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.

scholarly journals Epoxy/Ionic Liquid-Modified Mica Nanocomposites: Network Formation–Network Degradation Correlation

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1990
Author(s):  
Maryam Jouyandeh ◽  
Vahideh Akbari ◽  
Seyed Mohammad Reza Paran ◽  
Sébastien Livi ◽  
Luanda Lins ◽  
...  
Keyword(s):  
Activation Energy ◽  
Network Formation ◽  
Isoconversional Methods ◽  
Epoxide Ring ◽  
Segmental Motion ◽  
Heating Rates ◽  
Epoxy Nanocomposites ◽  
Scanning Calorimetry ◽  
Amine Curing ◽  
Kinetics Of

We synthesized pristine mica (Mica) and N-octadecyl-N’-octadecyl imidazolium iodide (IM) modified mica (Mica-IM), characterized it, and applied it at 0.1–5.0 wt.% loading to prepare epoxy nanocomposites. Dynamic differential scanning calorimetry (DSC) was carried out for the analysis of the cure potential and kinetics of epoxy/Mica and epoxy/Mica-IM curing reaction with amine curing agents at low loading of 0.1 wt.% to avoid particle aggregation. The dimensionless Cure Index (CI) was used for qualitative analysis of epoxy crosslinking in the presence of Mica and Mica-IM, while qualitative cure behavior and kinetics were studied by using isoconversional methods. The results indicated that both Mica and Mica-IM improved the curability of epoxy system from a Poor to Good state when varying the heating rate in the interval of 5–15 °C min−1. The isoconversional methods suggested a lower activation energy for epoxy nanocomposites with respect to the blank epoxy; thus, Mica and Mica-IM improved crosslinking of epoxy. The higher order of autocatalytic reaction for epoxy/Mica-IM was indicative of the role of liquid crystals in the epoxide ring opening. The glass transition temperature for nanocomposites containing Mica and Mica-IM was also lower than the neat epoxy. This means that nanoparticles participated the reaction because of being reactive, which decelerated segmental motion of the epoxy chains. The kinetics of the thermal decomposition were evaluated for the neat and mica incorporated epoxy nanocomposites epoxy with varying Mica and Mica-IM amounts in the system (0.5, 2.0 and 5.0 wt.%) and heating rates. The epoxy/Mica-IM at 2.0 wt.% of nanoparticle showed the highest thermal stability, featured by the maximum value of activation energy devoted to the assigned system. The kinetics of the network formation and network degradation were correlated to demonstrate how molecular-level transformations can be viewed semi-experimentally.

scholarly journals A Comparative Study on Cure Kinetics of Layered Double Hydroxide (LDH)/Epoxy Nanocomposites

2020 ◽  
Vol 4 (3) ◽  
pp. 111
Author(s):  
Zohre Karami ◽  
Seyed Mohammad Reza Paran ◽  
Poornima Vijayan P. ◽  
Mohammad Reza Ganjali ◽  
Maryam Jouyandeh ◽  
...  
Keyword(s):  
Layered Double Hydroxide ◽  
Cure Kinetics ◽  
Frequency Factor ◽  
Isoconversional Methods ◽  
Epoxide Ring ◽  
Epoxy Nanocomposites ◽  
Scanning Calorimetry ◽  
Noncatalytic Reaction ◽  
Double Hydroxide ◽  
Kinetics Of

Layered double hydroxide (LDH) minerals are promising candidates for developing polymer nanocomposites and the exchange of intercalating anions and metal ions in the LDH structure considerably affects their ultimate properties. Despite the fact that the synthesis of various kinds of LDHs has been the subject of numerous studies, the cure kinetics of LDH-based thermoset polymer composites has rarely been investigated. Herein, binary and ternary structures, including [Mg0.75 Al0.25 (OH)2]0.25+ [(CO32−)0.25/2∙m H2O]0.25−, [Mg0.75 Al0.25 (OH)2]0.25+ [(NO3−)0.25∙m H2O]0.25− and [Mg0.64 Zn0.11 Al0.25 (OH)2]0.25+ [(CO32−)0.25/2∙m H2O]0.25−, have been incorporated into epoxy to study the cure kinetics of the resulting nanocomposites by differential scanning calorimetry (DSC). Both integral and differential isoconversional methods serve to study the non-isothermal curing reactions of epoxy nanocomposites. The effects of carbonate and nitrate ions as intercalating agents on the cure kinetics are also discussed. The activation energy of cure (Eα) was calculated based on the Friedman and Kissinger–Akahira–Sunose (KAS) methods for epoxy/LDH nanocomposites. The order of autocatalytic reaction (m) for the epoxy/Mg-Al-NO3 (0.30 and 0.254 calculated by the Friedman and KAS methods, respectively) was smaller than that of the neat epoxy, which suggested a shift of the curing mechanism from an autocatalytic to noncatalytic reaction. Moreover, a higher frequency factor for the aforementioned nanocomposite suggests that the incorporation of Mg-Al-NO3 in the epoxy composite improved the curability of the epoxy. The results elucidate that the intercalating anions and the metal constituent of LDH significantly govern the cure kinetics of epoxy by the participation of nitrate anions in the epoxide ring-opening reaction.

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 Bulk-Surface Modification of Nanoparticles for Developing Highly-Crosslinked Polymer Nanocomposites

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1820 ◽  
Author(s):  
Maryam Jouyandeh ◽  
Mohammad Reza Ganjali ◽  
Mustafa Aghazadeh ◽  
Sajjad Habibzadeh ◽  
Krzysztof Formela ◽  
...  
Keyword(s):  
Surface Modification ◽  
Polymer Nanocomposite ◽  
Isoconversional Methods ◽  
Heating Rates ◽  
Epoxy Nanocomposites ◽  
Scanning Calorimetry ◽  
Cure Reaction ◽  
Crosslinked Polymer ◽  
Diffusion Controlled ◽  
Bulk Modification

Surface modification of nanoparticles with functional molecules has become a routine method to compensate for diffusion-controlled crosslinking of thermoset polymer composites at late stages of crosslinking, while bulk modification has not carefully been discussed. In this work, a highly-crosslinked model polymer nanocomposite based on epoxy and surface-bulk functionalized magnetic nanoparticles (MNPs) was developed. MNPs were synthesized electrochemically, and then polyethylene glycol (PEG) surface-functionalized (PEG-MNPs) and PEG-functionalized cobalt-doped (Co-PEG-MNPs) particles were developed and used in nanocomposite preparation. Various analyses including field-emission scanning electron microscopy, Fourier-transform infrared spectrophotometry (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM) were employed in characterization of surface and bulk of PEG-MNPs and Co-PEG-MNPs. Epoxy nanocomposites including the aforementioned MNPs were prepared and analyzed by nonisothermal differential scanning calorimetry (DSC) to study their curing potential in epoxy/amine system. Analyses based on Cure Index revealed that incorporation of 0.1 wt.% of Co-PEG-MNPs into epoxy led to Excellent cure at all heating rates, which uncovered the assistance of bulk modification of nanoparticles to the crosslinking of model epoxy nanocomposites. Isoconversional methods revealed higher activation energy for the completely crosslinked epoxy/Co-PEG-MNPs nanocomposite compared to the neat epoxy. The kinetic model based on isoconversional methods was verified by the experimental rate of cure reaction.

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.

scholarly journals Curing kinetics of two commercial urea-formaldehyde adhesives studied by isoconversional method

2011 ◽  
Vol 65 (6) ◽  
pp. 717-726 ◽  
Author(s):  
Mladjan Popovic ◽  
Jaroslava Budinski-Simendic ◽  
Mirjana Jovicic ◽  
Joszef Mursics ◽  
Milanka Djiporovic-Momcilovic ◽  
...  
Keyword(s):  
Activation Energy ◽  
Urea Formaldehyde ◽  
Curing Kinetics ◽  
Isoconversional Methods ◽  
Isoconversional Method ◽  
Reaction Enthalpy ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Kinetics Of

Differential scanning calorimetry (DSC) was used to evaluate the curing kinetics of two commercial urea-formaldehyde (UF) adhesives having different formaldehyde to urea (F/U) ratio of 1.112 (UF1) and 1.086 (UF2). DSC measurements were done in dynamic scanning regime with heating rates of 5, 10, 15 and 20?C?min-1 in order to determine the activation energy for each adhesive. Obtained data were analyzed using isoconversional methods with application of Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose kinetic models. In addition, different catalyst levels were tested at the heating rate of 10?C/min. Results showed that the adhesive with higher F/U ratio achieved higher activation energy, while having lower peak temperature of curing reaction. It was also noticed that the increase of catalyst level influenced the increase of reaction enthalpy of the adhesive with lower F/U ratio.

Effects of additives on the cure kinetics of vinyl ester pultrusion resins

2021 ◽  
pp. 002199832110015
Author(s):  
Alexander Vedernikov ◽  
Yaroslav Nasonov ◽  
Roman Korotkov ◽  
Sergey Gusev ◽  
Iskander Akhatov ◽  
...  
Keyword(s):  
Vinyl Ester ◽  
Mean Squared Error ◽  
Cure Kinetics ◽  
Zinc Stearate ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Different Temperatures ◽  
Predicted Values ◽  
Kinetics Of ◽  
Final Degree

Pultrusion is a highly efficient composite manufacturing process. To accurately describe pultrusion, an appropriate model of resin cure kinetics is required. In this study, we investigated cure kinetics modeling of a vinyl ester pultrusion resin (Atlac 430) in the presence of aluminum hydroxide (Al(OH)3) and zinc stearate (Zn(C18H35O2)2) as processing additives. Herein, four different resin compositions were studied: neat resin composition, composition with Al(OH)3, composition comprising Zn(C18H35O2)2, and composition containing both Al(OH)3 and Zn(C18H35O2)2. To analyze each composition, we performed differential scanning calorimetry at the heating rates of 5, 7.5, and 10 K/min. To characterize the cure kinetics of Atlac 430, 16 kinetic models were tested, and their performances were compared. The model based on the [Formula: see text]th-order autocatalytic reaction demonstrated the best results, with a 4.5% mean squared error (MSE) between the experimental and predicted data. This study proposes a method to reduce the MSE resulting from the simultaneous melting of Zn(C18H35O2)2. We were able to reduce the MSE by approximately 34%. Numerical simulations conducted at different temperatures and pulling speeds demonstrated a significant influence of resin composition on the pultrusion of a flat laminate profile. Simulation results obtained for the 600 mm long die block at different die temperatures (115, 120, 125, and 130 °C) showed that for a resin with a final degree of cure exceeding 95% at the die exit, the maximum difference between the predicted values of pulling speed for a specified set of compositions may exceed 1.7 times.

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 Formation of metal oxide-based hydroxysodalite by alkali-activation of kaolinite

Chemija ◽  
2020 ◽  
Vol 31 (3) ◽  
Author(s):  
Ehab AlShamaileh ◽  
Muayad Esaifan ◽  
Qusay Abu-Afifeh
Keyword(s):  
Activation Energy ◽  
Metal Oxide ◽  
Alkali Activation ◽  
Dsc Analysis ◽  
X Ray Diffraction ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Xrd Study ◽  
Dsc Curves

The formation of metal oxide-based hydroxysodalite by alkali-activation of kaolinite is studied using X-ray diffraction (XRD) study and differential scanning calorimetry (DSC) analysis. Different metal oxides (CoO, MgO, FeO and SiO2) were used to form the metal oxide-based hydroxysodalite. The transformation from kaolinite into hydroxysodalite is confirmed by XRD. In the thermodynamic study, the maximum peak temperatures for DSC curves at various heating rates were used to determine the activation energy (Ea) of the hydroxysodalite formation. With magnesium oxide and cobalt oxide, the formation process was found to be exothermic while it was endothermic with iron oxide.

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.

Sign in / Sign up

Export Citation Format

Share Document