Non-isothermal Thermogravimetry Research Articles

Modulation of Solid-state Thermal Reaction of Iron(III)Citrate by a Co-precursor Studied using Thermogravimetry: Evaluation of Kinetic and Thermodynamic Parameters and Nucleation Rate

Background: Solid state reaction of iron(III)citrate leads to a range of ironbased oxides by varying the reaction conditions, e.g., the presence of co-precursor. The influence of reaction conditions on the kinetics of the solid-state reaction of iron(III)citrate needs to be investigated. Objective: Kinetic analysis of the solid-state reaction of iron(III)citrate in the presence of a co-precursor has been explored to realize the influences of the co-precursor on the reaction process as well as decomposed material. Method:: Non-isothermal thermogravimetry profiles are deconvoluted to individual reaction steps. The model-free kinetic methodology is utilized to estimate step-wise activation energy and, hence, the reaction mechanism along with the reaction rate. Conversiondependent thermodynamic parameters and nucleation rate are estimated. XRD analysis has been used to characterize the decomposed material. Results: Thermogravimetry profiles obtained for an iron(III)citrate and malonic acid mixture are deconvoluted into six steps. The decomposed nanomaterial is identified as magnetite (size 10 nm). The observed reaction mechanisms associated with each step are different, where the activation/reaction rate is conversion-dependent. A good fit between the experimental and reverse-constructed conversion profiles is obtained. The nucleation rate at higher temperatures is affected by both the extent of conversion and the heating rate. A possible reaction pathway is proposed. The study elucidates the role of malonic acid as a co-precursor in modifying the thermal reaction of iron(III)citrate and product formation. Conclusion: This investigation proposes the applicability of suitable co-precursors as a potential controlling factor for preparing iron oxides from iron-based compounds.

Thermal decomposition of active pharmaceutical substances and accuracy of the related kinetic predictions: The case of nifedipine

Non-isothermal thermogravimetry was used to study the thermal decomposition of the nifedipine drug. The dominant process of thermal molecular degradation (as confirmed by Raman spectroscopy) starts very slowly at ∼ 150 °C, which is below the melting point of Tm ≈ 170 °C. The decomposition kinetics was described in terms of the autocatalytic Šesták-Berggren kinetics; a novel approach denoted as single-curve multivariate kinetic analysis (sc-MKA) was used to determine the following set of parameters: activation energy of decomposition Ed = 115.5 ± 2.4 kJ mol-1, decomposition pre-exponential factor log(Ad/s-1) ≈ 8.5–8.9, Šesták-Berggren kinetic exponents M ≈ 0–0.2 and N ≈ 0.3–0.5. The consequent kinetic predictions based on these results have confirmed the good thermal stability of nifedipine, which allows for the melt-quenching preparation of the amorphous phase as well as for the processing via hot melt extrusion and 3D printing. An in-depth analysis of the relevant performance of the sc-MKA approach was done based on the akin literature data for indomethacin, nimesulide, and griseofulvin. The comparison has revealed more than sufficient performance of the sc-MKA method with regard to its application to the thermal decomposition data of active pharmaceutical substances. The most critical aspect of the sc-MKA procedure was demonstrated to be the accurate determination of the model-free parameters (activation energy Ed and pre-exponential factor Ad) and their temperature trends. Considering the specificity of the sc-MKA method, i.e., the fixed value of Ed(T), the determination of the temperature dependence of Ad(T) is of utmost importance and worth extensive repeatability checks.

The Effect of Hollow Glass Microspheres on the Kinetics of Oxidation of Poly(ε-Caprolactone) Determined from Non-Isothermal Thermogravimetry and Chemiluminescence

The effect of hollow glass beads on poly(ε-caprolactone) (PCL) oxidative degradation has been evaluated by the non-isothermal chemiluminescence (CL) method and thermogravimetry analysis (TGA). The main goal of the research and this publication was to reduce the production costs associated with the materials for 3D printing, which would also have a low mass, excellent biocompatibility and suitable thermal properties. Experiments have clearly shown the dual effect of a filler and its extent in terms of poly(ε-caprolactone). The chosen methods demonstrate the superposition of both the pro-degradation and stabilization effects of hollow glass beads on the polymer. The former was evident above the load of 10 wt.% of filler. The non-isothermal TGA records were analyzed as being composed of three temperature-dependent processes of the first-order kinetics. A massive compensation effect between the so-called activation energy and the logarithm of pre-exponential factors for heating rates of 2.5, 5 and 10 °C/min has been shown to be typical for similar non-isothermal thermogravimetry evaluation.

Thermal transformation of 1-(ferrocenyl)ethanol to iron oxide nanoparticles based on reaction atmosphere: analysis of the decomposition reaction using non-isothermal thermogravimetry

Thermal transformation of 1-(ferrocenyl)ethanol to iron oxide nanoparticles based on reaction atmosphere: analysis of the decomposition reaction using non-isothermal thermogravimetry

Induction of styrene backbone cracking by functional group removal in cation exchange resins during thermal decomposition: Kinetic analysis and structural evolution

Cation exchange resin (CER) is widely used in chemical production and nuclear power station. However, the thermal degradation and utilization of spent CERs present challenges. For safe and efficient thermal degradation treatment, kinetic analysis using non-isothermal thermogravimetry (TG) was conducted to investigate the oxidation process of CERs under air atmosphere. The study determined that the Avrami-Erofeev (m = 4, f(α) = 4(1-α)[-ln(1-α)]3/4) and Power law model (n = 1/3, f(α) = 3α2/3) were the most appropriate reactions models for the temperature ranges of 300–397.5 °C and 397.5–467.5 °C, respectively. Moreover, the destruction of the sulfonic functional group (-SO3H) and skeleton at different temperature stages were analyzed by FT-IR. The carbon and sulfur elements transformation in gas products and residues were analyzed by combining on-line mass spectrometry and infrared carbon-sulfur analysis. The results reveal that the degradation process of CERs can be divided into four stages: dehydration, functional group degradation, skeleton degradation, and residual carbon oxidation. Functional groups are used as active sites to form reaction cores. Then the skeleton is decomposed by the power law model, which provides a new research idea for the thermal decomposition of polymers. In addition, the study offers insights into advancing polymer heat treatment technologies and for safety evaluation.

Pyrolysis and CO[formula omitted] gasification of barley straw: Effect of particle size distribution and chemical composition

We evaluate how the heterogeneity of the precursor may affect pyrolysis and CO2 gasification behavior aimed at activated carbon applications. Barley straw, ground and classified into five size ranges, is characterized by non-isothermal thermogravimetry tests at various heating rates. Fixed carbon and volatile matter contents decrease with particle size. Also, the finest fraction is enriched in minerals by exogenous contamination and accumulation of silicon-rich leaves. Faster pyrolysis kinetics are found for small sizes, caused by their higher alkali contents and heat-mass transfer rates. Char-CO2 gasification conversion rates show an unexpected behavior, not previously reported. Higher reactivity is found for the finest fraction, decreasing significantly at temperatures beyond 750 °C. The high alkali content of the finest fraction promotes the catalytic effect of minerals on gasification reactivity at lower temperatures, hindering the reaction at higher temperatures by forming low-melting-point potassium silicates. Results help improve pretreatment strategies to enhance activated carbon quality.

Insights into a co-precursor driven solid-state thermal reaction of ferrocene carboxaldehyde leading to hematite nanomaterial: a reaction kinetic study.

Thermal decomposition of a mixture of ferrocene carboxaldehyde and oxalic acid dihydrate in O2 atmosphere produced rod-like hematite nanomaterial. The decomposition reaction was complex as evident from the overlapped multistep reaction steps in the non-isothermal thermogravimetry (TG) profiles obtained in the 300-700 K range. A peak deconvolution method was applied to separate the overlapped reaction steps. The multistep TG profiles were successfully deconvoluted, which showed that the decomposition occurs in six individual steps. However, it was found that only the last three reaction steps were responsible for the production of hematite. To estimate the activation energy values for these thermal reactions, six model-free integral isoconversional methods were used. The activation energy value significantly depends on the extent of conversion in each step; however, the nature of its dependence significantly different for each step. The most probable stepwise reaction mechanism functions for the solid-state reactions were obtained using the master plot method. The reaction mechanism was found to be different for different steps. Utilizing the activation energy and reaction mechanism function, the reaction rates of decomposition for each step were determined. To substantiate the validity of the assumed kinetic models, the experimental conversion curves were compared with the constructed ones, and the agreement was quite reasonable. The conversion-dependent thermodynamic parameters were obtained utilising the estimated kinetic parameters. Role of the co-precursor in the thermal reaction of the precursor was plausibly revealed. The present study describes how the use of a co-precursor significantly enhances the thermal decomposition of the precursor, how hematite nanomaterials can be synthesized from a co-precursor driven solid state reaction at low temperatures, and how the kinetic calculations facilitate the understanding of the solid-state reaction process. This study proposes the use of a suitable combination of precursor and co-precursor for solid-state thermal synthesis of iron-based nanoparticles using organo-iron compounds as precursor and also illustrates the effective application of the thermal analysis technique to understand the decomposition reaction.

Effect of particle size on the kinetics of pure oxygen combustion of coke

Non-isothermal thermogravimetry technique was used to analyze three groups of coke samples (S-ZD, M-ZD, and L-ZD) of varying particle sizes. The effect of particle size on kinetic parameters was studied in a pure oxygen atmosphere. The ignition (Ti), peak (Tp), and burnout (Tf) temperatures and the flammability (C) and combustion characteristic (Sn) indexes were determined by varying the heating rate (β). The activation energy (Eα) was evaluated following the Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods. Ti, Tp, Tf, C, and Sn correlated positively with the increase in β in a pure oxygen atmosphere. The order of ignition was L-ZD > M-ZD > S-ZD, and the Eα values for the S-ZD, M-ZD, and L-ZD samples were 98.49, 98.35, and 95.17 kJ·mol−1 (FWO) and 90.32, 90.92, and 89.25 kJ·mol−1 (KAS), respectively. Particle size exerted little effect on the kinetics of coke combustion.

Effect of Substitution at the Di- and Trivalent Sites of {N[n- C4H9]4]FeIIFeIII[C2O4]3]}∞ on the Nature of Solid State Decomposition Reaction Leading to Various Metal Oxides

Background: Oxalate ligand-based metal complexes have long been used for the thermal synthesis of metal oxides. Polymeric homo/heterometallic oxalate-based molecular materials of the general formula, {A]MIIMIII[C2O4]3]}∞, [A = organic cation, MII/MIII: di/trivalent transition metal ion; C2O4: oxalate ligand] provides a molecular source to prepare metal oxides through solid state thermal decomposition primarily due to the potential to tune the materials’ outcome by adjusting the molecular stoichiometry and composition. Objective: The study aims to explore the effect of mixing at the di- and trivalent metal sites of {N[n-C4H9]4]FeIIFeIII[C2O4]3]}∞ which decomposes to hematite, on the nature of thermal decomposition reaction as well as the nature of the obtained decomposed materials. Methods: Two series of materials {N[n-C4H9]4]FeII 1-xZnII xFeIII[C2O4]3]}∞ and {N[n- C4H9]4]FeIIFeIII 1-xCrIII x[C2O4]3]}∞ were prepared as precursors for non-isothermal thermogravimetry [TG] study. Model-free integral isoconversional method is employed to calculate the activation energy of decomposition, and hence the most probable reaction mechanism, as well as the reaction rate of thermal decomposition, was determined. Based on the kinetic parameters, the important thermodynamic parameters such as the changes of entropy, enthalpy, and Gibbs free energy are estimated for the activated complex formation from the precursors. Powder X-ray diffraction studies were made to identify the decomposed materials. Results: For materials with 0 < x ≤ 1 well-defined two-step and one-step decomposition process were observed for {N[n-C4H9]4]FeII 1-xZnII xFeIII[C2O4]3]}∞ and {N[n- C4H9]4]FeIIFeIII 1-xCrIII x[C2O4]3]}∞, respectively. For each series of materials, a systematic dependence of the activation energy on the extent of conversion indicates a systematic change in the reactivity. The thermal decomposition strongly depends on the extent of mixing at the di- and trivalent sites and proceeds through different reaction mechanisms at different rates. On the decomposition of these series of materials, a range of metal oxides was obtained. Possibly, during such extent of mixing dependent reactions, the reactant particles go through modifications in their reactivity by several factors. Conclusion: Present work may invoke interest in solid state synthesis of different metal oxides under controlled thermal decomposition by identifying the rate controlling the process through reaction kinetics study for better synthesis and manoeuvring.

Insights into the thermal decomposition of organometallic compound ferrocene carboxaldehyde as precursor for hematite nanoparticles synthesis

Abstract The paper deals with the thermal decomposition of organometallic compound ferrocene carboxaldehyde [(C5H4CHO)Fe(C5H5)] in oxidative atmosphere, which leads to pure hematite nanoparticles, studied with non-isothermal thermogravimetry (TG) protocol. Deconvolution method with Fraser-Suzuki fit function is adopted to resolve the complex multistep TG profiles into six different reaction steps. Step-wise reaction kinetic parameters (activation energy, reaction mechanism function, reaction rate) are estimated based on the mathematical analysis of the multi-heating rate TG data primarily following model-free (integral isoconversional) approach and using master-plot method. The estimated kinetic parameters are utilised to reconstruct the conversion plots which successfully resemble the experimentally observed ones. A plausible reaction process leading to hematite on thermal decomposition of ferrocene carboxaldehyde as the end product is discussed. A comparative discussion on the thermal decomposition of two ferrocene derivatives have been made. The novelty of the present work lies in successful deconvolution of complex TG profiles and hence obtaining the step-wise reaction kinetic parameters demonstrating different reaction mechanisms involved in the thermal synthesis of hematite nanoparticles starting from ferrocene carboxaldehyde which have no prior reporting. Further, a satisfactory agreement between the reconstructed and experimental decomposition profiles establishes the correctness of the applied modelling approach as well as the methodology adopted.

Investigation of mitigation of nitric oxide emission characteristics and slagging properties from biomass combustion by the additive of coal gangue

The co-combustion of coal gangue (CG) and biomass was expected to increase the utilization rate of solid waste and compensating for individual feedstock disadvantages. However, the emission of nitric oxide (NO) and ash melting characteristics during this process was of concern, but no relevant study had focused on this. In this work, the combustion behavior of Salix limb(SL)/Wheat straw(WS), CG and biomass-CG blends was studied by non-isothermal thermogravimetry and tube oven method. The results indicated that when CG was mixed into biomass fuel as an additive, the burn-out effect of CG was improved. The NO emissions from the experimental value of 80% SL/WS blend with 20% CG were reduced by 8.9%/10.1% compared to the theoretical value. Moreover, the potassium aluminum silicates with high melting temperatures were formed in the ash of the composite fuel, which reduced the serious slagging phenomenon that has been observed in the biomass combustion process. The composite fuel of 80% biomass (SL/WS) + 20% CG could promote combustion and reduce NO emissions, which was a meaningful method to treat CG to the maximum benefit and reduced the phenomenon of biomass slagging.

Hydrothermal carbonization of forest waste into solid fuel: Mechanism and combustion behavior

The structural characteristics and fuel performance of hydrochars prepared by hydrothermal carbonization (HTC) of forestry waste (FW) were studied. Proximate analysis and ultimate analysis were used to characterize the chemical composition of the samples, scanning electron microscopy and specific surface area analysis were used to characterize the microscopic results of the samples, Fourier transform infrared spectroscopy and Raman spectroscopy were used to characterize the microcrystalline structure, and non-isothermal thermogravimetry was used to characterize the combustion properties of the HTC products. The results show that with the increase of the HTC temperature, the mass yield of hydrochar decreases, and the content of gas products and liquid products increases. With the increase of HTC temperature, the volatile content of hydrochar gradually decreases, and the fixed carbon content gradually increases. The high heating value (HHV) of FW-280 sample is 1.46 times that of the FW. The porosity and specific surface area increase first and then decrease with the increase of the HTC temperature, and reach the maximum value at 240 °C. With the increase of HTC temperature, the IG/IAll value of the sample increased from 0.282 to 0.346, and the order degree of the carbonaceous structure gradually increased. The combustion process of hydrochars can be divided into two stages: volatile matter removal and carbon combustion. FW-280 has better combustion performance due to its higher carbon content and Rmax2 value of 0.002616. Therefore, the comprehensive research on the physicochemical properties and combustion performance of FW hydrochar will facilitate the expansion of the application of FW resources.

Determination of the Thermodynamic Parameters of the Pyrolysis Process of Post-Consumption Thermoplastics by Non-Isothermal Thermogravimetric Analysis.

Currently, the pyrolysis process is an important technology for the final treatment of plastic waste worldwide. For this reason, knowing in detail the chemical process and the thermodynamics that accompany cracking reactions is of utmost importance. The present study aims to determine the thermodynamic parameters of the degradation process of conventional thermoplastics (polystyrene (PS), polyethylene terephthalate (PET), high-density polyethylene (HDPE), polypropylene (PP) and polyvinyl chloride (PVC)) from the study of their chemical kinetics by thermogravimetric analysis (TG). Non-isothermal thermogravimetry was performed at three heating rates from room temperature to 550 °C with an inert nitrogen atmosphere with a flow of 20 mL min−1. Once the TG data is obtained, an analysis is carried out with the isoconversional models of Friedman (FR), Kissinger–Akahira–Sunose (KAS), and Flynn–Wall–Ozawa (FWO) in order to determine the one that best fits the experimental data, and with this, the calculation of the activation energy and the pre-exponential factor is performed. The validation of the model was carried out using the correlation factor, determining that the KAS model is the one that best adjusts for the post-consumer thermoplastic degradation process at the three heating rates. With the use of the kinetic parameters, the variation of the Gibbs free energy is determined in each of the cases, where it is necessary that for structures containing aromatic groups a lower energy is presented, which implies a relative ease of degradation compared to the linear structures.

Oxidation kinetics of magnesium particles determined by isothermal and non-isothermal methods of thermogravimetric analysis

Knowledge of the oxidation kinetics of magnesium (Mg) particles is important for the development of advanced propulsion and power systems based on combustion of metals. However, reports on the high-temperature oxidation of Mg powders in oxygen are contradictory. In the present work, the oxidation of spherical and non-spherical (flakes) Mg particles in O2 flow was investigated using isothermal and non-isothermal thermogravimetry. Three fractions of the spherical powder were tested, with average sizes about 30, 60, and 300 μm. The oxidation of all powders was complete at temperatures lower than the melting point of Mg, 650 °C. The Friedman analysis of non-isothermal and isothermal thermogravimetric (TG) data has shown that the activation energy exhibits only small fluctuations during a large part of the oxidation process, which indicates that the process can be modeled as a single-step reaction. Model-based analysis has shown that the Avrami-Erofeev model of simultaneous nucleation and growth provides the best fit with the experimental isothermal and non-isothermal TG curves. Scanning electron microscopy of the oxidized spherical particles has shown submicron grains, which is consistent with the Avrami-Erofeev model. The Mampel-Delmon analysis of the isothermal TG data has shown that for the 30 and 60 μm particles, the nucleation is relatively slow, leading to the sigmoidal TG curve, described by the three-dimensional Avrami-Erofeev equation. An increase in the particle size decreases the dimension of this equation, and for the 300 μm particles and flakes, the entire process can be considered as a growth of a non-protective oxide layer. The apparent activation energy of Mg oxidation is likely in the range of 200 – 230 kJ/mol, independently of the particle size and shape.

Surface-induced oxidation kinetics and mechanism of oxidation of 2-D carbon fabric in different oxidative environments

Abstract The oxidation kinetics of a 2-D carbon fabric were studied in both an air and a pure oxygen environment. A simple approach using non-isothermal thermogravimetry and differential thermogravimetry was used. The results showed that the non-isothermal oxidation process of the carbon fabric exhibited self-catalytic characteristics in both environments. The oxidation mechanism and kinetic parameters were analyzed with differential and integral models. Evidence indicated that the oxidation process was a surface-induced phenomenon. The oxidation mechanism in oxygen environment was controlled by random nucleation, whereas in the case of air environment it was phase boundary reaction controlled. Different oxidation mechanisms and their correlations with kinetic parameters have been discussed in detail.

Combustion Behavior and Kinetics Analysis of Isothermal Oxidized Oils from Fengcheng Extra-Heavy Oil

The low-temperature oxidation (LTO) of heavy oil is of great significance for the combustion front stability, which directly influences the efficiency and safety of in-situ combustion (ISC). To provide feasible heating by artificial ignition before the implementation of ISC in the Xinjiang Fengcheng (FC) oilfields, this paper investigates the oxidation behavior of FC extra-heavy oil and its isothermal oxidized oils. Firstly, FC extra-heavy oil was subjected to isothermal oxidation experiments conducted utilizing an oxidation reactor, and the physical properties of the gaseous products and oxidized oils were analyzed. The combustion behavior of the FC extra-heavy oil and oxidized oils was then studied by non-isothermal thermogravimetry and differential scanning calorimetry. Subsequently, the Friedman and Ozawa–Flynn–Wall methods were adopted to perform kinetic analysis. Oxygen consumption was always greater than the production of CO and CO2, so oxygen addition reactions were the main pathway in heavy oil LTO. H/C decreased to 8.31% from 20.94% when the oxidation temperature rose from 50 °C to 150 °C, which deepened the oxidation degree. The density and viscosity of 200 °C to 350 °C oxidized oils increased at a slower rate, which may be related to the LTO heat effect. The change law of temperature interval, peak temperature, and mass loss of the oxidized oils had a good correlation with the static oxidation temperature. Compared with other oxidized oils, the peak heat flow and enthalpy of 350 °C oxidized oil increased significantly with high-temperature combustion, and were 42.4 mW/mg and 17.77 kJ/mol, respectively. The activation energy of 350 °C oxidized oil began to decrease obviously around a conversion rate of 0.4, which indicates that it was beneficial to coke deposition with stronger activity. Finally, we came up with LTO reaction mechanisms and put forward a reasonable preheating temperature for the application of ISC in FC oilfields.

Spectroscopic characterization andthermal decomposition kinetics of 1,3-dibutyl-imidazolium bromide synthesized through a solvent-free and one-pot method

Imidazolium-based ionic liquids (ILs), as one of the most popular and investigated classes of ILs owing to their outstanding physicochemical features, find applications in different fields over the last decades. Their thermal stability is of paramount importance for their effective use at elevated temperatures. 1,3-dibutyl-imidazolium bromide ([BBIm][Br] is an interesting IL, which may be employed for different purposes. Nevertheless, its thermal stability and decomposition kinetic are scarce. In the present work, 1,3-dibutyl-imidazolium bromide ([BBIm][Br]) is successfully synthesized through a simple, clean, and efficient solvent-free and one-pot ultrasonic method. Its structure was assessed by DSC, FTIR, Raman spectroscopies, µXRF, one-dimensional (1-D) liquid state 1H, 13C, and 15N NMR. The 2-D NMR analyses thoroughly discussed herein corroborated the structure of the cation as well as the alkyl side chains. Its thermal stability and decomposition kinetic were performed with non-isothermal thermogravimetry analysis at different heating rates. The kinetic triplet was determined using isoconversional kinetic methods. It is revealed that [BBIm][Br] undergoes a single step mass loss in the temperature range of 180–380 °C for which the activation energy is 140 kJ/mol. Furthermore, it is proved that the decomposition mechanism that best represents the experimental data is the nth order (Fn) reaction mechanism.

Effect of CO2-O2 oxidizing atmospheres on the combustion characteristics of metallurgical coke and anthracite

As a novel method for blast furnace ironmaking, CO2 is utilized in the hot blast and the pulverized coal carrier gas. In order to clarify the function mechanism of CO2/O2 oxidizing atmospheres on the metallurgical reaction of metallurgical coke and anthracite, the combustion characteristics of anthracite and coke in CO2/O2 atmosphere were obtained by non-isothermal thermogravimetry. The physical and chemical structural characteristics of anthracite and coke were measured systematically by using X-ray diffraction(XRD), X-ray fluorescence spectrometer (XRF), laser particle size analysis, scanning electron microscopy(SEM) and Raman spectroscopy analysis. The results show that when the proportion of CO2 in the reaction gas increases, the ignition performance and comprehensive combustion performance of anthracite and coke decrease, and higher heating rate is not conducive to the reaction. The ignition performance and the comprehensive combustion performance of the samples rank in the order anthracite > coke. The volume model (VM) and unreacted core model(URCM) were used to fit the experimental data, and the reaction kinetic parameters and combustion reaction mechanism were obtained. The performance of VM model is slightly better than URCM model.

Thermal degradation kinetics of ethyl vanillin crosslinked chitosan/poly(vinyl alcohol) blend films for food packaging applications

The precise knowledge of thermal degradation of polymers appears to be of great importance in order to identify their applications. In the present work ethyl vanillin (EV) cross linked chitosan (CS)/poly(vinyl alcohol) (PVA) (CPEV) blend films of different mass percent were prepared by solvent casting method, and were characterized by using thermogravimetric/derivative thermogravimetric (TG/DrTG), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. Non-isothermal (dynamic) thermogravimetry was used with three different heating rates (β) namely 5.0, 7.5 and 10.0∘Cmin−1 Kinetic parameters such as activation energy (Ea) and pre exponential factor (A) were calculated using Flynn-Wall-Ozawa (FWO) equation, Kissinger-Akahira-Sunose (KAS) equation and Kissinger relation at three different stages of thermal degradation. The improved thermal staCDC100739ility of EV crosslinked blend films could be due to the formation of Schiff base and inter molecular hydrogen bonding. Calculated percentage of crystallinity (X%) results from DSC and XRD data found to be in good agreement with each other. Crystallinity decreased with increase of CS percent in CPEV blend films.

Lifetime predictions of non-ionic and ionic biopolymers: kinetic studies by non-isothermal thermogravimetric analysis

In this paper, films based on sustainable polymers with variable charge have been investigated by non-isothermal thermogravimetry in order to predict their lifetime, which is a key parameter for their potential use in numerous technological and biomedical applications. Specifically, chitosan has been selected as positively charged biopolymer, while alginate has been chosen as negatively charged biopolymer. Among non-ionic polymers, methylcellulose has been investigated. Thermogravimetric measurements at variable heating rates (5, 10, 15 and 20 °C min−1) have been performed for all the polymers to study their degradation kinetics by using isoconversional procedures combined with ‘Master plot’ analyses. Both integral (KAS and Starink methods) and differential (Friedman method) isoconversional procedures have shown that chitosan possesses the highest energetic barrier to decomposition. Based on the Master plot analysis, the decomposition of ionic polymers can be described by the R2 kinetic model (contracted cylindrical geometry), while the degradation of methylcellulose reflects the D2 mechanism (two-dimensional diffusion). The determination of both the decomposition mechanism and the kinetic parameters (activation energy and pre-exponential factor) has been used to determine the decay time functions of the several biopolymers. The obtained insights can be helpful for the development of durable films based on sustainable polymers with variable electrostatic characteristics.Graphical abstract