Flynn Wall Ozawa Method Research Articles

Effect of fullerene (C70) on the structural, morphological optical and thermal properties of poly(butyl methacrylate) (PBMA)

Poly(butyl methacrylate) (PBMA)/Fullerene (C70) nanocomposites were successfully prepared by solvent removal method and characterized by different techniques. Structural characterization showed an interaction between PBMA and C70 nanofiller. Morphological features showed that C70 was homogeneously distributed in the PBMA matrix. Optical analysis confirmed the formation of nanocomposites with wavelength shift in PBMA/C70 nanocomposites compared to pure PBMA. Photoluminescence spectra showed that the emission bands of PBMA/C70 nanocomposites shifted from blue to red and the presence of new emission spectra in the red region. The data obtained from thermal analysis showed that the Tg of the nanocomposites increased by about 10 °C compared to pure PBMA and the maximum decomposition temperatures improved by about 65–70 °C, confirming the increased thermal stability. The data obtained from thermogravimetric analyses performed at different heating rates were analyzed by Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) equations to calculate the activation energy values. According to the regression coefficient values, the experimental results were in good agreement with the FWO method (R2 PBMA=0.937 and R2 PBMA/C70 (5 wt%)=0.953). The activation energy of PBMA and fullerene doped nanocomposite were calculated as 48 kJ/mol and 104 kJ/mol, respectively and the results showed that the Ea value of nanocomposite was higher than PBMA.

Kinetic analysis of coal oxidative pyrolysis before and after immersion effect

The oxidative pyrolysis kinetics of coal before and after immersion effect was studied by thermogravimetric experiments. Non-isothermal thermogravimetric analysis data were analyzed at four heating rates of 5, 10, 20 and 30 K/min. Furthermore, temperature-programmed experiments and Fourier-transform infrared (FTIR) spectroscopy were employed to understand the oxidation activity and chemical structure of raw coal and soaked coal. After coal immersion effect, the increase in the content of active functional groups, the increase in the concentration of gaseous products, and the decrease in crossing point temperature during oxidation process all indicate that soaked coal is easier to oxidize and spontaneously combust. Lastly, four model-free methods such as Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Friedman and Kissinger methods are employed to calculate the activation energy (Eα). Kinetic analysis reveals that Eα value obtained by the former three methods significantly depends on the conversion of coal oxidative pyrolysis process, and the average Eα value of soaked coal obtained by four methods is lower than that of raw coal. For the kinetic analysis of coal oxygen adsorption and combustion stages, it is more reliable to adopt the FWO and KAS methods in turn. This research helps to better understand the mechanism of enhanced oxidation activity of soaked coal and optimizes the calculation method of kinetic parameters in different oxidation stages of coal.

Study on Thermal Oxygen Aging Characteristics and Degradation Kinetics of PMR350 Resin.

The thermal stability and aging kinetics of polyimides have garnered significant research attention. As a newly developed class of high thermal stability polyimide, the thermal aging characteristics and degradation kinetics of phenylene-capped polyimide prepolymer (PMR350) have not yet been reported. In this article, the thermo-oxidative stability of PMR350 was investigated systematically. The thermal degradation kinetics of PMR350 resin under different atmospheres were also analyzed using the Flynn-Wall-Ozawa method, the Kissinger-Akahira-Sunose method, and the Friedman method. Thermogravimetric analysis (TGA) results revealed that the 5% thermal decomposition temperature (Td5%) of PMR350 in a nitrogen atmosphere was 29 °C higher than that in air, and the maximum thermal degradation rate was 0.0025%/°C, which is only one-seventh of that observed in air. Isothermal oxidative aging results indicated that the weight loss rate of PMR350 and the time-dependence relationship follow a first-order exponential growth function. PMR350 resin thermal decomposition reaction under air atmosphere includes one stage, with a degradation activation energy of approximately 57 kJ/mol. The reaction model g(α) fits the F2 model, and the integral form is given by g(α) = 1/(1 - α). In contrast, the thermal decomposition reaction under a nitrogen atmosphere consists of two stages, with degradation activation energies of 240 kJ/mol and 200 kJ/mol, respectively. The reaction models g(α) correspond to the A2 and D3 models, with the integral forms represented as g(α) = [-ln(1 - α)]2 and g(α) = [1 - (1 - α)1/3]2 due to the oxygen accelerating thermal degradation from multiple perspectives. Moreover, PMR350 resin maintained high hardness and modulus even after thermal aging at 350 °C for 300 h. The results indicate that the resin exhibits excellent resistance to thermal and oxygen aging. This study represents the first systematic analysis of the thermal stability characteristics of PMR350 resin, offering essential theoretical insights and data support for understanding the mechanisms of thermal stability modification in PMR350 and its engineering applications.

Investigation of thermal properties and structural characterization of novel boron-containing Schiff base polymers

Three novel Schiff base polymers were synthesized by using the Schiff base monomer obtained using aldehyde containing boric acid and amines containing hydroxyl groups as the starting materials. The polymers were synthesized at the same temperature and using the same amount of oxidizing agent by the oxidative polycondensation method. The characterization of all polymers and monomers was achieved by using Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–vis), nuclear magnetic resonance spectroscopy (1H-NMR), liquid chromatography-mass spectrometry (LC–MS), gel permeation chromatography (GPC) and scanning electron microscopy (SEM). The thermal stability of these compounds was studied by employing thermogravimetric analysis (TGA), and thermodynamics parameters such as activation energy (Ea), enthalpy (∆H), entropy (∆S), and Gibbs free energy(∆G) for the decomposition process were calculated using the Flynn–Wall–Ozawa method.

Pyrolysis of metal oxides treated Canarium schweinfurthii Shell: Investigation of thermogravimetric kinetics and thermodynamics

Metal oxides as catalysts alter the properties of the pyrolysis vapor secondary reactions during the thermal decomposition of several biomass leading to high-value bio-oils. This study aimed to investigate the thermal decomposition characteristics of Canarium Schweinfurthii (CS) shells that were treated with various metal oxides (ZnO, CuO, Fe2O3/FeO, and Fe2O3) using pyrolysis. The study also sought to identify pyrolysis reaction parameters (kinetics and thermodynamics parameters) that are not widely documented. Thermogravimetric pyrolysis was carried out at different heating rates, and the undocumented pyrolysis kinetic parameters were determined using the Flynn-Wall Ozawa method (FWO) according to American Standard Testing and Materials (ASTM) 6441 guidelines for assessing biomass decomposition. The metal oxide-treated CS shells lost significant weight between 62 and 67 wt% during the thermogravimetric pyrolysis, lower than 75 wt% of the CS shell. The average activation energies (Eα) for pyrolysis of the ZnO, CuO, Fe2O3/FeO, and Fe2O3 treated CS shells were 203.04, 155.35, 338.85, and 219.92 kJ/mol, respectively in contrast to that of the untreated CS-shell. The Bayesian Information Criteria revealed that the diffusion kinetics of the Gistling-Brounshtein model best describes the pyrolysis of the shell mixed with metal oxides. The metal oxides affected the CS shells' pyrolysis kinetic parameter (Eα), which can promote pyrolysis vapor upgrading to encourage the widespread use of metal oxides in pyrolysis for bioenergy and chemical recovery.

Pyrolysis behavior of densified refuse-derived fuels (d-RDFs) via TGA: Investigating the impact of densification degree on thermal kinetics and thermodynamics

The conversion of municipal solid waste (MSW) into its energy-rich fraction, known as refuse derived fuel (RDF), addresses both MSW management and energy demand. RDF comprises a diverse blend of various non-hazardous waste streams, making it challenging to predict physical properties and chemical compositions. However, densification can help overcome these challenges. This work aims to explore the effect of densification degree on kinetic and thermodynamic parameters during the degradation of densified refuse-derived fuels (d-RDFs) in inert atmosphere. Herein, three d-RDFs samples obtained with varying degree of densification and die temperatures ranging from 55 °C to 118 °C, as well as a mixed fines (MF) sample produced during the pelletization process, were analyzed. Pyrolysis potential of d-RDFs and MF were determined using thermogravimetric analysis in the temperature range from 30 to 800 °C, at multiple heating rates of 5, 10, and 20 K min−1. The effect of the degree of densification on physical characteristics, and kinetic and thermodynamic parameters of d-RDF was investigated. Apparent activation energy (Eα) was estimated employing Friedman (FR), Kissinger-Akahera-Sunnose (KAS), and Flynn-Wall-Ozawa (FWO) methods. Derived Eα values were used to determine the pre-exponential factor (Aα) using the Kissinger method. Experimental results revealed that the durability of d-RDFs increased from 79.26 % to 98.73 % as the densification degree increased from II to IX. Furthermore, the Eα values exhibited a decreasing trend in the first peaks of the DTG profiles, while an opposite trend was observed in the second peaks of DTG curves. However, with an increase in the degree of densification, the mean values of Eα decreased by 5–10 % for all methods. The Aα values, assessed using the FR method, surpassed the critical value of (109 s−1) for all samples. However, with the KAS and FWO methods, these values fell below (109 s−1) within the conversion range of 0.05–0.25. Thermodynamic parameters confirmed the endothermicity of the thermal degradation process.

A kinetics study of microwave pyrolysis of sewage sludge and corn stalk mixture

AbstractFast pyrolysis of sewage sludge (SS), corn stalk (CS), and their mixture under both direct and indirect microwave heating was carried out in a prototype microwave thermogravimetric reactor at high heating rates, 179 and 203 K/min, respectively. It was found that the samples could be heated up rapidly by direct microwave heating, while there is a temperature lag of the sample to the heated reactor wall in indirect heating. The Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods were used to analyze the thermogravimetric data of SS, CS, and their mixture under direct microwave heating. When the FWO method was used, the average activation energies of SS, CS, and their mixture were obtained as 6.0, 18.9, and 39.8 kJ/mol, respectively. When the KAS method was used, the average activation energies of CS and mixture were 12.6 and 31.6 kJ/mol, respectively. Those values are much lower than reported under conventional heating, and likely result from the interaction of microwave irradiation and the biomass samples. The reaction kinetics of directly microwave‐heated biomass pyrolysis from this study provide essential data for modelling, scaling, and designing the microwave‐assisted in‐situ catalytic pyrolysis reactors with mixed biomass and catalyst particles.

Thermal and calorimetric investigations of some vegetative fuels

AbstractBushfires pose a significant threat to numerous countries, often causing vast property damages and loss of lives. Efforts to combat and manage these fires heavily rely on predicting the fires' rate of spread and intensity. A significant component of these predictions involves understanding the thermophysical characteristics of vegetative fuels. The accuracy of predictive models (especially physical models) also depends on obtaining precise thermophysical and combustion parameters. This research aims to provide a comprehensive set of thermal degradation and combustion parameters for surface and near‐surface fuel samples collected during prescribed fire experiment conducted in April 2022 in Little Desert National Park, Victoria, Australia. Firstly, fuel properties like fuel height, moisture content, bulk density, fuel load and heat of combustion were meticulously characterized for both surface and near‐surface samples. Then activation energies for degradation reactions were determined using the Flynn–Wall–Ozawa method and for the determination of pre‐exponential factors, in most cases these reactions closely aligned with a Second order model. This was followed by determination of other parameters such as heat of reaction, specific heat and conductivity. It was found that the density, activation energy and heat of combustion did not vary significantly across the six samples under question. The comprehensive set of obtained parameters will likely help to facilitate better predictions in fire propagation modelling.

Comprehensive investigation of almond shells pyrolysis using advance predictive models

This research focused on comprehensive characterization and assessment of almond shells pyrolysis for bioenergy potential through thermogravimetric analysis from ambient temperature to 900 °C at different heating rates of 10, 15, and 20 °C/min in inert environment. Iso-conversional model-free methods like Friedman, Ozawa-Flynn-Wall (OFW), and Kissinger-Akahira-Sunose (KAS) were used for kinetic analysis. Average activation energies (Ea) evaluated using Friedman, OFW, and KAS methods were 198.45 kJ mol−1, 204.43 kJ mol−1, and 204.97 kJ mol−1, respectively. The evaluation of thermodynamic parameters, including ΔH‡, ΔG‡, and ΔS‡, was also assessed. The average values of ΔH‡, ΔG‡, and ΔS‡, were found to be 199.4 kJ mol−1, 172.17 kJ mol−1 and 42.60 kJ mol−1 respectively. The reaction mechanism was obtained from combined kinetics. A high R2 value of 0.9933 demonstrates strong agreement between the combined kinetic analysis results and the experimental data. The distribution activation energy model was assessed employing four pseudo elements identified as PC1, PC2, PC3, and PC4. Artificial Neural Network (ANN) and Boosting regression trees (BRT) were used for the prediction of Ea of almond shells pyrolysis. The detailed understanding of thermokinetics and creating customized predictive and innovative modelling techniques like ANN and BRT sets a new benchmark for developing customized models for thermochemical conversion of varieties of almond shells.

Porous‐structured vermiculite/polybutylene adipate terephthalate composite films: The morphology, mechanical properties, and nonisothermal degradation kinetics

AbstractTo examine the impact of vermiculite (VMT) on the environmental and physical aspects of polybutylene terephthalate (PBAT), the thermal degradation behavior of VMT/polybutylene terephthalate polyadipate (VMT/PBAT) composite films was investigated by using the thermogravimetric analysis (TGA). To ensure precise calculation of the specific activation energy values of VMT/PBAT composite films in thermal degradation performance experiments, the Kissinger method (K‐method) and Flynn–Wall–Ozawa method (FWO method) were utilized. Additionally, the reaction mechanism was analyzed using the Coats–Redfern equation (CR equation). The introduction of VMT into the PBAT co‐polyester structure leads to an increase in the thermal degradation activation energy Ek of composite films.; the apparent activation energies were calculated by the Coats–Redfern method for different reaction mechanisms, and the interfacial diffusion reaction mechanism of the composite film was determined, with a thermal degradation reaction principle properties of g(α) = [1 − (1 − α)]2 and the number of reaction steps of 2.Highlights VMT/PBAT composite films prepared using a simple method. Analyzing nonisothermal degradation kinetics using K‐method and FWO method. Analyzing the degradation mechanisms using the Coats–Redfern equation. Addition of VMT enhances the thermal degradation properties of composite films. Addition of VMT reduces the mechanical properties of the composite film.

Co-combustion characteristics and kinetics of sludge/coal blends in 21%–50% oxygen-enriched O2/CO2 atmospheres

This research investigated the thermogravimetric analysis (TGA) and combustion kinetics of sewage sludge and Australian sub-bituminous coal and their blends with different mixing ratios (sludge/coal = 100/0, 80/20, 50/50, 20/80, 0/100 by weight) under air atmosphere (O2/N2 = 21/79 by volume), oxy-fuel combustion (O2/CO2 = 21/79, 25/75, 35/65, and 50/50 by volume), and pyrolysis (pure N2 atmospheres). The gaseous products that evolved from the TGA experiments were also analyzed using a Fourier transform infrared (FTIR) spectrometer under pyrolysis conditions. Results showed that the mixed fuel with higher coal blending ratio had higher ignition temperature, lower burnout temperature and larger combustion characteristic index. Furthermore, TGA–FTIR experiments of the 20 % sludge + 80 % coal blended fuel under nitrogen atmospheres showed more gasification components in pure coal than in sludge. The combustion kinetics analytical results via the Flynn–Wall–Ozawa method indicated that the larger the conversion degree, the smaller the obtained activation energy value. Under the oxy-fuel combustion conditions, when the oxygen concentration increased from 21 % to 50 % for the 20 % sludge + 80 % coal blended fuel, the ignition and burnout temperatures decreased, and the combustion characteristic index increased nearly three times. Oxygen enrichment can clearly improve combustion characteristics and flammability.

Research on the characteristics of pressured pyrolysis products of marine plastics

The problem of marine plastic pollution, mainly composed of polyolefin plastics, is becoming increasingly serious, and reducing marine plastic pollution is urgent. Pyrolysis, as a promising technology for treating polyolefin plastics such as polystyrene (PS), has great potential in addressing marine plastic pollution issues. In order to explore the possibility of resource utilization of marine plastics, this article studied the effect of pressure changes on the pyrolysis products of marine plastics. Marine PS was prepared by soaking routine PS in artificial seawater and air drying, and the most significant difference between the two was found to be the salt attached to the surface. The dynamic characteristics of marine PS were analyzed using Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods, and the apparent activation energy of marine PS calculated by FWO and KAS methods are 102.94 kJ·mol−1 and 95.76 kJ·mol−1, respectively. The effect of pressure at different temperatures on the pyrolysis products of marine PS was studied. The results indicate that the yield of pyrolysis oil decreases as the pressure is increased, while solid products are obtained from scratch. The increase in pressure will gradually make the composition of the thermolytic gas become monotonous. Under critical pressure, pressurization promotes an increase in CH4 content while reducing H2 content, causing the lower heating value of pyrolysis gas to increase to 4.355 kJ·g−1. Analysis of oil content found that increasing pressure promotes the growth of Benzene Toluene Ethylbenzene & Xylene (BTEX) to 33.61%, but excessive pressure can significantly reduce the higher heating value from 42.116 MJ·kg−1 to 31.825 MJ·kg−1. The solid products were characterized using FTIR and it was found that pressure did not have a significant impact on surface functional groups. Increasing the pressure properly promotes the agglomeration of amorphous carbon.

Thermal degradation kinetics, thermodynamics and pyrolysis behaviour of polycarbonate by TGA and Py-GC/MS

This paper elucidates the thermal and catalytic (mordenite and y-zeolite) pyrolysis characteristics of Polycarbonate (PC) as well the kinetics and thermodynamic parameters of the thermal decomposition of PC. Three distinct isoconversional methods, namely the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starkin methods, were employed to evaluate the kinetic and thermodynamic parameters. The average activation energies determined with the KAS, FWO, and Starink methods were 245.81, 235.36, and 249.99 kJ/mol respectively, and they were reduced by 17 % and 21 % when mordenite and y-zeolite were utilized as catalysts, respectively, according to the calculations performed with the KAS method. Py-GC/MS analyses showed that phenolic components were found to be dominant in the oil product obtained under non-catalytic conditions. Micropores in the structure of y-zeolite constitute 54.4 % of the total surface area, while micropores in the structure of mordenite constitute 95.5 % of the total surface area. Depending on the structure of the catalysts used, phenolic components decreased slightly, and aromatic and PAH (Polycyclic Aromatic Hydrocarbons) components replaced these components. As a result, phenolic compounds in the oil product obtained with y-zeolite (56.7 %) were less than those produced with mordenite (61.02 %). PAHs were 12.9 % and 7.5 % in the presence of y-zeolite and mordenite, respectively. Thus, the results evidence the molecular size of zeolite catalysts, as well as their acidic structure, which are crucial factors in the conversion of phenolic compounds.

Effect of sludge-based suppression materials on the explosive flame characteristics of aluminium dust

A study was conducted to investigate the inhibitory effect of sludge-based phosphate-containing composite powder explosion suppressants (MPP/AMS) on aluminium dust explosion and combustion. The experiment compared the inhibition characteristics of ordinary sewage sludge particles, high-temperature alkali-modified sludge particles, phosphate-containing particles, and phosphate-modified sludge particles. The study utilized a flame propagation experimental device and an explosion pressure testing device for comprehensive research. The experimental recording devices revealed that sludge-based composite powder explosion suppressants effectively inhibit aluminium powder explosion and combustion. Thermodynamic analysis of the rapid oxidation stage was performed using the Coats Redfern (C-R) method, and validation was conducted using the Flynn Wall Ozawa (FWO) and Kissinger Akahira Sunose (KAS) methods. The results theoretically explain that sludge-based composite powder explosion suppressants can effectively suppress aluminium powder explosions and exhibit a blocking effect. Surface morphology and material element characterization experiments were conducted before and after the explosion, combined with pyrolysis characteristics. The analysis demonstrated that the inhibition mechanism of sludge-based composite powder explosion suppressants on aluminium powder explosion primarily involves two aspects: physical inhibition (MPP coating inhibition, porous adsorption isolation) and chemical inhibition (decomposition heat absorption, product oxidation). The theoretical findings provide evidence of the superior inhibitory effects of sludge-based composite powder explosion suppressants, offering new insights for the resource utilization of sludge waste and the development of novel explosion suppression materials.

Pyrolysis of combustible fractions in excavated waste: Effect of landfill time on pyrolysis characteristics analyzed by TG-FTIR-MS

Excavated waste in landfills contains non-negligible amounts of combustible fractions, whose mining and thermochemical treatment are promising to save land occupation and achieve energy utilization. Considering the possible changes of combustible fractions in the excavated waste during landfill time, this study comprehensively analyzed the impact of landfill time on the thermogravity characteristics, pyrolysis kinetics, products composition, and pyrolysis pathways of excavated waste using TG-FTIR-MS. The findings indicated a positive correlation between landfill time and the remaining mass resulting from pyrolysis. The activation energies for pyrolysis of excavated waste were found to be greater than those of fresh waste. Specifically, the activation energy values increased from 230.49 kJ/mol to 289.11 kJ/mol for polyethylene, from 216.38 kJ/mol to 260.91 kJ/mol for polypropylene, from 219.04 kJ/mol to 240.06 kJ/mol for expanded polystyrene, and from 210.01 kJ/mol to 279.93 kJ/mol for polyethylene terephthalate, respectively. The increment of activation energies indicates an elevated level of difficulty in the pyrolysis reaction. The pyrolysis kinetics of excavated waste were examined by the Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Starink methods. It was found that FWO method showed an optimal fitting result (R2 =0.9681–0.9819), while KAS and Starink methods also showed satisfactory fitting performance. The TG-FTIR-MS results revealed that the effect of landfill time on products categories are negligible, but the change in the content of pyrolysis products is more pronounced. This study is hoped to provide fundamental insights into the thermochemical disposal and energy recovery of excavated waste in landfills.

Study on the combustion characteristics and kinetics of water hyacinth co-combustion with anthracite

Water hyacinth(WH) is a promising resource produced as a by-product of treating pollution in watersheds, but little study has been done on its high-value applications. In this work, the combustion characteristics of WH, anthracite (AN), and their blends under different ratios, and heating rates were investigated by the thermogravimetric (TG) analyzer. The Kissen-Akahira-Sunose (KAS) and Flynn-WallOzawa (FWO) methods are used to calculate the dynamics, and the interaction between the mixed materials is discussed. The results show that the combustion characteristics of WH are better than those of AN because of its higher volatile components. With the increase of WH, the comprehensive combustion index increased from 0.15(pure AN) to 2.22(WH: AN=5:5). With the increase in heating rate, there is no significant difference in residual. The difference in thermogravimetric curves of mixed fuel in the volatile combustion stage and fixed carbon combustion stage shows that there is an interaction between WH and AN in the process of co-combustion, indicating that the mixed fuel is suitable for co-combustion. This study provides a theoretical basis for improving the efficiency of clean energy and reducing the consumption of fossil energy.

Preparation of Chiral Epoxy Resins and the Optically Active Cured Products

Chirality is one of the most common and significant phenomenon in nature, and epoxy resin is one of the most widely used and researched thermosetting resins, however the influences of chiral carbon in epoxy group on the performances of the cured epoxy resins have ever been hardly studied, therefore it is crucial and meaningful to explore the structure–function relationship of chirality and performance of epoxy resins. Herein, from the analysis of synthesis mechanism, the different chiral configuration with high percent enantiomeric excess (>99%) and racemic bisphenol A epoxy resins were simply prepared by controlling the chirality of epichlorohydrin. The apparent activation energy of the curing process with D230 was calculated by Kissinger method and Flynn–Wall–Ozawa method, respectively, and both results indicate that chirality have no effect on the curing reaction. We found that the secondary structure of epoxy monomer is untouched by its chirality, and they are all right helix structure. For this reason, the thermal stability, glass transition temperature, and thermomechanical properties of diverse chiral epoxy resins cured by D230 have no significant difference. Nevertheless, it was found that the optical rotation activity of chiral epoxy resins can be partially maintained after curing reaction, it manifests the cured products of chiral epoxy resins possesses the possibility of application in the field of polarized materials.

Mechanical properties and curing kinetics of bio-based benzoxazine–epoxy copolymer for dental fiber post

Biocopolymers based on vanillin/fufurylamine–biobenzoxazine (V-fa) and epoxide castor oil (ECO), a bioepoxy, were prepared for application as dental fiber-reinforced composite post. The mechanical and thermal properties of the V-fa/ECO biocopolymers were assessed with regard to the influence of ECO content. The addition of the ECO at an amount of 20% by weight into the poly(V-fa) preserved the stiffness, glass transition temperature and thermal stability nearly to the poly(V-fa). Differential scanning calorimetry (DSC) was used to examine the curing kinetics of the V-fa/ECO monomer system with different heating rates. To determine the activation energy (Ea), the experimental data were subjected to the isoconversional methods, namely Flynn–Wall–Ozawa (FWO) and Friedman (FR). The V-fa/ECO monomer mixture showed average Ea values of 105 kJ/mol and 94 kJ/mol. The results derived using the curing reaction model and the experimental data were in good agreement, demonstrating the efficacy of the FWO method for determining the curing kinetics parameters. The simulated mechanical response to external applied loads by finite-element analysis of the tooth model restored with glass fiber-reinforced V-fa/ECO biocopolymer post showed a similar stress field to the tooth model restored with a commercial glass fiber post. Therefore, based on the findings in this work, it is evident that the bio-based benzoxazine/epoxy copolymer possesses a great potential to be used for dental fiber post.Graphical

Pyrolysis of Aloe vera leaf wastes for biochar production: Kinetics and thermodynamics analysis

The large waste potential of biomass, which is used extensively industrially, is a problem that needs to be solved both environmentally and economically. In this context, the conversion of these wastes into valuable solid products by thermochemical conversion processes is considered a very important alternative. In this study, it was aimed to examine the pyrolytic behavior of Aloe vera leaf waste, determine the pyrolysis kinetic parameters and characterize the biochar obtained as a result of pyrolysis at different temperatures. The pyrolytic behavior of this waste at temperatures between 25 and 600 °C and heating rates of 5, 10, 20 and 40 °C min−1 were investigated by thermogravimetric method. The pyrolysis kinetic parameters of these wastes were calculated using the Kissinger-Akahira-Sunosa (KAS) and Flynn-Wall-Ozawa (FWO) methods. According to the results obtained, the pyrolysis of Aloe vera waste took place in 3 stages (moisture removal, devolatilization and char formation) and approximately 65% of the mass was removed from the structure. The activation energy values calculated by KAS and FWO methods for the devolatilization and char formation stages were found to be approximately 185 kJ mol−1 and 335 kJ mol−1, respectively. According to the kinetic and characterization results obtained, it has been understood that Aloe vera leaf wastes are a very suitable source for biochar production and biochar obtained can be evaluated in different areas such as adsorption, agriculture and combustion.

Insights into Pyrolysis Kinetics, Thermodynamics, and the Reaction Mechanism of Wheat Straw for Its Resource Utilization

To realize the energy recovery of wheat straw, the pyrolysis behavior of wheat straw was studied at three heating rates (10, 20, and 30 K/min) based on thermogravimetric analysis (TG–DTG). Kinetics and thermodynamics were analyzed using Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) model-free methods, and the reaction mechanism was determined using the Coats–Redfern (CR) model-fitting method. The results show that there are three weightlessness stages in the pyrolysis process, of which the second stage was the main weightlessness stage and two distinct peaks of weightlessness were observed in this stage. With increasing heating rate, the main pyrolytic weightlessness peaks of the DTG curve shift to the high-temperature side. The pyrolysis activation energies calculated by the FWO and KAS methods are 165.17–440.02 kJ/mol and 163.72–452.07 kJ/mol, and the pre-exponential factors vary in the range of 2.58 × 1012–7.45 × 1036 s−1 and 1.91 × 1012–8.66 × 1037 s−1, respectively. The thermodynamic parameters indicate that wheat straw has favorable conditions for product formation and it is a promising feedstock. Its pyrolysis reaction was nonspontaneous and the energy output is stable. CR method analysis shows that the A1/3 random nucleation model is the most suitable mechanism to characterize the pyrolysis process and random nucleation may be in charge of the main pyrolysis stage. This study can provide a theoretical basis for the thermochemical conversion and utilization of wheat straw.