Multiple Heating Rate Method Research Articles

Kinetics of the thermal decomposition of thermally reduced graphene oxide treated with a pulsed high-frequency discharge in hydrogen atmosphere

Thermal stability and the kinetics of thermal decomposition of the thermally reduced graphene oxide (TRGO) treated by a pulsed high-frequency discharge in a hydrogen atmosphere have been studied. The modified Hummers method was used for obtaining the initial graphite oxide from graphite powder. Thermal exfoliation of the graphene oxide powder has been done in vacuum conditions with a heating rate of 5–7 degrees per minute to a temperature of 300 °С. TRGO has been treated by pulsed high-frequency discharge in a hydrogen atmosphere for partial graphene hydrogenation (chemical addition of atomic hydrogen) that leads to structural changes in the carbon planes and formation of C–H sp3 bonds. The thermogravimetry analysis measurements of the mass loss have been carried from room temperature to 1000 °C in a nitrogen atmosphere with a nitrogen flow rate of 20 mL/min and different heating rates: 50, 75 100, 125, 150, and 200 K/min, respectively. Kissinger’s multiple heating rate method has been used to determine the activation energy for decomposing substances. Activation energies Ea1, Ea2, and Ea3 equal 28, 50, and 148 kJ/mol, respectively, have been compared with the energies of the activation of thermal defunctionalization of multiwalled carbon nanotubes (MWCNTs). The activation energy Ea3 = 148 kJ/mol is close to that of the thermal decomposition of anhydride functional groups in MWCNT. The value of Ea2 = 50 kJ/mol indicates the presence of the keto and hydroxy acid’s function groups on TRGO. Activation energy Ea1 = 28 kJ/mol related with all other groups including the lighter C–H bonds that destructed due to dehydrogenation of the TRGO. Obtained experimental results are useful for further proposing the kinetic model of the mechanism of the most probable reaction of TRGO decomposition.

Qualifying the cathode aging process for storage life prediction for primary AgO-Zn batteries

AgO-Zn batteries are widely recognized for their high energy density, specific capacity, and safety features. Especially the AgO-Zn reserve battery, which possesses good storage stability to better adapt to the application requirements of long-term storage, is considered an ideal candidate for applications in military, aerospace, and other fields. However, since there are only a few studies on the decomposition kinetic of the cathode for the AgO-Zn reserve battery, further in-depth research is needed on the aging mechanism. Herein, we conduct a comprehensive investigation of the aging behavior of the cathode in commercial AgO-Zn reserve batteries. The physicochemical properties of the cathodes with different storage years are characterized by multiple methods, including phase composition, surface morphology, and thermal behaviors. The evolution of structure and performance for the cathodes with storage time and their impact on the electrical performance of AgO-Zn batteries are studied. In addition, a multiple heating rate method is performed to determine the thermal decomposition kinetics of the cathode. Based on the obtained kinetic parameters, a model for the decomposition of the AgO in the cathode is developed, enabling the estimation of theoretical storage time for achieving the cathode with the same retention rate as actual storage in a shortened time by accelerated aging. Validation studies comparing accelerated aging results with real-time aging under natural conditions are further performed to assess the reliability of the accelerated aging model. This research provides insights into the aging mechanisms of cathode for AgO-Zn batteries and offers a systematic approach for the accelerated aging test, paving the way for the development of the prediction of battery performance and lifespan.

Analysis on the thermal decomposition kinetics and storage period of biomass-based lycorine galanthamine.

As global ageing deepens and galanthamine is the preferred clinical drug for the treatment of mild to moderate Alzheimer's disease, it will be valuable to examine the behaviour and mechanism of galanthamine's thermal decomposition for its quality control, formulation process, evaluation of thermal stability, and expiry date in production. In order to study the pyrolysis of galanthamine hydrobromide with nitrogen as the carrier gas, a thermogravimetric-differential thermogravimetric technique (TG-DTG) was applied at a temperature rise rate of 10Kmin-1 and a volume flow rate of 35mLmin-1. The apparent activation energy E a and the prefactor A (E a = 224.45kJmol-1 and lnA = 47.40) of the thermal decomposition reaction of galanthamine hydrobromide were calculated according to the multiple heating rate method (Kissinger and Ozawa) and the single heating rate method (Coats-Redfern and Achar), and the most probable mechanism function was derived, and then the storage period was inferred from E a and E. A three-dimensional diffusion mechanism was suggested to control the thermal decomposition of galanthamine hydrobromide in accordance with the Jander equation, random nucleation and subsequent growth control, corresponding to the Mample one-way rule and the Avrami-Erofeev equation. As a result, the thermal decomposition temperature of galanthamine hydrobromide gradually increased with the rate of temperature rise. From Gaussian simulations and thermogravimetric data, galanthamine hydrobromide decomposed at the first stage (518.25-560.75K) to release H2O, at the second stage (563.25-650.75K) to generate CO, CO2, NH3 and other gases, and finally at the third stage (653.25-843.25K) to release CO2. After 843.25K, the residual molecular skeleton is cleaved to release CO2 and H2O. According to the E a and A presenting in the first stage of thermal decomposition, it is assumed that the storage life of galanthamine hydrobromide at room temperature 298.15K is 4-5years.

Thermal properties and pyrolysis kinetics of phosphate-rock acid-insoluble residues

In the phosphorous–sulphur two-step process for the clean production of phosphoric acid, a phosphate-rock acid-insoluble residue (PAIR) is a solid filter residue obtained via the phosphoric acid acidolysis of phosphate rock (PR). PAIR combined with other raw materials can be used to prepare cement, ceramics and glasses, opening a potential avenue for large-scale PAIR utilisation. However, the preparation of such materials requires high-temperatures calcination. Understanding the high-temperature thermal properties of PAIR can enable its more targeted comprehensive utilisation or disposal. In this study, the thermal properties and pyrolysis kinetics of PAIR were systematically studied using a multiple heating rate method based on thermogravimetric analysis and a kinetic model. Results showed that from room temperature to 1200 °C, the main changes in the PAIR were the complete removal of fluorine and sulphur, partial removal of phosphorus and conversion of quartz to cristobalite. Moreover, during these processes, H2O(g), NH3, N2, CO2, SO2, P2O5(g), CO, CF3+ and organic gases were volatilised. Herein, the pyrolysis kinetics of PAIR is divided into five stages. Stage 1 (conversion rate ɑ: 0.05–0.2) conforms to the random nucleation and growth as well as the Avrami–Erofeev (n = 2/3) mechanism; the corresponding mechanism function is F(ɑ) = [−Ln(1 − ɑ)]2/3. Stage 2 (ɑ: 0.2–0.4) conforms to the first-order chemical reaction mechanism; the corresponding mechanism function is F(ɑ) = −Ln(1 − ɑ). Stage 3 (ɑ: 0.4–0.6) conforms to the phase boundary–controlled reaction and one-dimensional movement mechanism; the corresponding mechanism function is F(ɑ) = ɑ. Stage 4 (ɑ: 0.6–0.8) conforms to the three-dimensional diffusion process (Jander model); the corresponding mechanism function is F(ɑ) = [1 − (1 − ɑ)1/3]2. Stage 5 (ɑ: 0.6–0.95) conforms to the one-dimensional diffusion process; the corresponding mechanism function is F(ɑ) = ɑ2.

Combustion and pyrolysis kinetics of Australian lignite coal and validation by artificial neural networks

Lignite (AL), with a calorific value of 5.9 MJ/kg is the most abundant low-rank coal used widely in power generation. AL's combustion and pyrolysis characteristics were investigated to provide scientific findings using thermogravimetric analysis under non-isothermal conditions. Methods utilized in the kinetic investigation included Vyazovkin, Flynn-Ozawa-Wall (FOW), Kissinger-Akahira-Sunose (KAS), Freidman, Doyle, Arrhenius, Freeman-Caroll, and Sharp-Wentworth. Multiple heating rate methods delivered the activation energy (Ea) as 194–211 kJ/mol (combustion) and 450–470 kJ/mol (pyrolysis). Combustion process followed two dimensional diffusional reaction (2D), volume contracting (R3) solid-state reaction mechanism models and pyrolysis followed volume contracting (R3) as determined by CR (Coats-Redfern), KC (Kennedy-Clark) methods. Master Plot method validated the mechanisms and concluded that it is of deaccelerating type. Improper combustion at a higher heating rate (50 °C/min) was indicated with an increase in burnout Tb, ignition Ti, peak Tp temperatures. Combustion indices (CHCI, IG, IB) reported highest values of 4.99 E−10 mg2 min−2 OC−3, 4.19E-05 mg2 min−3, 2.65 mg2 min−4 at lowest heating rates. AL's analytical thermal degradation behavior results were validated using artificial neural networks with best-fit models NNA 7,8. The research study offers a useful guide for spontaneous AL combustion and pyrolysis prediction on site.

Kinetic analysis of urethane formation between castor oil-based ester polyol and 4,4’-diphenyl methane diisocyanate

ABSTRACT Kinetics of urethane formation between castor oil-based ester polyol (COEP) and 4,4′diphenyl methane diisocyanate (MDI) was evaluated using Differential Scanning Calorimeter (DSC) technique. The autocatalytic effect of urethane groups during polyurethane formation was confirmed through this study. DSC runs were made under dynamic heating schedule at various heating rates, viz.: 5, 10, 15 and 20 K/min. Single Heating rates like Chatterjee–Conrad and multiple heating rate method like Ozawa models were used to evaluate the kinetic parameter. Isocyanate index (Eq. of NCO/Eq. of OH) of 1 was used for the reaction between COEP and MDI. DSC thermograms exhibit two isotherms at 70°C and 120°C. Kinetic parameters adopting different models, in terms of activation energy, suggest that the urethane formation occurs grossly in two stages: the first step being standard uncatalysed urethane reaction and the following second step presumably autocatalysed urethane formation. The two exotherms were resolved into two portions. Kinetic analysis was undertaken for the unresolved DSC as well as the resolved ones, treating the resolved thermograms as the outcome of two independent competing reactions.

Correlation between the cross-linking and degradation activation energy of cotton fabric treated with chitosan kinetic study by ‘model-free’ multiple heating rate methods

The different concentrations of chitosan were applied on cotton fabrics using glutaraldehyde as a cross-linking agent. The fabric samples were thermally analysed from ambient temperature to 700 °C at four different linear heating rates, i.e. 2.5, 5, 10 and 20 °C min−1 in a flowing nitrogen medium. Non-isothermal ‘model-free’ multiple heating rate methods like Friedman and Kissinger–Akahira–Sunose have been employed for the determination of degradation activation energy of the samples. The degradation mechanism based on activation energy calculation at different conversions has been proposed and compared with the extent of cross-linking. Also the method of universal master plots has been employed on isothermal data and worked on different models and their optimizations. This research work tries to achieve a correlation between activation energy and extent of cross-linking with the increase in chitosan concentration to the fabric.

Study on Thermal Decomposition Behaviors of Terpolymers of Carbon Dioxide, Propylene Oxide, and Cyclohexene Oxide.

The terpolymerization of carbon dioxide (CO2), propylene oxide (PO), and cyclohexene oxide (CHO) were performed by both random polymerization and block polymerization to synthesize the random poly (propylene cyclohexene carbonate) (PPCHC), di-block polymers of poly (propylene carbonate–cyclohexyl carbonate) (PPC-PCHC), and tri-block polymers of poly (cyclohexyl carbonate–propylene carbonate–cyclohexyl carbonate) (PCHC-PPC-PCHC). The kinetics of the thermal degradation of the terpolymers was investigated by the multiple heating rate method (Kissinger-Akahira-Sunose (KAS) method), the single heating rate method (Coats-Redfern method), and the Isoconversional kinetic analysis method proposed by Vyazovkin with the data from thermogravimetric analysis under dynamic conditions. The values of ln k vs. T−1 for the thermal decomposition of four polymers demonstrate the thermal stability of PPC and PPC-PCHC are poorer than PPCHC and PCHC-PPC-PCHC. In addition, for PPCHC and PCHC-PPC-PCHC, there is an intersection between the two rate constant lines, which means that, for thermal stability of PPCHC, it is more stable than PCHC-PPC-PCHC at the temperature less than 309 °C and less stable when the decomposed temperature is more than 309 °C. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetric analysis/infrared spectrometry (TG/FTIR) techniques were applied to investigate the thermal degradation behavior of the polymers. The results showed that unzipping was the main degradation mechanism of all polymers so the final pyrolysates were cyclic propylene carbonate and cyclic cyclohexene carbonate. For the block copolymers, the main chain scission reaction first occurs at PC-PC linkages initiating an unzipping reaction of PPC chain and then, at CHC–CHC linkages, initiating an unzipping reaction of the PCHC chain. That is why the T−5% of di-block and tri-block polymers were not much higher than that of PPC while two maximum decomposition temperatures were observed for both the block copolymer and the second one were much higher than that of PPC. For PPCHC, the random arranged bulky cyclohexane groups in the polymer chain can effectively suppress the backbiting process and retard the unzipping reaction. Thus, it exhibited much higher T−5% than that of PPC and block copolymers.

Thermal and biological studies of Schiff bases of chitosan derived from heteroaryl aldehydes

The synthesis of Schiff bases of chitosan is performed by the reaction of chitosan with different heteroaryl aldehydes, i.e., furfuraldehyde, thiophene-2-carboxylaldehyde, pyrrole-2-carboxylaldehyde, pyridine-2-carboxylaldehyde, pyridine-3-carboxylaldehyde and pyridine-4-carboxylaldehyde. The structural characterizations of the biopolymeric Schiff bases are executed by 1H NMR spectroscopy, Fourier transform infrared spectroscopy and elemental analysis (C, H, N). The 1H NMR spectroscopy is also used to determine the degree of deacetylation of chitosan as well as the degree of substitution (DS) of Schiff bases and DS found to be varying from 58 to 74%. Thermogravimetry studies of chitosan and its Schiff base polymers show that they have nearly the same decomposition temperature and hence equally thermally stable. The model-free multiple heating rate method Kissinger–Akahira–Sunose has been employed for the thermal degradation kinetics of the most potent antimicrobial compound ChSB-6. The antimicrobial activities of chitosan and its Schiff bases are tested against different pathogenic bacteria: Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Aspergillus niger, and results shows that the activities of the Schiff bases of chitosan are found to be stronger than that of chitosan.

Thermo-oxidative degradation kinetics of grafted polypropylene films

ABSTRACTThe thermo-oxidative stability and degradation behavior of polypropylene (PP) and grafted PP have been investigated using thermogravimetric analysis. Three multiple heating rate methods, namely Kissinger, Kim–Park and Flynn–Wall have been used to calculate the activation energy as a function of the extent of degradation. The four different heating rates (5, 10, 15 and 20°C/min) were maintained in the temperature range of 30–550°C during the analysis. Fourier transform infrared spectroscopy has confirmed the presence of carboxylic group on the surface of grafted PP films. Differential scanning calorimetry has shown that the crystallinity decreased with the increase in grafting. In the air atmosphere, the thermo-oxidative degradation occurs via a pathway that involves decomposition of polymer peroxide. Thermo-oxidative stability of grafted PP films is found to increase with an increase in the degree of grafting (DG). The degradation kinetic parameters were used to predict the lifetime of PP and grafted PP films. The activation energy and lifetime of grafted PP films increased with an increase in the DG. The lifetime of PP and grafted PP decreased with an increase in degradation temperature.

Thermal degradation kinetics and estimation of lifetime of radiation grafted polypropylene films

In this research work, thermal stability and degradation behavior of acrylic acid grafted polypropylene (PP-g-PAAc) films were investigated by using thermogravimetric (TGA) analysis at four different heating rates 5, 10, 15 and 20°C/min over a temperature range of 40–550°C in nitrogen atmosphere. The kinetic parameters namely activation energy (Ea), reaction order (n) and frequency factor (Z) were calculated by three multiple heating rate methods. The thermal stability of PP-g-PAAc films is found to decrease with increase in degree of grafting. The TGA data and thermal kinetic parameters were also used to predict the lifetime of grafted PP films. The estimated lifetime of neat PP as well as grafted PP decreased with increase in temperature by all the three methods. Studies also indicated that Ea and lifetime of PP-g-PAAc films decreased with increase in degree of grafting, which may also be helpful in biodegradation of grafted PP films.

Studies on the thermal properties of silicone polymer based thermal protection systems for space applications

Thermal decomposition, thermal conductivity, specific heat and flammability of polydimethyl siloxane (PDMS) resin and three PDMS-based systems with three different types of additives were studied using various thermo-analytical techniques. The additives were found to modify the thermal properties of PDMS to different extents. Among the three systems, highest specific heat and lowest thermal conductivity, desired for thermal protection application, were obtained for System I. The thermal stability of the three systems is in the order System I > System II > System III. Even though System III showed the lowest specific heat and highest thermal conductivity, due to its very high LOI among all other systems, the system finds application as a flame retardant. Thermogravimetric–mass spectroscopic analysis was carried out to find out the decomposition products. The major decomposition product was identified as hexamethylcyclotrisiloxane in all the systems. The decomposition kinetics of these systems was investigated by thermogravimetry using multiple heating rate methods, viz. Kissinger and Flynn–Wall–Ozawa. The kinetic parameters, viz. activation energy and pre-exponential factor, were derived using the two methods for all the systems. From the kinetic study, it is confirmed that the activation energy for the decomposition of the neat PDMS decreased as decomposition progressed, whereas the activation energy increased for the silicone composite systems.

Nonisothermal and isothermal oxidative degradation behavior of thermotropic liquid crystal polyesters containing kinked bisphenol AF and bisphenol A units

The polyester P–bisphenol AF 2.5 (BPAF 2.5) and P-bisphenol A 2.5 (BPA 2.5) with low melting temperature and high glass transition temperature can be obtained by introducing 2.5 mol% BPAF/BPA and terephthalic acid (TA) units respectively into the molecular chain of poly(oxybenzoate- co-oxynaphthoate) (P-HBA70). In this study, the nonisothermal and isothermal oxidative degradation behavior of polyester P-BPA2.5 and P-BPAF2.5 were investigated comparatively with parent polyester P-HBA70 by thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy measurements. The introduction of BPAF/BPA units into the molecular chain of P-HBA70 strongly influenced the degradation behavior of polyesters. Four multiple heating rate methods including Kissinger, Kim–Park, Flynn–Wall–Ozawa, and Friedman methods were applied to evaluate the dynamic thermal stability successfully. The following order of the activation energy values: P-BPAF2.5 > P-HBA70 > P-BPA2.5 can be found for the three samples. However, from the results obtained by the standard isoconversional method, the P-BPA2.5 showed a better thermal stability as compared to P-BPAF2.5 under isothermal atmosphere.

Synthesis, characterization and thermal decomposition kinetics of poly(2-imidazolidinthione-formaldehyde)

A polymeric ligand, 2-imidazolidinthione-formaldehyde (poly-IF), bearing nitrogen and sulfur donor group was synthesized by the polycondensation of 2-imidazolidinthione and formaldehyde in alkaline medium. The synthetic ligand was characterized with micro-analytical and spectral studies. The thermal degradation is investigated by means of dynamic thermogravimetry (TG/DTG) in helium and air atmosphere at various heating rate. The non-isothermal degradation of poly-IF compound was occurred in an inert and air atmosphere. Degradation activation energies were calculated using model free multiple heating rate methods i.e. Flynn-Wall-Ozawa (FWO), Friedman and Kissinger. The compound poly-IF was also tested against strain ( Escherichia coli ) and it inhibits the proliferation of bacterial growth.

Thermal analysis, decomposition kinetics, and molecular modeling of transition metal (Fe, Co) surfactant complexes

A detailed thermal analysis of iron and cobalt surfactant complexes of the type [M(CH3COO)4]2−[C12H25NH3 +]2 has been carried out using Thermogravimetric (TG) analysis at different heating rates (i.e., 5, 10, 15, and 20 °C min−1). It has been observed that iron complex decomposes by a different mechanism compared to other transition metal complexes. Metal is the final product instead of metal oxide. Combining the results from our previous study, first row transition metal complexes exhibit an order of stability in agreement with the famous Irving Williams series, i.e., the apparent activation energy, E for thermal decomposition varies as: E Fe > E Co < E Ni < E Cu > E Zn (exception being iron because of different decomposition mechanism). Thermal decomposition parameters have been measured and compared using the multiple heating rate method of Flynn–Wall–Ozawa. Further, molecular modeling calculations have been carried out to compare the experimental TG data with theoretical computations for the synthesized metal surfactant complexes. Minimum energy optimized structures for the complexes have been obtained using Gaussian software.

A comparison of direct methods to determine n-th order kinetic parameters of solid thermal decomposition for use in fire models

Pyrolysis models for burning solids in fire simulations are sensitive to the values of the activation energy, frequency factor, and reaction order that characterize the thermal decomposition of the solid to gaseous fuel, so direct measurement of these kinetic parameters is recommended, and simple methods are preferred. Three direct methods were evaluated with regard to the ability of their kinetic parameters to reproduce the thermal decomposition of five polymers measured by differential thermogravimetric analysis using the reaction order model. It was found that the two multiple heating rate methods produced identical, physically based kinetic parameters, while the peak property method produced non-physical kinetic parameters. However, all of these kinetic parameters in a single-step reaction order model gave reasonably good conversion histories for non-charring and moderately charring polymers. For a highly charring polymer, the conversion histories were poorly described without a multiple step reaction. The temperature at the maximum rate of conversion was found to be essentially independent of the reaction order, which decouples the frequency factor from the reaction order in the direct kinetic methods. Any of the direct methods are sufficiently accurate to obtain kinetic parameters for pyrolysis models because of the inherent spatial and temporal averaging of reaction rates at the burning surface of a thick solid and the uncertainty in the heat transfer mechanisms and thermo-physical parameters used in the models.

Curing kinetics and thermal stability of epoxy blends containing phosphorous-oxirane with aromatic amide-amine as curing agents

This article describes the synthesis of a series of aromatic amide-amines and their potential use as epoxy hardeners. These amines were synthesized by the reaction of L-phenylalanine (PA) with diamines of different structures i.e. 1,4-phenylene diamine (PD), 1,5-diamino naphthalene (N), 4,4′-(9-fluorenyllidene)-dianiline (F), 4,4′-diaminodiphenyl sulphide (DS) and 3,4′-oxydianiline (O) in a stoichiometric ratio (1:1). Structural characterization of synthesized amide-amines was done with the help of elemental analysis and spectroscopic techniques viz. FT-IR, 1H-NMR and 13C-NMR. An epoxy blend was prepared by mixing tris(glycidyloxy) phosphine oxide (TGPO) with conventional epoxy i.e. diglycidyl ether of bisphenol-A (DGEBA) in an equivalent ratio of 2:3 to incorporate phosphorous into the main chain. The curing kinetics of the epoxy blend with synthesized aromatic amide-amines was investigated by non-isothermal DSC technique using multiple heating rate method (5, 10, 15 and 20 K/min.). The activation energies were determined by fitting the experimental data into Kissinger and Ozawa kinetic models. The activation energies obtained through Ozawa method were slightly higher than those of Kissinger method but were comparable. However, both the energies were found to be dependent on the structure of amines. The thermal stability and weight loss behavior of isothermally cured thermosets were also investigated using thermogravimetric analysis (TGA) in nitrogen atmosphere. All the samples showed improved thermal stability in terms of char yield than using only amines as hardeners.

Catalytic effect of bases in impregnation of guanidine nitrate on Poplar (Populus) wood

Wood, one of the flammable material, was treated with aqueous solution of guanidine nitrate (GUN) and also with small amount of bases like N,N-dimethylformamide, 4-dimethylaminopyridine, pyridine, and triethylamine in the treating solution. These bases catalyze the impregnation of GUN as indicated by increase in mass gain percentage, elemental analysis, and scanning electron microscopy. To study their thermal behavior, dynamic thermogravimetry (TG) and derivative thermogravimetry (DTG) analysis under nitrogen atmosphere have been applied from ambient temperature to 973 K on all samples, at multiple linear heating rates 2.5, 5, 10, and 20 K min−1. Non-isothermal, “model free” iso-conversional multiple heating rate methods, Ozawa–Flynn–Wall (O–F–W) and modified Coats–Redfern are used to calculate activation energy of samples. The activation energy of samples is found in the range 109–208 kJ mol−1. Thermal parameters like overall pyrolysis duration, maximum mass loss rate, corresponding to DTG peak maximum and percentage char yield calculated at 873 K from TG curves are used to appraise the flammability of samples. Also, flammability of samples is determined by reliable methods namely limiting oxygen index and underwriters laboratories 94 (UL 94) test. The aforesaid study indicates that base catalyzed impregnated samples are less flammable than those impregnated with only GUN and untreated ones.

Curing and thermal behaviour of DGEBA using mixture of biuret and 4,4′-diaminodiphenylsulfone

Curing behaviour of DGEBA was investigated in the presence of varying molar ratio of biuret and 4,4′-diaminodiphenylsulfone (DDS) by means of Differential scanning calorimetery. The multiple heating rate method (5, 10, 15 and 20 °C min−1) was used to study the curing behaviour of epoxy resins. The peak exotherm temperature was found to be dependent on the heating rates, structure of biuret as well as on the ratios of biuret:DDS used. Ozawa method was used for calculating the activation energy of curing reaction. The thermal stability of the isothermally cured resins was evaluated by recording the thermogravimetric traces in nitrogen atmosphere. All the samples were stable up to 330 °C.

Studies on curing kinetics and thermal behavior of phosphorylated epoxy resin in the presence of aromatic amide‐amines

AbstractThis article describes the synthesis of some novel aromatic amide‐amine curing agents by reacting 1 mole of p‐amino benzoic acid with 1 mole of each of 1,4‐phenylene diamine (P), 1,5‐diamino naphthalene (N), 4,4′‐(9‐fluorenyllidene)‐dianiline (F), 3,4′‐oxydianiline (O), and 4,4′‐diaminodiphenyl sulphide (DS) and were designated as PA, NA, FA, OA, and SA, respectively. The aromatic amide‐amines so synthesized were characterized with the help of spectroscopic techniques, viz., Fourier Transform Infrared, proton nuclear magnetic resonance, and carbon nuclear magnetic resonance. The curing kinetics of the epoxy resins obtained by reacting amines with diglycidyl ether of bisphenol‐A blended with tris(glycidyloxy)phosphine oxide in a ratio of 3 : 2, respectively, were investigated by DSC technique using multiple heating rate method (5, 10, 15, 20°C/min). Activation energies were determined by fitting the experimental data into Kissinger and Flynn‐Wall‐Ozawa Kinetic models. The activation energies obtained through Flynn‐Wall‐Ozawa method were slightly higher than Kissinger method but were comparable. However, both the energies were found to be dependent on the structure of amines. The thermal stability and weight loss behavior of isothermally cured thermosets were also investigated using thermogravimetric analysis in nitrogen atmosphere. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010