Zhong, Guodong Zheng, Wei Fang, Xiaoping YangAbstract:Abstract There are many complex interactions between the functionalized multi-walled carbon nanotube (MWCNT) and curing agent/resin molecules, which result in the unstable and unsatisfactory enhancing effects of nanoparticles in epoxy–Amine System as a matrix of carbon fiber composites. In this paper, the surface chemical characteristics of carboxyl-functionalized MWCNT (MWCNT-COOH) and amino-functionalized MWCNT (MWCNT-NH 2 ) were analyzed. The reactivity of MWCNT-COOH and MWCNT-NH 2 in the epoxy matrix before and after adding Amine curing agent was discussed through non-isothermal DSC analyses and micro-morphology observation. The results showed the surface functional groups affected the dispersion stability of MWCNT during the mixing and curing process of the epoxy–Amine matrix. The potential chemical mechanisms behind the improved properties of epoxy resin containing MWCNT were specifically studied. The MWCNT-COOH tended to re-aggregate during the fabrication process of epoxy matrix, whereas MWCNT-NH 2 can maintain the dispersion stability due to the presence of Amine curing agents, which would ensure MWCNT-NH 2 more efficiently participated in the cross-linking reaction of epoxy resin and the interface strengthening between carbon fiber and resin matrix, and then resulting in the improved mechanical performances compared to the carbon fiber composites based on the neat epoxy and MWCNT-COOH reinforced ones.
Jean Pascal Eloundou - One of the best experts on this subject based on the ideXlab platform.
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Modeling complex permittivity of an epoxy-Amine System using simultaneous kinetic and microdielectric studies
Macromolecular Chemistry and Physics, 2002Co-Authors: Jean Pascal Eloundou, Jean Pierre Pascault, J. F. Gerard, David E. KranbuehlAbstract:A reactive epoxy-Amine System based on digly-cidyl ether of bisphenol A (DGEBA) with 4,4'-diaminodi-phenylsulfone (DDS) was studied during isothermal curing at 140°C and 160°C using simultaneous kinetic and microdieletric studies to establish simple models to describe the changes in the dipole component of the permittivity, e*, as a function of Tg and reaction advancement x(t). Having found that a simple relationship exists between the logarithm of the relaxation time τ and the glass transition temperature Tg, it is shown, that log τ follows the Di Benedetto equation's predicting dependence of Tg on reaction advancement as revisited by Pascault and Williams. Using this equation relating Tg and reaction advancement, the reaction advancement can be monitored directly by dielectric sensing of the changing value of the relaxation time. This equation has advantages over the WLF relationship, as in place of the fitting parameters C 1 and C 2 there is only one parameter, λ, and it is independently experimentally determined. The complex permittivity, e*, was fit to the Havriliak-Negami function. The unrelaxed permittivity at high frequency e u is assumed to be constant and the skewness parameter β was found to be independent on the temperature, the frequency, and the time while the width of the distribution decreased with time as characterized by α. During isothermal cure, the measurements made at different frequencies give the static permittivity e s versus curing time t. As the reaction proceeds, the disappearance of epoxy and Amine functions is responsible for a decrease in the effective moment of the dipoles, as characterized by e s , and of the diminution of the width of the distribution of relaxation times characterized by an increase in α. It is shown that the decrease in e s with cure time can also be used to monitor the extent of reaction advancement. Thus, in addition to cure monitoring measurements based on conductivity, dielectric measurements of the changes in the dipolar relaxation time, τ, and the low frequency static dipole polarization e s can be quantitatively used to monitor reaction advancement.
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dipolar relaxations in an epoxy Amine System
European Polymer Journal, 2002Co-Authors: Jean Pascal EloundouAbstract:Abstract Dipolar relaxations in a reactive epoxy–Amine System based on diglycidyl ether of bisphenol A with 4,4′-diaminodiphenylsulfone were studied with the Havriliak–Negami function. The System was cured isothermally at 140 °C using simultaneous kinetic and microdielectric studies. The relaxation time was calculated from the frequency fmax of the peak of the loss factor e′′ versus frequency f. A linear relation exists between the logarithm of the relaxation time τ and the glass transition temperature Tg. Then, logτ follows the Di Benedetto equation revisited by Pascault and Williams allowing the prediction of the relaxation time τ during cure. The unrelaxed permittivity at high frequency eu, the relaxed or static permittivity es and the skewness parameter β were found independent on the conversion or the curing time. The distribution parameter α decreases as curing time t increases. The difficulty of orientation of dipoles in the electric field due to vitrification is responsible of these behaviours.
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Dipolar relaxations in an epoxy–Amine System
European Polymer Journal, 2002Co-Authors: Jean Pascal EloundouAbstract:Abstract Dipolar relaxations in a reactive epoxy–Amine System based on diglycidyl ether of bisphenol A with 4,4′-diaminodiphenylsulfone were studied with the Havriliak–Negami function. The System was cured isothermally at 140 °C using simultaneous kinetic and microdielectric studies. The relaxation time was calculated from the frequency fmax of the peak of the loss factor e′′ versus frequency f. A linear relation exists between the logarithm of the relaxation time τ and the glass transition temperature Tg. Then, logτ follows the Di Benedetto equation revisited by Pascault and Williams allowing the prediction of the relaxation time τ during cure. The unrelaxed permittivity at high frequency eu, the relaxed or static permittivity es and the skewness parameter β were found independent on the conversion or the curing time. The distribution parameter α decreases as curing time t increases. The difficulty of orientation of dipoles in the electric field due to vitrification is responsible of these behaviours.
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Microdielectric study of epoxy‐Amine Systems: Gelation and relationships between conductivity and kinetics
Angewandte Makromolekulare Chemie, 1998Co-Authors: Jean Pascal Eloundou, Jean Pierre Pascault, Gisèle Boiteux, J. F. Gerard, Gérard SeytreAbstract:A low-Tg epoxy-Amine System, based on the diglycidyl ether of butane-1,4-diol (DGEBD) and 4,9-dioxadodecane-1,12-diAmine (4D), and a high-Tg epoxy-Amine System, based on diglycidyl ether of bisphenol A (DGEBA) and 4,4´-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA), were studied during isothermal curing by means of microdielectrometry. The first one, which was investigated from 40°C to 60°C, exhibits only a gelation phenomenon. The latter was studied from 80°C to 150°C. At these temperatures, gelation and vitrification phenomena occur. To observe gelation phenomenon from the dielectric curves, three different approaches were developed (inflexion point as gelation criterion, percolation theory, and correlation between conductivity and viscosity) which fail to describe the complete evolution of the epoxy-Amine reactive Systems during cure. This is due to the fact that at the gel point the macroscopic viscosity diverges whereas the conductivity values involve the ion motions, thus the local viscosities. So, there is no manifestation of gelation in the dielectric curves. The values of logσ/logσ0 vs. conversion x, where σ0 is the conductivity of the initial monomer mixture, give a single curve which can be fitted by a model proposed recently. In addition, a linear relation exists between log σ(x)/log σ0 and glass transition temperature, Tg(x). Thus, the combination of these relations with the modified Di Benedetto equation allows predicting kinetic and dielectric behaviors knowing the glass transition temperatures, the heat capacities, and the conductivities of the initial monomer mixture and of the fully cured network. Ein Epoxy-Amin-System mit niedriger Glasubergangstemperatur Tg auf der Basis des Diglycidylethers von Butan-1,4-diol (DGEBD) und 4,9-Dioxadodecan-1,12-diamin (4D) und ein Epoxy-Amin-System mit hoher Tg auf der Basis des Diglycidylethers von Bisphenol A (DGEBA) und 4,4´-Methylenbis(3-chlor-2,6-diethylanilin) (MCDEA) wurden wahrend der isothermen Hartung mit der Mikrodielektrometrie untersucht. Bei dem ersten System, das zwischen 40°C und 60°C gemessen wurde, wird lediglich Gelbildung beobachtet. Das zweite System wurde zwischen 80°C und 150°C untersucht, wobei sowohl Gelbildung als auch Glasbildung auftreten. Um die Gelbildung anhand der Dielektrizitatskurven zu verfolgen, wurden drei unterschiedliche Methoden herangezogen (der Inflexionspunkt als Gelbildungskriterium, die Perkolationstheorie und die Korrelation zwischen Leitfahigkeit und Viskositat), die jedoch alle bei der Beschreibung der vollstandigen Entwicklung der reaktiven Epoxy-Amin-Systeme wahrend der Hartung versagten. Die Ursache ist, das am Gelpunkt die makroskopische Viskositat divergiert, wahrend die Leitfahigkeitswerte Ionenbewegungen – also lokale Viskositaten – einbeziehen. Aus diesem Grund kann die Gelbildung nicht anhand der Dielektrizitatskurven beobachtet werden. Auftragen der log σ/log σ0-Werte (σ0 ist die Leitfahigkeit der ursprunglichen Monomermischung) gegen den Umsatz x ergibt eine Kurve, die nach einem kurzlich vorgeschlagenen Modell angepast werden kann. Auserdem besteht ein linearer Zusammenhang zwischen log σ(x)/log σ0 und der Glasubergangstemperatur Tg(x). Die Kombination dieser Beziehungen mit der modifizierten Di Benedetto-Gleichung erlaubt bei Kenntnis der Glasubergangstemperatur, der Warmekapazitat und der Leitfahigkeit der Ausgangsmonomermischung und des ausgeharteten Netzwerks Vorhersagen zum kinetischen und dielektrischen Verhalten.
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Temperature dependence of the behavior of a reactive epoxy-Amine System by means of dynamic rheology. 2. High-Tg epoxy-Amine System
Macromolecules, 1996Co-Authors: Jean Pascal Eloundou, Jean-françois Gérard, Daniel Harran, Jean Pierre PascaultAbstract:A high-Tg epoxy−Amine System based on diglycidyl ether of bisphenol A (DGEBA) and 4,4‘-methylenebis[3-chloro-2,6-diethylaniline] (MCDEA) was studied near the gel point in isothermal conditions from 80 to 180 °C by means of a rheological method, thus, below and above the glass transition temperature of the fully cured network, Tg∞ (Tg∞ = 177 °C). The lower limit of this temperature range is close to gelTg (gelTg = 50 °C), the temperature at which gelation and vitrification occur simultaneously. Close to the gel point, the power laws relating viscosity, η, to e-k and the storage shear modulus, G‘, to ez (e = |x − xgel|/xgel) are verified above 150 °C. The scaling law ∂(log G*)/∂t proportional to ω-κ is verified only at 170 °C (κ = 0.25) and 180 °C (κ = 0.18). The exponents k and Δ are constant above 150 °C (k = 1.43 ± 0.03, Δ = 0.69 ± 0.01) and are very close to those found in the Rouse percolation model. Below 150 °C, these exponents diminish as the curing temperature decreases. The exponent z is frequency...