scholarly journals Effect of Surface Treatment of Halloysite Nanotubes (HNTs) on the Kinetics of Epoxy Resin Cure with Amines

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 930 ◽  
Author(s):  
Vahideh Akbari ◽  
Maryam Jouyandeh ◽  
Seyed Mohammad Reza Paran ◽  
Mohammad Reza Ganjali ◽  
Hossein Abdollahi ◽  
...  
Keyword(s):  
Activation Energy ◽  
Epoxy Resin ◽  
Low Cost ◽  
Halloysite Nanotubes ◽  
Diffusion Control ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Epoxy Amine ◽  
Amine System ◽  
Kinetics Of

The epoxy/clay nanocomposites have been extensively considered over years because of their low cost and excellent performance. Halloysite nanotubes (HNTs) are unique 1D natural nanofillers with a hollow tubular shape and high aspect ratio. To tackle poor dispersion of the pristine halloysite (P-HNT) in the epoxy matrix, alkali surface-treated HNT (A-HNT) and epoxy silane functionalized HNT (F-HNT) were developed and cured with epoxy resin. Nonisothermal differential scanning calorimetry (DSC) analyses were performed on epoxy nanocomposites containing 0.1 wt.% of P-HNT, A-HNT, and F-HNT. Quantitative analysis of the cure kinetics of epoxy/amine system made by isoconversional Kissinger–Akahira–Sunose (KAS) and Friedman methods made possible calculation of the activation energy (Eα) as a function of conversion (α). The activation energy gradually increased by increasing α due to the diffusion-control mechanism. However, the average value of Eα for nanocomposites was lower comparably, suggesting autocatalytic curing mechanism. Detailed assessment revealed that autocatalytic reaction degree, m increased at low heating rate from 0.107 for neat epoxy/amine system to 0.908 and 0.24 for epoxy/P-HNT and epoxy/A-HNT nanocomposites, respectively, whereas epoxy/F-HNT system had m value of 0.072 as a signature of dominance of non-catalytic reactions. At high heating rates, a similar behavior but not that significant was observed due to the accelerated gelation in the system. In fact, by the introduction of nanotubes the mobility of curing moieties decreased resulting in some deviation of experimental cure rate values from the predicted values obtained using KAS and Friedman methods.

Investigating the relationship between tack and degree of conversion in DGEBA-based epoxy resin cured with dicyandiamide and diuron

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ali Kuliaei ◽  
Iraj Amiri Amraei ◽  
Seyed Rasoul Mousavi
Keyword(s):  
Epoxy Resin ◽  
Reaction Order ◽  
Theoretical Data ◽  
Cure Kinetics ◽  
Diglycidyl Ether ◽  
Degree Of Conversion ◽  
Ozawa Method ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Kinetics Of

Abstract The purpose behind this research was to determine the optimum formulation and investigate the cure kinetics of a diglycidyl ether of bisphenol-A (DGEBA)-based epoxy resin cured by dicyandiamide and diuron for use in prepregs. First, all formulations were examined by the tensile test, and then, the specimens with higher mechanical properties were further investigated by viscometry and tack tests. The cure kinetics of the best formulation (based on tack test) in nonisothermal mode was investigated using differential scanning calorimetry at different heating rates. Kissinger and Ozawa method was used for determining the kinetic parameters of the curing process. The activation energy obtained by this method was 71.43 kJ/mol. The heating rate had no significant effect on the reaction order and the total reaction order was approximately constant ( m + n ≅ 2.1 $m+n\cong 2.1$ ). By comparing the experimental data and the theoretical data obtained by Kissinger and Ozawa method, a good agreement was seen between them. By increasing the degree of conversion, the viscosity decreased; as the degree of conversion increased, so did the slope of viscosity. The results of the tack test also indicated that the highest tack could be obtained with 25% progress of curing.

scholarly journals Non-Isothermal Sublimation Kinetics of 2,4,6-Trinitrotoluene (TNT) Nanofilms

Molecules ◽  
2019 ◽  
Vol 24 (6) ◽  
pp. 1163 ◽  
Author(s):  
Walid Hikal ◽  
Brandon Weeks
Keyword(s):  
Activation Energy ◽  
Analytical Techniques ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Absorbance Spectroscopy ◽  
Calculated Activation Energy ◽  
Sublimation Kinetics ◽  
Sublimation Rates ◽  
First Time ◽  
Kinetics Of

Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for 2,4,6-trinitrotoluene (TNT) continuous nanofilms in air using rising-temperature UV-Vis absorbance spectroscopy at different heating rates. The TNT films were prepared by the spin coating deposition technique. For the first time, the most widely used procedure to determine sublimation rates using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) was followed in this work using UV-Vis absorbance spectroscopy. The sublimation kinetics were analyzed using three well-established calculating techniques. The non-isothermal based activation energy values using the Ozawa, Flynn–Wall, and Kissinger models were 105.9 ± 1.4 kJ mol−1, 102.1 ± 2.7 kJ mol−1, and 105.8 ± 1.6 kJ mol−1, respectively. The calculated activation energy agreed well with our previously reported isothermally-measured value for TNT nanofilms using UV-Vis absorbance spectroscopy. The results show that the well-established non-isothermal analytical techniques can be successfully applied at a nanoscale to determine sublimation kinetics using absorbance spectroscopy.

scholarly journals Thermal Analysis On The Kinetics Of Magnesium-Aluminum Layered Double Hydroxides In Different Heating Rates

2015 ◽  
Vol 60 (2) ◽  
pp. 1357-1359 ◽  
Author(s):  
Y. Hongbo ◽  
C. Meiling ◽  
W. Xu ◽  
G. Hong
Keyword(s):  
Activation Energy ◽  
Thermal Analysis ◽  
Layered Double Hydroxides ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Exponential Factor ◽  
Thermal Kinetic Parameters ◽  
Double Hydroxides ◽  
Kinetics Of ◽  
Dsc Curves

Abstract The thermal decomposition of magnesium-aluminum layered double hydroxides (LDHs) was investigated by thermogravimetry analysis and differential scanning calorimetry (DSC) methods in argon environment. The influence of heating rates (including 2.5, 5, 10, 15 and 20K/min) on the thermal behavior of LDHs was revealed. By the methods of Kissinger and Flynn-Wall-Ozawa, the thermal kinetic parameters of activation energy and pre-exponential factor for the exothermic processes under non-isothermal conditions were calculated using the analysis of corresponding DSC curves.

scholarly journals Thermogravimetric Study of the Kinetics of the Reaction C + CO2 under Pore-Diffusion Control

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1886
Author(s):  
Igor Donskoy ◽  
Aleksandr Kozlov
Keyword(s):  
Activation Energy ◽  
Heterogeneous Reaction ◽  
Experimental Studies ◽  
Pore Diffusion ◽  
Diffusion Control ◽  
Diffusion Resistance ◽  
Problem Solution ◽  
Heating Rates ◽  
Carbon Gasification ◽  
Kinetics Of

This study presents experimental studies of charcoal gasification with CO2 at different heating rates (1, 5, 10, 20, and 50 K min−1). The kinetics of the reaction C + CO2 under pore-diffusion control is studied. We propose a new method for the proper determination of activation energy during the processing of thermogravimetric curves of porous carbon gasification under conditions of pore-diffusion resistance. The results of the inverse kinetic problem solution are compared with different hypotheses about the regime of the investigated heterogeneous reaction process (kinetic, diffusion, pore-diffusion). The change of reaction regimes from kinetic to diffusion is detected during charcoal gasification at different heating rates. At heating rates of 5–20 K min−1, the values of activation energy of carbon gasification reaction in the carbon dioxide atmosphere, obtained by the proposed method, closely match the data found in the previous studies. The use of diffusion models in the processing of thermogravimetric curves determines the conditions under which conventional kinetic models fail to provide adequate information about the temperature dependence of the heterogeneous reaction rate.

Crystallization Kinetics in Cu64.5Zr35.5 Binary Metallic Glass

2017 ◽  
Vol 727 ◽  
pp. 233-238 ◽  
Author(s):  
Qian Gao ◽  
Zeng Yun Jian ◽  
Jun Feng Xu ◽  
Man Zhu
Keyword(s):  
Activation Energy ◽  
Grain Growth ◽  
Crystallization Kinetics ◽  
Crystallization Process ◽  
Crystallization Kinetic ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Growth Activation ◽  
Local Activation Energy ◽  
Kinetics Of

The crystallization kinetics of melt-spun Cu64.5Zr35.5 amorphous alloy ribbons was investigated using differential scanning calorimetry (DSC) at different heating rates. Besides, the Kissinger and isoconversional approaches were used to obtain the crystallization kinetic parameters. As shown in the results, the activation energies for glass transition and crystallization process at the onset, peak and end crystallization temperatures were obtained by means of Kissinger equation to be 577.65 ± 34, 539.86 ± 54, 518.25 ± 20 and 224.84 ± 2 kJ/mol, respectively. The nucleation activation energy Enucleation is greater than grain growth activation energy Egrowth, indicating that the nucleation process is harder than grain growth. The local activation energy Eα decreases in the whole crystallization process, which suggests that crystallization process is increasingly easy.

Curing Kinetics of Silicone Epoxy Resin Containing Fluorene

2014 ◽  
Vol 936 ◽  
pp. 28-33 ◽  
Author(s):  
Wei Xing Deng ◽  
Yuan Wei Zhong ◽  
Jie Qin ◽  
Xue Bing Huang ◽  
Jin Wen Peng
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Ftir Spectroscopy ◽  
Epoxy Resin ◽  
1H Nmr ◽  
Chemical Structure ◽  
Curing Kinetics ◽  
Curing Agent ◽  
Scanning Calorimetry ◽  
Kinetics Of

A new epoxy resin based on dichlorosilane and 9,9-bis (4-hydroxyphenyl) fluorene was synthesized to produce a highly heat-resistant network. The chemical structure was characterized with FTIR spectroscopy and 1H-NMR. 4-4′-Diaminodiphenylsulfone (DDS) was used as the curing agent. The curing kinetics of different epoxy/DDS systems were investigated using non-isothermal differential scanning calorimetry (DSC). The results showed that the values of activation energy (E) were affected by the chemical structure of epoxy resin, and BPEBF exhibited lower curing reactivity towards DDS compared to E-51.

Estimation of Cure and Thermal Degradation Kinetics of Epoxy/Organoclay Nanocomposite

2010 ◽  
Vol 123-125 ◽  
pp. 667-670 ◽  
Author(s):  
Jae Young Lee ◽  
Bum Choul Choi ◽  
Hong Ki Lee
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Epoxy Matrix ◽  
Degradation Kinetics ◽  
Cure Kinetics ◽  
Diglycidyl Ether ◽  
Thermal Degradation Kinetics ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Kinetics Of

Polymer nanocomposite was synthesized through the intercalation and exfoliation of organoclay in an epoxy matrix. The epoxy matrix was composed of diglycidyl ether of bisphenol A (DGEBA, epoxy base resin), 4,4'-methylene dianiline (MDA, curing agent) and malononitrile (MN, chain extender) and organoclay was prepared by treating the montmorillonite with octadecyltrimethylammonium bromide (ODTMA). The intercalation of the organoclay was estimated by wide angle X-ray diffraction (WAXD) and transmission electron microscope (TEM) analyses. In order to measure the cure rate of DGEBA/MDA (30 phr)/MN (5 phr)/Organoclay (5 phr), differential scanning calorimetry (DSC) analysis were performed at the heating rates of 5, 10, 15 and 20 oC/min, and the data was interpreted by Kissinger equation. Thermal degradation kinetics of the epoxy nanocomposite was also studied by thermogravimetric analysis (TGA). The epoxy sample was decomposed in the TGA furnace at the heating rates of 5, 10, 15 and 20 oC/min with nitrogen atmosphere of 50 ml/min. The TGA data was introduced to the Ozawa equation and the degradation activation energy was calculated according to the degradation ratio. The activation energy for cure kinetics was 43.3 kJ/mol and that for thermal degradation was 171.5 kJ/mol.

scholarly journals The influence of montmorillonite content on the kinetics of curing of epoxy nanocomposites

2012 ◽  
Vol 66 (6) ◽  
pp. 863-870
Author(s):  
Mirjana Jovicic ◽  
Oskar Bera ◽  
Jelena Pavlicevic ◽  
Vesna Simendic ◽  
Radmila Radicevic
Keyword(s):  
Isoconversional Methods ◽  
Curing Process ◽  
Heating Rates ◽  
Epoxy Nanocomposites ◽  
Scanning Calorimetry ◽  
Epoxy Amine ◽  
Friedman Method ◽  
Kinetics Of ◽  
Dsc Curves ◽  
Energy Activation

In this work, the attention was paid at the investigation of montmorillonite dispersion in epoxy/amine systems due to improved final properties of the nanocomposites. The influence of different montmorillonite content on the kinetics of curing of epoxy/Jeffamine D-230 systems was followed by differential scanning calorimetry (DSC). The curing of epoxy nanocomposites was performed using dynamic regime at three different heating rates: 5, 10 and 20?C/min. Three isoconversional methods were applied: two integral (Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose methods) and one differential (Friedman method). The presence of montmorillonite (MMT) causes the beginning of curing at lower temperatures. The shape of the DSC curves has been changed by the addition of MMT, supporting the hypothesis of a change in the reaction mechanism. For hybrids with 3 and 5 wt.% of MMT, the E? dependence is very similar to those found for the reference system (epoxy/Jeffamine D-230) for the curing degree less than 60%. The hybrid with 10 wt.% of MMT has lower energy activation in regard to the referent system without montmorillonite. Greater differences are observed in the second part of the reaction, where it is known that the curing process is more controlled by diffusion (?>0.60). The Ea value increases at the end of the reaction (??1), which was observed for all systems, and is more pronounced in the presence of montmorillonite.

Global Kinetics of the Thermal Decomposition of Materials

1997 ◽  
Author(s):  
Azzedine Missoum ◽  
Ashwani K. Gupta ◽  
Jianrong Chen
Keyword(s):  
Heat Transfer ◽  
Activation Energy ◽  
Heating Rate ◽  
Decomposition Reaction ◽  
Decomposition Process ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Transfer Product ◽  
Product Evolution ◽  
Kinetics Of

Abstract Results on the thermal destruction behavior during the decomposition of cellulose under controlled conditions are presented. Thermogravimetric (TGA) and Differential Scanning Calorimetry (DSC) tests have been carried out on the celluose samples under conditions of various heating rate and surrounding gas environment. Pyrolysis times were also measured for different size particles having different moisture contents in a controlled mixing history reactor (CMHR). The global decomposition kinetics were investigated and it was found that the decomposition process is shifts to higher temperatures at higher heating rates as a result of the competing effects of heat and mass transfer, product diffusion and the reactions kinetics. The Arrhenius parameters for pyrolysis were determined using a first order decomposition reaction of the type, dm = −km dt. It was found that the activation energy, heat of pyrolysis and char yield are a strong function of the heating rate. An increase in heating rate from 5 to 60°C/min resulted in a change of activation energy from 204.19 to 138.31 kJ/mole °C. This heating rate dependence of the kinetics is discussed. The overall decomposition process of the examined materials is generally endothermic. In general, heat transfer, mass diffusion, product evolution, heating rate, temperature and environment are the parameters that control the decomposition process. It was also shown that heat transfer and mass transport have the most effects on the decomposition process.

Influences of Surface Chemistry on Dehydrogenation Kinetics of Ammonia Borane in Porous Carbon Scaffold

2010 ◽  
Vol 132 ◽  
pp. 19-28 ◽  
Author(s):  
Saghar Sepehri ◽  
Betzaida Batalla García ◽  
Qi Feng Zhang ◽  
Guo Zhong Cao
Keyword(s):  
Activation Energy ◽  
Surface Chemistry ◽  
Ammonia Borane ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Dehydrogenation Kinetics ◽  
Carbon Cryogel ◽  
Solid Form ◽  
Kinetics Of ◽  
Catalytic Effects

Ammonia borane (AB) with high gravimetric hydrogen capacity is of great interest for storing hydrogen in solid form which is an important issue in the growing field of hydrogen technology. In this work the effects of surface chemistry on dehydrogenation kinetics of carbon cryogel (CC) – ammonia borane nanocomposites have been studied. Boron-modified, nitrogen-modified, and boron-nitrogen- modified CCs were used as scaffold for AB and dehydrogenation kinetics of CC-ABs was studied by means of differential scanning calorimetry (DSC) at multiple heating rates. The results demonstrated that AB incorporated inside the mesopores of CC modified with nitrogen and boron possesses lower activation energy with enhanced kinetics of dehydrogenation due to catalytic effects as compared to AB in unmodified CC under otherwise the same or similar conditions. In addition, the lowest activation energy was observed for boron-modified CC-AB that could be attributed to the destabilization of AB by surface interactions with B2O3 that may accelerate the dehydrogenation process.

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