Thermal Degradation Kinetics Research Articles

Thermal Degradation Kinetics of Natural Fibers: Determination of the Kinetic Triplet and Lifetime Prediction

Thermal Degradation Kinetics of Natural Fibers: Determination of the Kinetic Triplet and Lifetime Prediction

Slow pyrolysis of Agave americana L. fibers: Analysis of kinetics and thermodynamics using the coats-redfern method at different heating rates

This study employed thermogravimetric analysis (TGA) alongside the Coats-Redfern method (CRM) to investigate the thermal degradation's kinetics and thermodynamics of fibers extracted from the flower stalk of Agave americana (FSAA). We explored FSAA fibers' thermal behavior across varying heating rates (HRs) to elucidate complex reaction mechanisms and estimate critical parameters. TGA experiments at 5, 10, and 20 °C/min HRs reveal a multi-step breakdown process supported by solid coefficients of determination (R2 > 0.99). Activation energy values, ranging from 83.6 to 210.1 kJ/mol, vary with HR, providing insights into thermal decomposition kinetics. Thermodynamic parameters, including variations in entropy (ΔS), Gibb's free energy, and enthalpy, shed light on spontaneity and energy transfer during the process. Negative ΔS values suggested reduced disorder during thermal decomposition. This study represented a novel investigation into the thermal behavior of fibers extracted from the FSAA for the first time, using CRM in conjunction with TGA. Through comprehensive analysis, we elucidated the kinetics and thermodynamics of FSAA fiber degradation across various HRs. Our findings shed light on the intricate reaction mechanisms underlying FSAA fiber decomposition, providing valuable insights for potential applications in biofuel production and composite materials.

Diffusion and Chemical Degradation of Vitamin B6 in Chickpeas (Cicer arietinum L.) during Hydrothermal Treatments: A Kinetic Approach.

Chickpeas are more sustainable than other food systems and have high a nutritional value, especially regarding their vitamin composition. One of the main vitamins in chickpeas is vitamin B6, which is very important for several human metabolic functions. Since chickpeas are consumed after cooking, our goal was to better understand the role of leaching (diffusion) and thermal degradation of vitamin B6 in chickpeas during hydrothermal processing. Kinetics were conducted at four temperatures, ranging from 25 to 85 °C, carried out for 4 h in an excess of water for the diffusion kinetics, or in hermetic bags for the thermal degradation kinetics. Thermal degradation was modeled according to a first-order reaction, and diffusion was modeled according to a modified version of Fick's second law. Diffusivity constants varied from 4.76 × 10-14 m2/s at 25 °C to 2.07 × 10-10 m2/s at 85 °C; the temperature had an impact on both the diffusivity constant and the residual vitamin B6. The kinetic constant ranged from 9.35 × 10-6 at 25 °C to 54.9 × 10-6 s-1 at 85 °C, with a lower impact of the temperature. In conclusion, vitamin B6 is relatively stable to heat degradation; loss is mainly due to diffusion, especially during shorter treatment times.

Pyrolysis of multilayered plastic packets to hydrocarbon fuel feedstock: Thermal degradation behaviour, kinetics and thermodynamic analysis, and semi-batch studies

This study examines the kinetics and batch pyrolysis behavior of multilayered waste milk packets to optimize their conversion into valuable products. Using thermogravimetric analysis at heating rates of 5, 10, 15, and 20 °C/min and employing the model fitting and model-free methods such as the Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Kissinger methods, the process was found to follow an F1 order-based mechanism with an activation energy of 304 kJ/mol and a pre-exponential factor of 2.60 × 1012 min.−1 The maximum weight loss (97.2 %) occurs at 5 °C/min. The average changes in free energy, enthalpy, and entropy are 814.939 kJ/mol, 135.698 kJ/mol, and −903.846 × 10−3 kJK−1mol−1 respectively. At 450 °C, the maximum pyrolytic oil yield reaches 66.92 %, with FTIR analysis confirming the presence of diverse hydrocarbon components such as alkanes, alkenes, cycloalkanes, aromatic hydrocarbons etc. in the oil. Kinetic triplet and thermodynamic parameter data, alongside physical and chemical analyses, suggest that the pyrolytic oil from multilayered waste milk packets could serve as a superior substitute for petrochemical fuel oil.

Studies on thermal degradation kinetics and machine learning modeling of hydrochar produced from hydrothermal carbonization of municipal sewage sludge and key lime peel

Studies on thermal degradation kinetics and machine learning modeling of hydrochar produced from hydrothermal carbonization of municipal sewage sludge and key lime peel

Exploring the structure, characteristics, and thermal degradation of composites comprising thermoplastic polyolefin and graphene oxide under high-temperature dynamic shear conditions

Dynamic high-temperature shear aging tests were conducted on thermoplastic polyolefin (TPO)/graphene oxide (GO) composite materials using a Hakke torque rheometer. The study employed ATR-FTIR, DSC, SEM, oxygen performance testing, and TGA to analyze the structure, properties, thermal degradation behavior, kinetics, and mechanisms of TPO/GO composites. The results demonstrated that the high-temperature dynamic shear thermal oxidative aging of TPO/GO composite materials establishes a dual protective mechanism, incorporating physical (intercalation oxygen resistance) and chemical (inorganic oxygen resistance) effects. This can be attributed to the polar surface and honeycomb structure of GO, as well as the shear-induced more uniform physical distribution of GO within TPO. Consequently, TPO/GO composite materials exhibit significantly enhanced resistance to dynamic shear thermal oxidative aging compared to TPO alone.

Thermal Stability, Durability, and Service Life Estimation of Woven Flax-Carbon Hybrid Polyamide Biocomposites.

Woven flax-carbon hybrid polyamide biocomposites offer a blend of carbon fibers' mechanical strength and flax's environmental advantages, potentially developing material applications. This study investigated their thermal behavior, degradation kinetics, and durability to water uptake and relative humidity exposure and compared them with pure flax and carbon composites with the same matrix. The hybrid composite exhibited intermediate water/moisture absorption levels between pure flax and carbon composites, with 7.2% water absorption and 3.5% moisture absorption. It also displayed comparable thermal degradation resistance to the carbon composite, effectively maintaining its weight up to 300 °C. Further analysis revealed that the hybrid composite exhibited a decomposition energy of 268 kJ/mol, slightly lower than the carbon composite's value of 288.5 kJ/mol, indicating similar thermal stability. Isothermal lifetime estimation, employing the activation energy (Ed) and degree of conversion facilitated by the Model Free Kinetics method, indicated a 41% higher service life of the hybrid laminate at room temperature compared to the carbon laminate. These insights are crucial for understanding the industrial applications of these materials without compromising durability.

Effect of metals and brominated flame retardants on thermal degradation kinetics of waste printed circuit board

Waste printed circuit board (WPCB) is an indispensable component in any waste electrical and electronic equipment (WEEE). A promising method for recycling WPCB is pyrolysis. To understand the effect of metals and brominated flame retardants (BFR) on WPCB pyrolysis, four samples were prepared, namely (a) raw WPCB (RW), (b) non-metallic WPCB (NM), (c) bromine extracted WPCB (RWBFR_ext) and (d) bromine and metal extracted WPCB (NMBFR_ext). The degradation kinetics study using the isoconversional methods: Friedman, Ozawa-Flynn-Wall (OFW), Kissinger–Akahira–Sunose (KAS), and Starink showed that the extraction of metals exhibited an increase in final degradation temperature and activation energy (Eα), and altered the reaction mechanism (f(a)) whereas, the reduction of BFR reduced initial degradation temperature. The identified kinetic triplets were verified using the reconstruction profiles. The parameters can be used in designing applications and developing an energy-efficient pyrolysis process.

Thermal Stability, Crystallization, and Melting Behaviours of Iodine Doped Semiconducting Polyethylene Terephthalate (PET) Thin Films

The influence of iodine doping on the thermal stability, degradation kinetics, and the melting and crystallization behaviors of polyethylene terephthalate (PET) films were investigated. Iodine doping was performed by immersing PET films in 0.4 M I2/l toluene. The thermal stability and degradation kinetics of PET and the semi-conducting PET/iodine complex films were studied using the thermogravimetric analysis-derivative thermogravimetric analysis (TGA-DTGA) studies and the differential scanning calorimetry (DSC). It was found that iodine incorporation accelerated the thermal degradation and weight loss through increased chain mobility owing to the imperfections formed by doping. Both pure and doped films exhibited appreciable thermal stability with the peak degradation temperature above 400 °C. DSC thermograms of the pristine PET and the PET/iodine films in the crystallization regions were recorded during the cooling scan and the significant parameters were studied. The peak crystallization temperature of PET increased from 192 to 209 °C after iodination. Doping initiated crystallization at an early stage of cooling with an increase in the rate of crystallization and smaller crystallization half time. Iodine catalyzed crystallization and acted as a nucleating agent. DSC scans were also used to study the melting characteristics of the polymer samples. The peak melting temperature was lower and the absolute crystallinity reduced for the iodine doped PET films.

Evaluation of the thermal degradation kinetics of vitamin C in the pulp of tumbo (Passiflora mollissima b.)

Vitamin C is an important micronutrient, which is found in acidic fruits such is the case of tumbo, studies have shown beneficial effects of vitamin C on health due to its antioxidant and free radical scavenging capabilities. The objective of the research was to evaluate the thermal degradation kinetics of vitamin C of the pulp of tumbo (Passiflora mollissima b.). The pulp of tumbo was prepared and subsequently subjected to different temperatures (60, 70 and 80 ° C) and times (0, 5, 10, 15 and 20 min). The vitamin C content in the pulp of tumbo was 77.01 mg / 100g which was analyzed by spectrophotometry. The results showed that vitamin Cdegradation followed second-order kinetic models. The degradation rate constants for ascorbic acid in the tumbo pulp were: k60 = 0.014 min-1, k70 = 0.019 min-1 and k80 = 0.023 min-1 and the decimal reduction times are: D60 = 162.17 min, D70 = 121.74 min and D80 = 101.76 min. The z value was 99 ° C, the Ea in the temperature range of 60-80 ° C is 22.84 kJ / mol and the value of Q10 is 1.60. The optimal time and temperature of pasteurization in the pulp of tumbo is 10.69 min at 60 ° C, for presenting the best correlation index, retaining the greatest amount of ascorbic acid, presenting a lower reaction rate and requiring a longer time of decimal reduction. It was concluded that the higher the temperature, the higher the degradation of vitamin C, the data obtained will help to predict the best conditions of processing of the pulp of tumbo and minimize degradation since it is an important quality factor.

An assessment of the role of nanosilica in thermal/thermo‐oxidative degradation mechanism of poly(lactic acid)/polybutylene adipate terephthalate blend nanocomposites

AbstractAs a packaging materials candidate, based on a polylactic acid/ polybutylene adipate terephthalate (PLA/PBAT) blends (90/10 and 75/25 wt/wt) containing 1, 3, and 5 phr hydrophilic (HPL) and hydrophobic (HPB) nanosilica (NS) particles in the presence of a multifunctional epoxide compatibilizer were prepared by melt mixing, in a twin‐screw extruder. Scanning electron microscopic studies confirmed a matrix‐droplet morphology with finer dispersed domains at higher NS content. Energy dispersive spectroscopy mapping also indicated uniform dispersion of NS in blends, with some agglomerates at higher content of nanoparticles. Moreover, transmission electron microscope was applied to study the impact of nanofillers' localization on the systems' morphology. It was observed that NS particles localized at the PLA‐PBAT interface. In addition, thermogravimetric analysis (TGA) was used to investigate thermal stability and thermal degradation kinetics. Data indicates that hydrophobic NS improved thermal stability. The activation energy of degradation was calculated using several techniques of data modeling, including Friedman, Flynn‐Ozawa‐Wall, and Kissinger‐Akahira‐Sunose models. Among blend nanocomposites, 75/25 blend containing 5 phr HPB NS had the maximum degradation activation energy, suggesting that this sample had the most resistance to heat degradation. The intensity of the TGA/FTIR peaks of the evolved products was found to be correlated with the activation energy. The Criado's technique was also used to investigate the changes in the thermal degradation mechanism.

Effect of faujasite zeolites on the thermal stability and degradation kinetics of nitrocellulose

ABSTRACT In the present work, to enhance the thermal stability of nitrocellulose (NC), the effect of inorganic stabilizers, namely, Y-ammonium or Y-hydrogen zeolites, has been investigated. Comparative tests were conducted to assess the physicochemical properties and thermal behavior of the nitrocellulose supplemented with these substances. Various analytical techniques were employed. The obtained results highlighted the exceptional scavenging performance of these inorganic stabilizers. Notably, the NC/Y-ammonium and NC/Y-hydrogen samples exhibited higher retention of NO x , compared to NC/diphenylamine (DPA). The FTIR spectra of the NC/stabilizer systems revealed that the morphology and chemical structure of the conventional NC remained unaltered with the incorporation of 3 wt.% of stabilizer. Moreover, the B&J and VST tests indicated that the stability of the NC/stabilizer blends, specifically those incorporating NC/Y-ammonium and NC/Y-hydrogen zeolites, surpassed that of both pure NC and NC/DPA samples. It is also revealed that Y-ammonium and Y-hydrogen zeolites have a minimal impact on the decomposition temperature of NC (Ea = 137 kJ.mol−1, log (A) > 12.7 s−1), but exhibit a significant increase in the apparent activation energy and pre-exponential factor (Δ Ea > 33–43 kJ.mol−1, Δ log (A) > 2.3–4.9 s−1). These findings highlight promising aspects of utilizing inorganic stabilizers to substitute DPA in the industrial production of energetic materials.

Effect of para-substituent on copolymerization and thermal degradation kinetics of styrene copolymers composed with maleic anhydride derivative

Effect of para-substituent on copolymerization and thermal degradation kinetics of styrene copolymers composed with maleic anhydride derivative

Degradation kinetics of PLA compounds with castor oil

AbstractPoly (lactic acid) (PLA) compounds with castor oil (CO) and epoxidized castor oil (ECO) were produced via formic acid, with levels of 5% CO, 3 and 5% ECO. The contribution of this study lies in the detailed analysis of thermal degradation and degradation kinetics of PLA/CO and PLA/ECO. Chemical changes were evidenced by Fourier transform infrared (FTIR), thermal stability, and degradation kinetics were investigated by thermogravimetric analysis (TGA), using Friedman (FR), Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS) and Vyazovkin (VZ) models. Results showed changes in FTIR spectra for PLA/CO and PLA/ECO. For PLA/5%CO and PLA/3%ECO, lower energy bonds formation were observed, resulting in modifications in the involved molecules and presence of CH type bonds in PLA/5%ECO. TGA analysis showed that PLA presented greater thermal stability compared with PLA/CO and PLA/ECO, with T5% = 306°C. The compounds 5% CO, 3 and 5% ECO exhibited lower degradation temperatures (298, 300, and 296°C), compared with PLA, as well as slower decomposition rates. Kinetic modeling using KAS and OFW models proved to be incapable of describing the degradation kinetics of PLA and its compounds. However, FR and VZ were considered adequate, with discrepancies varying between 7% to −4% and 9% to −3%, which showed higher (215, 185, 210, 189 KJ/mol) at α = 0.3 for PLA.

Synthesis, thermal stability, and degradation kinetics of a novel boron‐containing novolac based on triphenyl borate

AbstractA novel boron‐containing novolac (triphenyl borate‐formaldehyde resin, TPBF) was synthesized. The structure, thermoplasticity, molecular weight, and molecular weight distribution of TPBF have been characterized with FT‐IR, melt viscosity, 13C NMR and GPC. The thermal stability of TPBF was investigated by TGA, indicating the thermal stability of TPBF was much better than that of normal novolac (phenol‐formaldehyde resin, PF). TPBFs with different molar ratios of formaldehyde to benzene ring in triphenyl borate (TPB) were also synthesized and compared for molecular size, polydispersity and thermal stability. Further, the thermal degradation kinetics of TPBFs and PF were studied by TGA using Madhusdanan‐Krishnan‐Ninan method and the activation energies were calculated at different degradation stages. It was found that the thermal degradations of TPBFs and PF are a multistage reaction and the degradation reactions in every stage follow the first order reaction mechanism. Finally, the activation energies of thermal degradations of novolac increase with the introduction of boron, the progress of degradation reaction as well as the increase of molar ratios.

Depolymerization of PMMA-Based Dental Resin Scraps on Different Production Scales

This research explores the depolymerization of waste polymethyl methacrylate (PMMAW) from dental material in fixed bed semi-batch reactors, focusing on three production scales: laboratory, technical and pilot. The study investigates the thermal degradation mechanism and kinetics of PMMAW through thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses, revealing a two-step degradation process. The heat flow during PMMAW decomposition is measured by DSC, providing essential parameters for designing pyrolysis processes. The results demonstrate the potential of DSC for energetic analysis and process design, with attention to standardization challenges. Material balance analysis across the production scales reveals a temperature gradient across the fixed bed negatively impacting liquid yield and methyl methacrylate (MMA) concentration. Reactor load and power load variables are introduced, demonstrating decreased temperature with increased process scale. The study identifies the influence of temperature on MMA concentration in the liquid fraction, emphasizing the importance of controlling temperature for efficient depolymerization. Furthermore, the research highlights the formation of aromatic hydrocarbons from the remaining char, indicating a shift in liquid composition during the depolymerization process. The study concludes that lower temperatures below 450 °C favor liquid fractions rich in MMA, suggesting the benefits of lower temperatures and slower heating rates in semi-batch depolymerization. The findings contribute to a novel approach for analyzing pyrolysis processes, emphasizing reactor design and economic considerations for recycling viability. Future research aims to refine and standardize the analysis and design protocols for pyrolysis and similar processes.

Kinetics Study of PVA Polymer by Model-Free and Model-Fitting Methods Using TGA.

Thermogravimetric Analysis (TGA) serves a pivotal technique for evaluating the thermal behavior of Polyvinyl alcohol (PVA), a polymer extensively utilized in the production of fibers, films, and membranes. This paper targets the kinetics of PVA thermal degradation using high three heating rate range 20, 30, and 40 K min-1. The kinetic study was performed using six model-free methods: Freidman (FR), Flynn-Wall-Qzawa (FWO), Kissinger-Akahira-Sunose (KAS), Starink (STK), Kissinger (K), and Vyazovkin (VY) for the determination of the activation energy (Ea). TGA showed two reaction stages: the main one at 550-750 K and the second with 700-810 K. But only the first step has been considered in calculating Ea. The average activation energy values for the conversion range (0.1-0.7) are between minimum 104 kJ mol-1 by VY to maximum 199 kJ mol-1 by FR. Model-fitting has been applied by combing Coats-Redfern (CR) with the master plot (Criado's) to identify the most convenient reaction mechanism. Ea values gained by the above six models were very similar with the average value of (126 kJ mol-1) by CR. The reaction order models-Second order (F2) was recommended as the best mechanism reaction for PVA pyrolysis. Mechanisms were confirmed by the compensation effect. Finally, (∆H, ∆G, and ∆S) parameters were presented and proved that the reaction is endothermic.

Thermal degradation behavior and kinetics of porous polymer based on high functionality components

AbstractTwo kinds of porous polymer were prepared based on high functionality components. Thermogravimetric analysis (TGA) is used to compare the thermal degradation behavior and kinetics of these two materials. The thermogravimetric tests of rigid polyurethane foam (H‐RPUF) and polyurea aerogel (H‐PUA) were carried out in nitrogen atmosphere at different heating rates. The thermal degradation characteristics of the porous polymer were obtained. The apparent activation energy (Ea) of thermal degradation of the porous polymer was investigated by model‐free methods. The results showed that the thermal degradation temperature and ash content of H‐RPUF were higher than those of H‐PUA, and the volatile content was lower. With the rise of heating rate, thermal hysteresis effect of the two porous polymer was relatively high, while the release amount of volatiles was unchanged. For the Kissinger method, Ea of H‐PUA and H‐RPUF was 212.8 kJ mol−1 and 157.4 kJ mol−1, respectively. According to Starink method, the average activation energy of H‐PUA and H‐RPUF was 220.2 kJ mol−1 and 107.2 kJ mol−1, respectively. Obtained by Flynn‐Wall‐Ozawa model, the average activation energy of H‐PUA and H‐RPUF was 219.0 kJ mol−1 and 111.5 kJ mol−1, respectively. The data obtained from the three models all show that Ea of thermal degradation of H‐PUA is higher than that of H‐RPUF, and it is less likely to decompose.

Effect of beeswax and petroleum wax on the thermal degradation behavior, kinetics, and thermodynamics of low‐grade coal

AbstractThe co‐pyrolysis behavior of low‐grade coal with two different feedstocks (beeswax and petroleum wax) at different compositions (w/w) [(75:25), (50:50), (25:75)] is investigated by using a thermogravimetric (TG) analyzer under the non‐isothermal condition at a constant heating rate of 20°C/min from an ambient temperature to 900°C under nitrogen atmosphere. The kinetic and thermodynamic analysis for the thermal decomposition of the sample parameters was carried out by applying the model fitting Coats–Redfern method to the thermogravimetry data of different feedstocks. The activation energy of thermal degradation of coal is found to be 55.8 kJ/mole. A decrease in activation energy is observed by the addition of 25% and 50% waxes in the blended sample and the blended sample with 25% wax and 75% coal has the lowest activation energy. The activation energy for coal‐beeswax blend (75:25) is 35.718 KJ/mol, but it is 34.237 KJ/mol for coal‐petroleum wax blend (75:25). The value of ∆H decreases by the addition of waxes and follows the order (Coal: Feedstock) {(75:25) < (50:50) < (25:75)}, while that of value of ∆S increases by the addition of waxes and follows the order {(75:25) > (50:50) > (25:75)}. However, the value of ΔG does not significantly shift as the blend ratio of the feedstocks is altered. The addition of both feedstocks with the coal sample showed some degree of synergy. The result illustrates that the co‐pyrolysis of coal with wax be energy economical than individual pyrolysis and this study would give precious scope to design a more efficient conversion system.

Pyrolysis characteristics and kinetic analysis of coconut shell and nutmeg shell for potential source of bioenergy

This study explores the pyrolytic characteristics of coconut shells and nutmeg shells as potential bioenergy sources, addressing a research gap in comparing their energy potential. It employs analytical techniques like Field Emission Scanning Electron Microscopy, Fourier Transform Infrared Analysis, and Thermogravimetric Analysis for surface morphology analysis, volatile compound detection, and pyrolysis process investigation. Using kinetic analysis methods, such as ASTM E2070 - Method A, Friedman, and Vyazovkin, thermodynamic properties like enthalpy, Gibbs free energy, and entropy are determined at a single heating rate. Activation energy, pre-exponential factors, and thermodynamic values are presented for both materials. Coconut shells exhibit higher activation energies, indicating greater thermal stability, especially in ASTM E2070 - A and Friedman methods. In contrast, nutmeg shells have lower activation energies, suggesting simpler decomposition. Thermodynamic evaluations favor coconut shells, highlighting increased disorder during pyrolysis compared to nutmeg shells. These findings offer insights into their thermal degradation kinetics, informing potential applications in pyrolysis processes.