Kissinger Model Research Articles

Effects of graphene oxide size on curing kinetics of epoxy resin.

To study the effects of graphene oxide (GO) size on the curing kinetics of epoxy resin (EP), two kinds of GO were selected and characterized by Fourier transform infrared spectrometry (FT-IR), FT-Raman spectrometry (FTIR-Raman), thermo gravimetric analysis (TGA), dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that the two kinds of GO had similar chemical structures but different sizes—the average particle size of GO-A was 190.1 nm and that of GO-B was 1510 nm, and GO-A has more oxidizing groups on its surface. The two kinds of GO were separately added to EP, and the curing kinetics of GO/EP composites and neat EP were investigated through differential scanning calorimetry (DSC). It can be seen that the addition of GO promoted the curing process of the EP system, and GO-A had a more significant catalytic effect. Furthermore, the curing activation energy (Ea) was calculated by Kissinger model, and the change of Ea in the whole curing reaction process was studied by Ozawa method to further understand the curing mechanism. It showed that the apparent Ea of EP system increases with the increase of the conversion rate, and Ea of EP-A is obviously lower in the early curing stage. However, as the curing reaction proceeds, Ea of EP-B is a little lower than that of EP-A in the later curing stage. But EP-A has the lowest Ea combined with the whole process from Kissinger method. To sum up, it can be concluded that the curing process of EP can be promoted by adding GO and the smaller size (190.1 nm) of GO had a greater effect and lower Ea than the GO with particle size of 1510 nm. And the related mechanisms were discussed and analyzed.

Solid-State Polymerization as a Vitrimerization Tool Starting from Available Thermoplastics: The Effect of Reaction Temperature.

In the current work, solid-state polymerization (SSP) was studied for the synthesis of poly(butylene terephthalate), PBT-based vitrimers. A two-step process was followed; the first step involved alcoholysis reactions and the incorporation of glycerol in the polymer chains. The second step comprised transesterification reactions in the solid state (SSP) in the presence of zinc(II) catalyst resulting in the formation of a dynamic crosslinked network with glycerol moieties serving as the crosslinkers. The optimum SSP conditions were found to be 3 h at 180 °C under N2 flow (0.5 L/min) to reach high vitrimer insolubility (up to 75%) and melt strength (2.1 times reduction in the melt flow rate) while increasing the crosslinker concentration (from 3.5 to 7 wt.%) improved further the properties. Glass transition temperature (Tg) was almost tripled in vitrimers compared to initial thermoplastic, reaching a maximum of 97 °C, whereas the melting point (Tm) was slightly decreased, due to loss of symmetry perfection under the influence of the crosslinks. Moreover, the effect of the dynamic crosslinked structure on PBT crystallization behavior was investigated in detail by studying the kinetics of non-isothermal crystallization. The calculated effective activation energy using the Kissinger model and the nucleating activity revealed that the higher crosslinker content impeded and slowed down vitrimers melt crystallization, also inducing an alteration in the crystallization mechanism towards sporadic heterogeneous growth.

Catalyst-free synthesis of isocyanate-blocked imidazole and its use as high-performance latent hardener for epoxy resin

Catalyst-free synthesis in three kinds of isocyanate-blocked imidazole compound was successfully achieved by chemically connecting 2-ethyl-4-methylimidazole (2E4MI) with hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI) or 4,4′-diphenylmethane diisocyanate (MDI), which were tested as the latent hardeners for epoxy (EP) resins. The chemical structures of the synthesized HDI-2E4MI, TMHDI-2E4MI and MDI-2E4MI were identified with Fourier transform infrared spectroscope (FTIR), 1H and 13C nuclear magnetic resonance (1H NMR and 13C NMR). Based on characterizations including thermogravimetry/differential scanning calorimetry (TG/DSC) simultaneous testing and hot-stage FTIR, it was found that both HDI-2E4MI and TMHDI-2E4MI exhibited two-step deblocking behavior, whereas the deblocking process of MDI-2E4MI was completed only via one step. Curing kinetics of HDI-2E4MI/EP, TMHDI-2E4MI/EP and MDI-2E4MI/EP systems were then studied by non-isothermal DSC using Kissinger model. The results revealed that MDI-2E4MI/EP system could be cured via a two-step reaction with the highest curing rate due to the high reactivity of MDI-2E4MI, which was much different from the four-step curing behaviors of both HDI-2E4MI/EP and TMHDI-2E4MI/EP systems. Compared to the reference 2E4MI, noticeably, the three synthesized hardeners showed the outstanding latent features with lower curing activity and longer shelf life and the EP systems cured by the hardeners exhibited desirable mechanical properties and thermal stability. This study provided a feasible approach to synthesize high-performance imidazole-based latent hardener for wide practical applications in a greenway via the blocking treatment through tailoring the isocyanate structure.

Thermal Degradation Kinetics of ZnO/polyester Nanocomposites.

ZnO particles were synthetized by the sol–gel method and subsequent heat treatment of 400, 500 and 600 °C was applied. The nano ZnO particles were incorporated to the unsaturated polyester resin by solution blending at 0.05 wt % concentration. X-ray diffraction detected the formation of a wurtzite-like structure. Viscoelastic behavior of neat polyester and nanocomposites revealed the nano ZnO particles does not promote better mechanical properties because of a weak interaction and the glass transition temperature of the polyester was favored by the presence of a higher quantity of nano-size ZnO particles. Thermogravimetric analysis at 5, 10 and 20 °C/min allowed determining the degradation kinetic parameters based on the Friedman and Kissinger models for neat polyester and nanocomposites. Heating rates promoted an increase in the temperature degradation and the addition of ZnO particles promoted a catalyst effect that reduce the amount of thermal energy needed to start the thermal degradation.

Effect of Cooling Rate on Precipitation Behavior of Gamma Prime in a Newly Developed Co-based Superalloy

The influence of the cooling rate on the precipitation behavior of gamma prime (γ′) in a newly developed Co-based superalloy has been investigated by using differential scanning calorimetry. In addition, changes to the γ′ precipitate morphology and size were analyzed by scanning electron microscopy. It was observed that increasing the rate at which the alloy was cooled from high temperatures increased the γ′ precipitation rate at different temperatures but also reduced the temperature at which the maximum precipitation rate occurred and retarded the complete precipitation of the γ′ precipitates. The activation energy required for γ′ precipitation was calculated by using the Kissinger model, revealing that the present alloy exhibits higher activation energy than some Ni-based superalloys, which can be attributed to lower rates of atomic diffusion in cobalt-based superalloys.

Thermochemical conversion of Parthenium hysterophorus biomass for bio-oil synthesis: kinetics and techno-economic analysis

A single-stage fixed bed reactor was fabricated to study the thermochemical conversion of Parthenium hysterophorus biomass. Parthenium hysterophorus biomass was subjected to proximate analysis, ultimate analysis, and gross calorific value analysis. Thermogravimetric analyses of Parthenium hysterophorus were performed at 5 °C min−1, 10 °C min−1, and 15 °C min−1. Parthenium hysterophorus pyrolysis was performed at 400 °C to 600 °C with a temperature ramp of 50 °C. The yield of bio-oil was estimated to be 23.11%, 25.80%, 30.12%, 32.30%, and 30.93%, at 400 °C, 450 °C, 500 °C, 550 °C, and 600 °C, respectively. The kinetic parameters were evaluated with model free methods. The Kissinger model reported a mean activation energy of 108.58 kJ mol−1. The Kissinger-Akahira-Sunose model, Ozawa-Flynn-Wall model, and Friedman model reported a mean activation energy of 163.50 kJ mol−1, 169.67 kJ mol−1, and 297.13 kJ mol−1, respectively. The volatile and semi-volatile compounds in the bio-oil were analyzed using a gas chromatography-mass spectrometer (GC-MS). A nondestructing X-ray fluorescence analysis was performed for determination of elemental composition and ash content. A flue gas analyzer quantified the pyro-gas composition. Energy and exergy analysis of pyro-gas from Parthenium hysterophorus inscripts the uniqueness of the study. The maximum energy efficiency for thermochemical conversion of Parthenium hysterophorus was 73.19%. The maximum exergy was estimated to be 61.37% at 600 °C. The exergy efficiency of the thermochemical conversion of Parthenium hysterophorus increased by 30% at 600 °C in comparison with thermochemical conversion at 400 °C. The anergy value was estimated to be 2.3 MJ kg−1 at 600 °C. Techno-economic analysis of the Parthenium hysterophorus pyrolysis was also reported.

Thermal analysis of the crystallization kinetics of lead zirconate titanate powders prepared via sol–gel route

The crystallization evolution of lead zirconate titanate (PZT) powders processed from two organic gel systems with nominal composition was investigated. The crystallization of the perovskite PZT form initiated as the calcining temperature reached 400 °C. The formation of PbO phase constituted seeding grains for PZT crystallization at such low temperature. The formation of lead-deficient fluorite or pyrochlore phases was completely avoided under judicious processing conditions. TGA/DTA analysis was carried out to evaluate the activation energy associated with the perovskite phase formation. The kinetic parameters of the PZT crystallization toward perovskite formation were followed by employing Kissinger and JMAK isoconversional kinetic models. The results revealed that the crystallization mechanism is related to the powder precursor system. The value of the activation energy for the perovskite formation was about 77 kJ mol−1 irrespective of the precursor system when the Kissinger model was applied.

Effect of Silver Nanoparticles on the Microstructure, Non-Isothermal Crystallization Behavior and Antibacterial Activity of Polyoxymethylene.

Silver (Ag) nanoparticles were synthesized by a facile route in the presence of oleic acid and n-propylamine. It was shown that the average primary size of the as-synthesized Ag nanoparticles was approximately 10 nm and the surface of as-synthesized Ag nanoparticles was capped with monolayer surfactants with the content of 19.6%. Based on as-synthesized Ag nanoparticles, polyoxymethylene (POM)/Ag nanocomposites were prepared. The influence of Ag nanoparticles on non-isothermal crystallization behavior of POM was investigated by differential scanning calorimetry (DSC). The Jeziorny, Jeziorny-modified Avrami, Ozawa, Liu and Mo, Ziabicki and Kissinger models were applied to analyze the non-isothermal melt crystallization data of POM/Ag nanocomposites. Results of half time (t1/2), crystallization rate parameter (CRP), crystallization rate function (K(T)), kinetic parameter (F(T)), the kinetic crystallizability at unit cooling rate (GZ) and the crystallization activation energy (∆E) were determined. Small amounts of Ag nanoparticles dispersed into POM matrix were shown to act as heterogeneous nuclei, which could enhance the crystallization rate of POM, increase the number of POM spherulites and reduce POM spherulites size. However, the higher loading of Ag nanoparticles were easily aggregated, which restrained POM crystallization to some degree. Furthermore, the POM/Ag nanocomposites showed robust antibacterial activity against Escherichia coli and Staphylococcus aureus.

Study of transition kinetics of Se80Te20−xInx chalcogenide glasses

Chalcogenide glasses with the chemical formula Se80Te20−xInx (x = 5, 10 and 15) were prepared using the melt quenching method. The amorphous nature of the prepared samples was checked by X-ray diffraction analysis. The thermal behavior was investigated by using differential scanning calorimetry at different heating rates, 5, 10, 15 and 20 °C/min. Lasocka relation was used to study the heating rate dependence of the glass and crystallization temperatures. Kissinger and Mahadevan models were used to determine the glass and crystallization activation energies. The time dependence of the ac conductivity at 1 kHz performed at different annealing temperatures, 75, 80, 85 and 90 °C, was used to calculate Avrami exponent. The frequency factor was determined from the temperature dependence of the rate constant.

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

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.

Investigation on glass-forming ability,Flexural strength and microwave dielectric properties of Al2O3-doped LMZBS glasses

In this work, a new high flexural strength microwave dielectric material for LTCC applications, (1-x) Li2OMgOZnOB2O3SiO2-xAl2O3 (x = 1–10 wt %) (LMZBSA) glass-ceramics, was prepared by conventional solid-state reaction method. The effects of Al2O3-doped Li2OMgOZnOB2O3SiO2 (LMZBS) glass on its glass-forming ability (GFA) and activation energy were investigated by Dietzel, Saad-Paulin methods and Kissinger model, respectively. Comparing the undoped sample with the 10 wt % of Al2O3-doped LMZBS glass the parameters of ΔT and S which characterize the GFA increase by 35% and twice, respectively. Meanwhile, the addition of Al2O3 will reduce the activation energy, making initial crystallization easier. And then the impact of Al2O3 on the phase composition, flexural strength and microwave dielectric properties of LMZBSA glass-ceramics was studied systematically. It shows that the content of Al2O3 has a great influence on the flexural strength of LMZBSA glass-ceramics, and different composition is responsible for its microwave dielectric properties. LMZBSA glass-ceramics with 5 wt % Al2O3 sintered 2 h at 900 °C showed the highest relative density (96.41%) and flexural strength (σ = 190 MPa), optimum microwave dielectric properties (εr = 6.8, Q×f = 12500 GHz, τf = −45 ppm/°C).

Multiresponsive Shape-Stabilized Hexadecyl Acrylate-Grafted Graphene as a Phase Change Material with Enhanced Thermal and Electrical Conductivities.

A phase change material (PCM) essentially making up hexadecyl acrylate-grafted graphene (HDA- g-GN) was fabricated via a solvent-free Diels-Alder (DA) reaction. The novel material exhibits multiresponsive, enhanced thermal and electrical conductivities and valid thermal enthalpy. In addition, the optimum DA reaction conditions were explored. A variety of characterization techniques were used to study the thermal, crystalline, and structural properties of HDA- g-GN. The melting and crystallizing enthalpies of HDA- g-GN were as high as 57 and 55 J/g, respectively. Furthermore, the melting and freezing points of HDA- g-GN were 29.5 and 32.7 °C, respectively. The thermal conductivity of HDA- g-GN reached 3.957 W/(m K), which is well above that of HDA itself and the previously reported PCMs. HDA- g-GN exhibited an excellent electric conductivity of 219 S/m. Compared to HDA, the crystalline activation energy of HDA- g-GN decreased from 397 to 278 kJ/mol (Kissinger model) and 373 to 259 kJ/mol (Ozawa model). Moreover, HDA- g-GN exhibited excellent thermal stability, shape stability, and thermal reliability. More importantly, HDA- g-GN can be employed to realize high-performance light-to-thermal and electron-to-thermal energy conversion and storage, which provides wide application prospects in energy-saving buildings, battery thermal management system, bioimaging, biomedical devices, as well as real-time and time-resolved applications.

Synthesis of Eugenol Bio-based Reactive Epoxy Diluent and Study on the Curing Kinetics and Properties of the Epoxy Resin System

In this study, monoglycidyl silyl etherated eugenol (GSE) was synthesized as reactive epoxy diluent, and the chemical structure of GSE, intermediates, and products were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR). GSE existed as a potential bio-based reactive diluent for petroleum-based epoxy resin. The curing kinetics of EP/HHPA/GSE system was studied by non-isothermal DSC method. The kinetics parameters were calculated by using the Kissinger model, Crane model, Ozawa model, and β-T (temperature-heating rate) extrapolation, respectively. In addition, the effects of GSE on the thermo-mechanical properties and thermal stability of EP/HHPA/GSE systems were studied, indicating that GSE can effectively improve the toughness and thermal decomposition temperature of the epoxy system.

Synthesis, kinetics and thermal stability of napthalenic polyimide silica nanocomposites

In this work synthesis, structural morphology, degradation profile and kinetic parameters of napthalenic polyimide (NPI) silica based nanocomposites have been reported. The NPI matrix were reinforced with modified and unmodified silica particles for comparison. The structure of NPI, organically modified napthalenic polyimide nanocomposites (ONPNC) and napthalenic polyimide nanocomposites (NPNC) were confirmed by FTIR spectroscopy. Morphology of the fabricated NPI-SiO2 nanocomposites was examined by field emission scanning electron microscopy (FE-SEM). The degradation kinetics of the nanocomposites was established by thermogravimetric analyzer (TGA) with variable heating rates (β) of 5, 10 and 15 °C/min were used. The kinetic data were fitted to Flynn-Wall-Ozawa and Kissinger models for calculating the apparent activation energy (Ea). The results indicate that the modified silica has a significant impact upon the calculated kinetic parameters (Ea) values for thermal decomposition of ONPNC. Thermal stability and degradation kinetics suggest that these nanocomposite films could be used as polyelectrolyte membrane in fuel cell devices. The conclusion was drawn based on the results of FTIR, FE-SEM, TGA and degradation kinetics.

Glass transition and crystallization of ZnO-B2O3-SiO2 glass doped with Y2O3

The effect of Y2O3 on the glass transition kinetics, crystallization kinetics, phase separation and crystallization behavior of 60ZnO–30B2O3–10SiO2 glass has been investigated by non-isothermal differential thermal analysis, scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The glass transition activation energies Eg calculated by using both Kissinger and Moynihan model decrease from 668 kJ/mol to 573 kJ/mol for Kissinger model, and 682 kJ/mol to 587 kJ/mol for Moynihan model with the increase of yttrium oxide doping content from 0 to 6 mol%. And the glass crystallization kinetics parameters, crystallization activation energy Ec and Avrami exponent n stands for crystal growth, are also obtained on the basis of several well developed equations. Increase of about 58 kJ/mol in Ec values obtained by different theoretical equations is caused by addition of 6 mol% yttrium oxide into 60ZnO–30B2O3–10SiO2 glass, and the Avrami exponent (n close to 2) suggests that crystal growth in 60ZnO–30B2O3–10SiO2 glass doped with or without yttrium is mainly one-dimensional growth of crystals. The results on the phase separation and crystallization behavior occurred at 893 K and 993 K respectively for base and doped glass, are well consistent with the glass transition and crystallization kinetics results. Hence, addition of yttrium oxide into 60ZnO–30B2O3–10SiO2 glass decrease the glass transition activation energy while increase the crystallization activation energy of glass, thereby the stability of glass structure is improved. Phase separation phenomenon and crystallization behavior occurred at glass surface provide some useful information for preparing glass ceramics with micro- or nano-crystals in surface.

Nonisothermal Crystallization Kinetics of Ethylene Vinyl Alcohol Copolymer with Poly(oxypropylene)diamine Intercalated Montmorrilonite

ABSTRACTFilms of ethylene vinyl alcohol copolymer (EVOH) and EVOH containing poly(oxypropylene)diamine intercalated montmorrilonite were prepared by solution casting. The nanostructures and viscosity were characterized by small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and rheological testing. The nonisothermal crystallization kinetics of the samples were investigated by the Ozawa's and Mo's methods and the crystallization activation energy by Kissinger's model. The SAXS and TEM analysis demonstrated that the nanoplatelets, with an intercalated structure, were dispersed in the EVOH matrix. The rheological tests showed that the incorporation of the modified clay could increase the viscosity of the composite system. The Mo's method more successfully described the nonisothermal ctystallization behavior of neat EVOH and its nanocomposites as compared with the Ozawa's method. Adding the nanoclays had a heterogeneous nucleation effect to accelerate the crystallization of EVOH despite hindering the macromolecular chains movement.

Multistage thermal decomposition in films of cadmium chloride-doped PVA–PVP polymeric blend

Films of cadmium chloride (CdCl2) doped polyvinyl alcohol (PVA)–polyvinyl pyrrolidone (PVP) polymer blend have been studied using thermogravimetry (TG) and differential scanning calorimetry (DSC), for doping levels ranging from 0.0 mass% to 50.5 mass%. At high doping levels (beyond 10.2 mass%), TG scans of these films showed several stages of decomposition at temperatures beyond 100 °C, indicating that the incorporation of CdCl2 results in deterioration of PVA–PVP blend, on thermal activation. The presence of melting peaks, which is due to melting of crystalline regions in CdCl2-doped PVA–PVP blend samples and the occurrence of thermal decomposition, in different stages, is confirmed by DSC curves. There is a decrease in decomposition temperature of the doped PVA–PVP blend, with an increase in salt (CdCl2) concentration. Kinetic analysis has been performed using iso-conversional models, using Flynn–Wall–Ozawa (FWO) equation, Kissinger–Akahira–Sunose (KAS) equation and Kissinger relation at four different stages of thermal decomposition, for the 10.2 mass% CdCl2-doped PVA–PVP blend. The higher values of activation energy, Ea= 197.5, 196.0 and 175.3 kJ mol−1 obtained from FWO, KAS and Kissinger models reveal that CdCl2-doped PVA–PVP sample has more thermal stability when compared to the undoped PVA–PVP blend.

Crystallization kinetics study of dynamically vulcanized PA6/NBR/HNTs nanocomposites by nonisothermal differential scanning calorimetry

ABSTRACTInvestigation of crystallization behavior and kinetics of thermoplastic elastomer nanocomposites was the subject of limited works because of complexities associated with semiexperimental modeling of such phenomenon in a system containing components having completely different behavior in the molten state. Nonisothermal crystallization kinetics of dynamically vulcanized PA6/NBR/HNTs thermoplastic elastomer nanocomposites was mathematically modeled applying well‐known Avrami, Ozawa, and Mo theoretical models to the differential scanning calorimetry data gathered at various cooling rates. It was found that HNTs contribute as nucleating agents to the crystallization kinetics and cause acceleration of crystallization. Activation energy of the crystallization was calculated by correlating the crystallization peak temperature with the cooling rate using Kissinger model. It was found that Mo equation could properly describe nonisothermal crystallization kinetics of the PA6/NBR/HNTs thermoplastic elastomer nanocomposites. This was recognized from the obtained parameters of Mo equation in terms of HNTs loading level, which suggested a higher rate for dynamic crystallization. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46488.

High performance epoxy nanocomposite adhesive: Effect of nanofillers on adhesive strength, curing and degradation kinetics

In the current study, the synergistic effect of a multi-walled carbon nanotube (MWCNT) and a nanoclay (C30B) on the mechanical, morphological and thermal behaviour of an epoxy based adhesive was investigated. The adhesive strength was investigated by conducting lap shear tests and from the test results it was observed that, Ep/1.0 C30B adhesive possessed the highest adhesive strength among all the adhesive formulations investigated and showed a 52% enhancement as compared to the pristine epoxy. Fracture analysis of different adhesive systems was investigated using scanning electron microscopy (SEM). SEM micrographs revealed that nanomaterials with different shapes and dimensions provide distinct features on the fracture surfaces due to the different energy dissipation mechanisms which they promote. The morphological variations of the epoxy based nanocomposite adhesives were investigated using transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The curing kinetics of the different nanofiller reinforced epoxy adhesives were examined using a non-isothermal differential scanning calorimetric (DSC) technique. The activation energy (Ea) was calculated by applying Kissinger's method and found to be increased for the Ep/1.0 CNT/1.0 C30B adhesive system as compared to the pristine epoxy. This increment can be attributed to the physical impediment impacted by the nanomaterials on the curing reaction of the epoxy resin. The degradation kinetics of the adhesive systems were also studied using thermogravimetric analysis (TGA). The corresponding activation energies (E) of the adhesive systems obtained by Kissinger's model were found to increase with addition of nanofillers, thus indicating improved thermal stability.

Separation and kinetic analysis of the thermo-oxidative reactions of polyacrylonitrile upon heat treatment

A polyacrylonitrile (PAN) homopolymer and a copolymer with methyl acrylate were analyzed by differential scanning calorimetry (DSC) in order to establish a method for the kinetic analysis of the stabilization reaction steps during heat treatment. The application of a program rarely used for the study of the chemical transformation of PAN and its copolymers resulted in five separate steps, which can be assigned with large probability to various cyclization and oxidation reactions. A more exact identification of the reactions needs further measurements and considerations. Overlapping peaks appearing in the DSC traces were deconvoluted and then quantitatively analyzed to obtain kinetic parameters. The kinetics of the processes were described by the Kissinger model. The model could be fitted well to four of the five processes that may indicate that these belong to individual reactions of the first order. The parameters obtained agree well with the few values of similar investigations published in the literature up to now. The results have large practical relevance, since the kinetic parameters obtained can be used in the preparation of intermediates and for the optimization of the stabilization process.