Isoconversional kinetic analysis of the alkyd/melamine resins curing

The curing reaction for the mixtures of alkyd resins based on ricinoleic acid, phthalic anhydride and three polyols (glycerin, trimethylolpropane or ethoxylated pentaerythritol) with two different commercial melamine resins was investigated by differential scanning calorimetry (DSC). The curing kinetics analysis was performed using the isoconversional methods (Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose and Friedman). Isoconversional methods were carried out with three heating rates (5, 10 and 20?C/min) in a scanning temperature range from 40 to 250?C. It was found that the curing activation energy of resin mixtures is influenced by alkyd and melamine resin type due to the catalytic effect of hydroxyl group on the reactions. The dependence of apparent curing degree on time, which was obtained by mathematical transformations of dynamic DSC data using Ozawa-Flynn-Wall method, describes well the isothermal DSC experiments.

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

Hemijska industrija ◽

10.2298/hemind110912088p ◽

2011 ◽

Vol 65 (6) ◽

pp. 717-726 ◽

Cited By ~ 6

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.

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

Polymers ◽

10.3390/polym12081820 ◽

2020 ◽

Vol 12 (8) ◽

pp. 1820 ◽

Cited By ~ 1

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.

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Kinetic Analysis of the Curing of a Partially Biobased Epoxy Resin Using Dynamic Differential Scanning Calorimetry

Polymers ◽

10.3390/polym11030391 ◽

2019 ◽

Vol 11 (3) ◽

pp. 391 ◽

Cited By ~ 13

Author(s):

Diego Lascano ◽

Luis Quiles-Carrillo ◽

Rafael Balart ◽

Teodomiro Boronat ◽

Nestor Montanes

Keyword(s):

Experimental Data ◽

Activation Energy ◽

Differential Scanning Calorimetry ◽

Epoxy Resins ◽

Curing Kinetics ◽

Reaction Model ◽

Diglycidyl Ether ◽

Heating Rates ◽

Scanning Calorimetry ◽

Model Free

This research presents a cure kinetics study of an epoxy system consisting of a partially bio-sourced resin based on diglycidyl ether of bisphenol A (DGEBA) with amine hardener and a biobased reactive diluent from plants representing 31 wt %. The kinetic study has been carried out using differential scanning calorimetry (DSC) under non-isothermal conditions at different heating rates. Integral and derivative isoconversional methods or model free kinetics (MFK) have been applied to the experimental data in order to evaluate the apparent activation energy, Ea, followed by the application of the appropriate reaction model. The bio-sourced system showed activation energy that is independent of the extent of conversion, with Ea values between 57 and 62 kJ·mol−1, corresponding to typical activation energies of conventional epoxy resins. The reaction model was studied by comparing the calculated y(α) and z(α) functions with standard master plot curves. A two-parameter autocatalytic kinetic model of Šesták–Berggren [SB(m,n)] was assessed as the most suitable reaction model to describe the curing kinetics of the epoxy resins studied since it showed an excellent agreement with the experimental data.

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

Hemijska industrija ◽

10.2298/hemind120814111j ◽

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.

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Curing Kinetics Analysis of Dgeba-Mda System

Advanced Composites Letters ◽

10.1177/096369359400300305 ◽

1994 ◽

Vol 3 (3) ◽

pp. 096369359400300

Author(s):

G. Carotenuto ◽

L. Nicolais

Keyword(s):

Differential Scanning Calorimetry ◽

High Performance ◽

Spectroscopic Analysis ◽

Curing Kinetics ◽

Kinetics Analysis ◽

Epoxy System ◽

Scanning Calorimetry ◽

Step Process ◽

Characterization Study ◽

High Performance Composite

Thermoset polymers and thermoset based composites are normally polymerized and performed in a step process. This work studies the kinetics behavior of a commercial epoxy system used as matrices of medium and high performance composite materials. The characterization study was performed by differential scanning calorimetry (DSC) and spectroscopic analysis.

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Kinetics of Cross-Linking Reaction of Epoxy Resin with Hydroxyapatite-Functionalized Layered Double Hydroxides

Polymers ◽

10.3390/polym12051157 ◽

2020 ◽

Vol 12 (5) ◽

pp. 1157 ◽

Cited By ~ 4

Author(s):

Zohre Karami ◽

Mohammad Reza Ganjali ◽

Maryam Zarghami Dehaghani ◽

Mustafa Aghazadeh ◽

Maryam Jouyandeh ◽

...

Keyword(s):

Epoxy Resin ◽

Curing Kinetics ◽

Frequency Factor ◽

Isoconversional Methods ◽

Divalent Metal Ions ◽

Interlayer Water ◽

Scanning Calorimetry ◽

Kinetics Parameters ◽

Bending Vibration ◽

Weak Band

The cure kinetics analysis of thermoset polymer composites gives useful information about their properties. In this work, two types of layered double hydroxide (LDH) consisting of Mg2+ and Zn2+ as divalent metal ions and CO32− as an anion intercalating agent were synthesized and functionalized with hydroxyapatite (HA) to make a potential thermal resistant nanocomposite. The curing potential of the synthesized nanoplatelets in the epoxy resin was then studied, both qualitatively and quantitatively, in terms of the Cure Index as well as using isoconversional methods, working on the basis of nonisothermal differential scanning calorimetry (DSC) data. Fourier transform infrared spectroscopy (FTIR) was used along with X-ray diffraction (XRD) and thermogravimetric analysis (TGA) to characterize the obtained LDH structures. The FTIR band at 3542 cm−1 corresponded to the O–H stretching vibration of the interlayer water molecules, while the weak band observed at 1640 cm−1 was attributed to the bending vibration of the H–O of the interlayer water. The characteristic band of carbonated hydroxyapatite was observed at 1456 cm−1. In the XRD patterns, the well-defined (00l) reflections, i.e., (003), (006), and (110), supported LDH basal reflections. Nanocomposites prepared at 0.1 wt % were examined for curing potential by the Cure Index as a qualitative criterion that elucidated a Poor cure state for epoxy/LDH nanocomposites. Moreover, the curing kinetics parameters including the activation energy (Eα), reaction order, and the frequency factor were computed using the Friedman and Kissinger–Akahira–Sunose (KAS) isoconversional methods. The evolution of Eα confirmed the inhibitory role of the LDH in the crosslinking reactions. The average value of Eα for the neat epoxy was 54.37 kJ/mol based on the KAS method, whereas the average values were 59.94 and 59.05 kJ/mol for the epoxy containing Zn-Al-CO3-HA and Mg Zn-Al-CO3-HA, respectively. Overall, it was concluded that the developed LDH structures hindered the epoxy curing reactions.

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

Nanomaterials ◽

10.3390/nano11081990 ◽

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.

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Co-Combustion Studies of Low-Rank Coal and Refuse-Derived Fuel: Performance and Reaction Kinetics

Energies ◽

10.3390/en14133796 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3796

Author(s):

Mudassar Azam ◽

Asma Ashraf ◽

Saman Setoodeh Setoodeh Jahromy ◽

Sajjad Miran ◽

Nadeem Raza ◽

...

Keyword(s):

Activation Energy ◽

Waste Management ◽

Energy Demand ◽

Power Plants ◽

Combustion Process ◽

Isoconversional Methods ◽

Low Rank ◽

Heating Rates ◽

Average Activation Energy ◽

Refuse Derived Fuel

In connection to present energy demand and waste management crisis in Pakistan, refuse-derived fuel (RDF) is gaining importance as a potential co-fuel for existing coal fired power plants. This research focuses on the co-combustion of low-quality local coal with RDF as a mean to reduce environmental issues in terms of waste management strategy. The combustion characteristics and kinetics of coal, RDF, and their blends were experimentally investigated in a micro-thermal gravimetric analyzer at four heating rates of 10, 20, 30, and 40 °C/min to ramp the temperature from 25 to 1000 °C. The mass percentages of RDF in the coal blends were 10%, 20%, 30%, and 40%, respectively. The results show that as the RDF in blends increases, the reactivity of the blends increases, resulting in lower ignition temperatures and a shift in peak and burnout temperatures to a lower temperature zone. This indicates that there was certain interaction during the combustion process of coal and RDF. The activation energies of the samples were calculated using kinetic analysis based on Kissinger–Akahira–Sunnose (KAS) and Flynn–Wall–Ozawa (FWO), isoconversional methods. Both of the methods have produced closer results with average activation energy between 95–121 kJ/mol. With a 30% refuse-derived fuel proportion, the average activation energy of blends hit a minimum value of 95 kJ/mol by KAS method and 103 kJ/mol by FWO method.

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Thermal and Photocatalytic Performance of Unsaturated Polyester Resins Modified with TiO2 Nanoparticles as Panel Bodies for Vehicles

Polymers ◽

10.3390/polym13132036 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2036

Author(s):

Miren Blanco ◽

Cristina Monteserín ◽

Nerea Uranga ◽

Estíbaliz Gómez ◽

Estíbaliz Aranzabe ◽

...

Keyword(s):

Tio2 Nanoparticles ◽

Energy Use ◽

Near Infrared ◽

Uv Light ◽

Unsaturated Polyester ◽

Curing Kinetics ◽

Pollutant Emissions ◽

Transport Sector ◽

Scanning Calorimetry ◽

Photocatalytic Effect

The transport sector is the fastest growing contributor to climate emissions and experiences the highest growth in energy use. This study explores the use of TiO2 nanoparticles for obtaining photocatalytic nanocomposites with improved infrared reflectance properties. The nanocomposites were prepared by dispersing 0–20 wt% of TiO2 nanoparticles in an unsaturated polyester resin. The effect of TiO2 on the curing kinetics was studied by differential scanning calorimetry, showing a significant delay of the curing reactions. The thermal reflectance of the modified resins was characterized by UV-Vis-NIR spectrophotometry, measuring total solar reflectance (TSR). The TiO2 greatly increased the TSR of the resin, due to the reflectance properties of the nanoparticles and the change in color of the modified resin. These nanocomposites reflect a significant part of near-infrared radiation, which can contribute to a reduction of the use of heating, ventilation, and air conditioning. Moreover, the photocatalytic effect of the TiO2 modified nanocomposites was studied by monitoring the degradation of an organic model contaminant in an aqueous medium under UV light, and the reusability of the nanocomposites was studied with 5 cycles. The developed nanocomposites are proposed as a solution for reducing global warming and pollutant emissions.

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Enhancement of Antioxidant and Hydrophobic Properties of Alginate via Aromatic Derivatization: Preparation, Characterization, and Evaluation

Polymers ◽

10.3390/polym13152575 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2575

Author(s):

Smaher M. Elbayomi ◽

Haili Wang ◽

Tamer M. Tamer ◽

Yezi You

Keyword(s):

Radical Scavenging Activity ◽

Radical Scavenging ◽

Hydroxyl Group ◽

Hydroxyl Groups ◽

Gravimetric Analysis ◽

Scanning Calorimetry ◽

Benzoyl Group ◽

Antioxidant Evaluation ◽

Thermo Stability

The preparation of bioactive polymeric molecules requires the attention of scientists as it has a potential function in biomedical applications. In the current study, functional substitution of alginate with a benzoyl group was prepared via coupling its hydroxyl group with benzoyl chloride. Fourier transform infrared spectroscopy indicated the characteristic peaks of aromatic C=C in alginate derivative at 1431 cm−1. HNMR analysis demonstrated the aromatic protons at 7.5 ppm assigned to benzoyl groups attached to alginate hydroxyl groups. Wetting analysis showed a decrease in hydrophilicity in the new alginate derivative. Differential scanning calorimetry and thermal gravimetric analysis showed that the designed aromatic alginate derivative demonstrated higher thermo-stability than alginates. The aromatic alginate derivative displayed high anti-inflammatory properties compared to alginate. Finally, the in vitro antioxidant evaluation of the aromatic alginate derivative showed a significant increase in free radical scavenging activity compared to neat alginate against DPPH (2,2-diphenyll-picrylhydrazyl) and ABTS free radicals. The obtained results proposed that the new alginate derivative could be employed for gene and drug delivery applications.

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