International Confederation For Thermal Analysis And Calorimetry Research Articles

The Status of Pyrolysis Kinetics Studies by Thermal Analysis: Quality Is Not as Good as It Should and Can Readily Be

This paper is a literature survey that focuses on the present development of thermokinetic publications. It demonstrates that in recent years pyrolysis kinetics has turned into a major application of the thermokinetics. Analysis of the respective publications suggests that too often their quality leaves much to be desired because of the poor choices of the kinetic methods and experimental conditions. It is explained that the proper choices can be made by following the recommendations of the International Confederation for Thermal Analysis and Calorimetry (ICTAC). To help with improving the quality of the kinetic results, the ICTAC recommendations are condensed to a few easy to follow principles. These principles focus on selecting proper computational methods, collecting better experimental data, and efficiently reporting the results. The paramount computational principle is to avoid using the methods that evaluate the activation energy and other kinetic parameters from the data measured at a single heating rate. It is shown that the kinetic parameters evaluated by such methods can give rise to striking examples of failure when estimating the thermal stability at ambient temperature. Because of the vital importance of pyrolysis kinetics studies from an ecological and economical perspective, a substantial improvement of their quality is currently needed.

Self-heating evaluation on thermal analysis of polymethyl methacrylate (PMMA) and linear low-density polyethylene (LLDPE)

Thermal analysis has been proven to be an efficiently technique to analyse thermal decomposition reactions of different type of materials. This technique is widely used in different fields. Among them, fire science, where polymeric materials are very common, has a particular issue, being the combustion reactions recurrent on these analyses. Thermal analysis has different particularities depending on the studied material. For instance, polymeric materials could undergo different decomposition reactions that are highly dependent on definition of the thermal analysis boundary conditions. The International Confederation for Thermal Analysis and Calorimetry (ICTAC) (Vyazovkin et al. in Thermochim Acta 590:1–23, 2014) and standards (ISO 11358-1. Plastics—Thermogravimetry (TG) of polymers—Part 1: General principles. ISO. 2014; https://www.iso.org/standard/59710.html. Accessed 31 Jan 2022), (ISO 11357-1. Plastics — Differential scanning calorimetry (DSC) — Part 1: General principles. ISO. 2016; https://www.iso.org/standard/70024.html. Accessed 31 Jan 2022) stablish how to set-up these boundary conditions in the thermogravimetric (TG) and differential scanning calorimetry (DSC) standards. As far as initial amount of sample mass is concern, some discrepancies can be found between the standards. For instance, the standards suggest a sample mass between 10 and 100 mg for TG and between 2 and 40 mg for DSC, whereas the ICTAC recommendations suggests that the sample mass times the heating rate should not exceed 100 mg K·min−1 in thermo-oxidative decomposition analysis, which is equivalent to samples masses lower than 10 mg for heating rates of 10 K·min−1, or lower than 5 mg for heating rates of 20 K·min−1. This discrepancy may lead to obtain different results from the tests. Additionally, according to the thermal and thermo-oxidative decomposition of polymers, the ICTAC remarks the influence on the results of the sample thicknesses, carrier gas and heating rates, but it does not analyse the influence of self-heating as it does for the hazardous materials. This work presents a study of the self-heating influence in the thermal decomposition processes of two widely used polymers as poly methyl methacrylate (PMMA) and linear low-density polyethylene (LLDPE). TG/DSC tests are used to evaluate the thermal decomposition processes. Boundary conditions of the tests definition as sample mass, atmospheres, and heating rate are considered to evaluate its influence on the polymers self-heating effect on the thermal decomposition. It also includes how to check if TG/DSC tests follows the theoretical principles of the thermal analysis, or if the results are affected by the self-heating. In the present study, a series of 32 experimental tests has been performed, analysing 16 boundary conditions. These experimental tests allow evaluating the influence of selected boundary conditions on the mass loss, the heat flux, and the materials decomposition reactions. Additionally, we analyse the effect of the boundary conditions on the temperature of the sample. Results show the impact of each different boundary conditions of the self-heating effect, and its influence in the final thermal decomposition measured and they represent an aid to define the suitable conditions to perform TG/DSC test on PMMA and LLDPE, or similar polymer materials. This is done by the evaluation of the influence of the self-heating in parameters as the sample temperature lags defined in [1], the reactions heat fluxes, and the difference between the sample and the programmed temperature. It is also analysed the influence of the auto-ignition temperature in the thermal analysis. It is remarkable the PMMA auto-ignition temperature effect on the TG/DSC results. Finally, some useful recommendations have been defined.

Advanced parametrisation of phase change materials through kinetic approach

Phase change materials (PCM) have been widely investigated for heat storage and transfer applications. Numerous numerical simulation approaches have been proposed for modelling their behaviour and predicting their performance in thermal applications. However, simulation approaches do not consider the kinetics of the phase transition processes, compromising the accuracy of their predictions. The phase change is a kinetically driven process in which both the reaction rate and the reaction progress depend on the heating schedule. This work evaluates and parametrises the influence of kinetics in the melting and crystallisation behaviour of a well-known PCM, PEG1500, and compares potential discrepancies with common phase change parametrisation alternatives. The kinetic dependence was experimentally evaluated through differential scanning calorimetry (DSC). The kinetic parameters required for modelling the kinetics of the processes were determined by both model-free and model-fitting procedures following ICTAC (International Confederation for Thermal Analysis and Calorimetry) recommendations. Then, the phase transition was parametrised through a kinetic model and compared with three conventional phase transition models: linear without hysteresis, non-linear without hysteresis, and non-linear with hysteresis. The statistical comparison between models demonstrates the higher accuracy of the kinetic approach to correctly represent the partial enthalpy distribution of latent heat storage materials during alternative phase change rates, obtaining a coefficient of determination (R2) of 0.80. On the other hand, the accuracy of kinetic-independent models is limited to the range from 0.40 to 0.61. The results highlight the high discrepancies of conventional models compared to the kinetic approach and provide criteria and guidelines for efficient kinetic modelling of phase change in heat transfer evaluations.

Pretreatment of Automotive Shredder Residues, Their Chemical Characterisation, and Pyrolysis Kinetics

Automotive Shredder Residue (ASR), a waste when metals are mostly removed from end-of-life vehicles, has constituents similar to municipal solid waste (MSW) consisting of plastics, rubber, textiles, and some metals. The processing of ASR is a challenge due to its heterogeneous nature, making feeding to a reactor difficult. In this work, a new procedure of ASR pretreatment is proposed to bring particulate nature in the sample for easier feeding during pyrolysis. The thermal breakdown characteristics of the pretreated ASR solids under slow pyrolysis conditions were assessed in a thermogravimetric analyser following the International Confederation for Thermal Analysis and Calorimetry (ICTAC) kinetics committee recommendations. The effect of particle sizes and heating rates were studied at temperatures up to 800 °C at different heating rates of 2, 5, and 10 °C/min for three particle sizes, 38–63 µm, 63–90 µm, and 90–106 µm, and the kinetic data were derived. The volatiles emitted during pyrolysis were characterized by Diffuse Reflectance Infrared Spectroscopy (DRIFTS). We also developed an algorithm for the selection of heating rate during the pyrolysis of the pretreated ASR. The DRIFTS results, kinetic data, and heating rate for the selected particle sizes are useful for the development of a pyrolysis process for pretreated ASR.

How much is the accuracy of activation energy affected by ignoring thermal inertia?

AbstractThis work estimates the magnitude of the effect of thermal inertia on the value of the activation energy determined from heat‐flux differential scanning calorimetry (DSC) data. The estimates are obtained via analysis of the literature data on crystallization of copper and thermal degradation of isotactic polystyrene (iPS). The copper crystallization data have been obtained for very large masses (200 mg) and fast heating rates up to 80 K min−1. The iPS degradation data have been collected on small masses (3 mg) and at the heating rates up to 20 K min−1. For crystallization of copper, the Kissinger activation energy obtained from the DSC data corrected for thermal inertia is 34% larger than the value estimated from uncorrected data. This difference drops to 8% and becomes statistically insignificant when the fastest heating rate used is decreased to 10 K min−1. For iPS degradation, the difference in the isoconversional activation energies estimated, respectively, from corrected and uncorrected DSC data is less than 3% and is not statistically significant. Overall, the effect of thermal inertia on the activation energy appears negligible provided that DSC measurements are conducted on smaller samples and at slower heating rates, that is, as advised by the International Confederation for Thermal Analysis and Calorimetry (ICTAC) recommendations. It is suggested that the difference in the activation energies should generally be within the typical 5‐10% uncertainty as long as the product of the time constant and the maximum heating rate does not exceed 2‐3 K.

Thermal Response and Degressive Reaction Study of Oxo-Biodegradable Plastic Products Exposed to Various Degradation Media

In this work, three plastic film products commonly used as commodity thermoplastic articles were analysed with the aim of characterizing their thermal behaviour and stability. The test specimens were subjected to a series of analytical tests to confirm their biodegradable nature. The specimens ranged between 30 and 70 μm in thickness and showed high concentrations of regulated metals, namely, lead (Pb), postchemical analysis which can lead to its migration to natural sinks. The specimens were also exposed to degressive media, namely, accelerated (UV induced) weathering and soil burial field testing. The weight loss measured exceeded 58% after soil burial indicating deterioration under natural environmental stressors. In addition, the thermal characterization campaign executed with the aim of determining the product’s thermal response followed internationally recognised experimental protocols for the determination of thermal stability. The methodology used followed the International Confederation for Thermal Analysis and Calorimetry (ICTAC) recommendation for thermal stability and the computation of kinetic parameters. The degradation reaction kinetics were also determined postexposure to degressive media. Thermogravimetric analysis coupled with differential scanning calorimetry heat flow analysis and Fourier infrared spectroscopy results was also used in studying the degradation behaviour of the specimens. Analytical kinetic estimation methods relying on model free solutions enabled the determination of the apparent activation energy (Ea) of the specimens postexposure to degradation media. A shift in the degradation mechanism was also detected after studying the kinetic parameters which showed a range of Ea between 86.64 and 226.90 kJ mol-1 depending on the type of specimens and exposure media. It can be concluded that the oxo-biodegradable films are well suited for thermal treatment in the future as discarded plastic solid waste (PSW) articles. This work also paves the way for developing national standards and future plans for societies burdened with PSW accumulation.

Thermal decomposition of polyimides containing phosphine-oxide units

This work details analyses of the thermal decomposition behaviour of three phosphine-oxide containing aromatic processable polyimides. The polymers exhibited high thermal stability with initial decomposition temperatures in the range of 473–483 °C and a char residue at 900°C in the domain of 48.58–58.38%. The values of non–isothermal decomposition kinetic parameters were determined using the Friedman isoconversional method, as recommended by the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC). The data evidenced a complex decomposition process of the main chain, being probably initiated by the cleavage of the weaker PC bonds, followed by the decomposition of the macromolecular backbone. The volatile products formed during the thermal decomposition of polyimides were analysed by TGA-FTIR. All spectra evidenced peaks associated with water, CO2, CO and aliphatic and aromatic decomposition products predominant from 500° to 800 °C. By using Py-GC–MS studies the fragments originating from the thermal decomposition of the polyimides up to 600 °C were identified. Based on these data, it was suggested that the thermal decomposition pathways of the three polyimides undergoes the same mechanism. Additionally, an oversimplified decomposition mechanism for the polyimides was proposed. The morphology of the char residue obtained after TGA experiments showed a continuous and dense structure. The EDX mapping identified the C, N, O and P atoms uniformly dispersed in the residual char surface.

Thermal Characterization and Model Free Kinetic Application on a Tar Sand Sample

In the first part of this research, kinetic software was developed for the evaluation of kinetic parameters using nonisothermal thermogravimetry data. Different computational methods were used and applied to a set of experimental and simulated data distributed in the ICTAC (International Confederation for Thermal Analysis and Calorimetry) kinetics project. The reliability of the software was verified by comparing the kinetic results and it was observed that the results were in good agreement. In the second part, developed software was applied to determine the kinetics of a tar sand sample. Therefore, experiments were performed at three different heating rates, in the temperature range of 20–900°C. Different stages of mass loss regions were observed in TG-DTG curves. Ozawa-Flynn-Wall (OFW), Kissinger, and Augis-Bennett kinetic models were used to determine the activation energy of tar sand sample and the results are discussed.

ICTAC Kinetics Committee recommendations for collecting experimental thermal analysis data for kinetic computations

The present recommendations have been developed by the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC). The recommendations offer guidance for obtaining kinetic data that are adequate to the actual kinetics of various processes, including thermal decomposition of inorganic solids; thermal and thermo-oxidative degradation of polymers and organics; reactions of solids with gases; polymerization and crosslinking; crystallization of polymers and inorganics; hazardous processes. The recommendations focus on kinetic measurements performed by means of thermal analysis methods such as thermogravimetry (TG) or thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and differential thermal analysis (DTA). The objective of these recommendations is to assist a non-expert with collecting adequate kinetic data by properly selecting the samples and measurement conditions.

Thermal Decomposition Study of Ferrocene [(C5H5)2Fe

A single-step thermal decomposition of ferrocene [(C5H5)2Fe] using nonisothermal thermogravimetry (TG) has been studied using single- as well as multiple-heating rate programs. Both mechanistic and nonmechanistic methods have been used to analyze the TG data to estimate the kinetic parameters for the solid state reaction. Two different isoconversional methods (improved iterative method and model-free method) have been employed to analyze the TG results to find out whether the activation energy of the reaction depends on the extent of decomposition and to predict the most probable reaction mechanism of thermal decomposition as well. A comparison of the activation energy values for the single-step thermal reaction of ferrocene estimated by different methods has been made in this work. An appraisal on the applicability of single-heating rate data for the analysis of single-step thermal decompositions over the recommendations by the International Confederation for Thermal Analysis and Calorimetry (ICTAC) is made to look beyond the choice.

TG–DSC analysis of pyrolysis process of two Chinese oil shales

According to the recommendations developed by the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC), non-isothermal pyrolysis experiments were carried out to analyze and compare two types of oil shale from the northeast of China using simultaneous differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis at temperatures ranging from 40 to 850 °C. The pyrolysis process of oil shale begins with the evaporation of small molecular substances, then continues by the pyrolysis of kerogen, and finally ends mainly with the complete decomposition of carbonates. In this whole process, almost 36 % of overall pyrolytic heat was used for the pyrolysis of kerogen. When retorting air-dried basis oil shale below 520 °C, a considerable proportion of the heat required will have to be used mainly for the evaporation of small molecular substances below 185 °C. Specific heat capacities of two oil shale semicokes were measured below 500 °C by DSC method, showing that specific heat capacity of semicoke will increase with the increase of the temperature, and carbonization of kerogen can bring about a further positive effect on it. Coats–Redfern method was used to calculate kinetic parameters in three pyrolysis stages.

New Regional Editor

Andrei Rotaru was born on the 9th of August 1983 in Craiova, Romania. Since November 2006, he is working at the National Institute for Laser, Plasma and Radiation Physics (INFLPR) Bucharest, Romania, where he currently holds the position of Researcher III (equiv. to Lecturer). Andrei has received his BSc in Chemistry and Physics from the Faculty of Chemistry of the University of Bucharest in 2006, specializing in Physical chemistry. Since 2004, he has carried out research in the field of thermal analysis and kinetics of heterogeneous processes (decomposition of various systems, including liquid crystals and dyes, complex inorganic materials and precursors, biomass and coal). He has also developed a software for performing kinetic computations (TKS-SP) and later on used this knowledge in studying, modelling and processing of thin films by laser-assisted techniques (mainly MAPLE). In 2007, Andrei has received an EPSRC grant, followed by a prestigious fellowship of the Roberto Rocca ‘‘Educational Program’’ for his doctoral studies in solid-state chemistry of ceramic materials at the University of St Andrews, United Kingdom. These more recent interests are related to the fabrication, thermal processing and characterization of novel electroceramic materials with tetragonal tungsten bronze structure. In general, a special interest was directed on modelling relaxation processes in polar dielectric ceramics and investigating the structure–properties relations to induce and control ferroelectricity and ferromagnetism. In 2011, he was the co-chairman of the 1st Central and East European Conference on Thermal Analysis and Calorimetry (CEEC-TAC1), and in 2008 a member of the scientific committee of the 14th International Congress on Thermal Analysis and Calorimetry (ICTAC14) in Brazil; he is a member of the International Confederation for Thermal Analysis and Calorimetry (ICTAC), Commission for Thermal Analysis and Calorimetry of the Romanian Academy (CATCAR), Kinetics committee at ICTAC, International Society for Optics and Photonics (SPIE), and president of the Central and Eastern European Committee for Thermal Analysis and Calorimetry (CEEC-TAC). Currently, he acts as an editor for thermal analysis at the Global Journal of Analytical Chemistry and as a reviewer for several journals: The Journal of Physical Chemistry, Journal of Thermal Analysis and Calorimetry, Thermochimica Acta, Journal of Applied Polymer Science, Dyes & Pigments, Chemical Industry & Chemical Engineering Quarterly, etc. Andrei has been an invited lecturer at several universities and institutes from Lithuania, Estonia, Slovakia, Czech Republic, Poland, and is directly involved and interested in A. Rotaru (&) INFLPR – National Institute for Laser, Plasma and Radiation Physics, Bvd. Atomistilor, nr 409, Magurele (Ilfov), Bucharest, Romania e-mail: andrei.rotaru@inflpr.ro Name: A. Rotaru

New Associate Editor

Jiri Malek received his M.Eng. and Ph.D. degrees from Department of General and Inorganic Chemistry, Institute of Chemical Technology Pardubice in 1982 and 1986 specializing in thermal behavior of non-crystalline materials. He is currently professor of Physical Chemistry at University of Pardubice, where he has been teaching Calorimetry and Thermal analysis at the undergraduated and postgraduate levels. He spent two years as a visiting researcher at the National Institute for Materials Science, Tsukuba, Japan, two years at the University of Sevilla, and one year at the University of Catalunya, Spain. His research interests cover kinetics of solid-state processes, nucleation-growth processes in amorphous materials, structural relaxation and visco-elastic behavior of noncrystalline materials, and highly supercooled glass-forming liquids, nanostructured oxidic materials, and phase change materials, with more than 110 papers published. In 2000, he was awarded D.Sc. degree from the Institute of Chemical Technology in Prague. He is a fellow of Engineering Academy of the Czech Republic (EACR), member of the scientific board of the Czech Science Foundation (CSF), and member of the Council of International Confederation for Thermal Analysis and Calorimetry (ICTAC).

Report on the ICTAC Kinetics Committee (August 1992 to September 1994)

This report is a summary of the proceedings at the two most recent workshops of the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC), held at the 10th ICTAC Congress, University of Hertfordshire, UK on 28 August 1992 and at the 6th European Symposium on Thermal Analysis and Calorimetry (ESTAC), Grado, Italy on 13 September 1994. It includes the proceedings of a workshop on the kinetics of dehydration of a proposed lithium sulfate monohydrate standard, reports on the present status of Kinetics Committee working projects, and a summary of the discussion at a workshop on “New Directions for Thermal Analysis Chemical Kinetics”.