General treatment of the thermogravimetry of polymers
01 Nov 1966-Journal of Research of the National Bureau of Standards Section A: Physics and Chemistry (National Institute of Standards and Technology (NIST))-Iss: 6, pp 487-523
TL;DR: It is concluded that methods involving a variable rate of heating or involving several thermogravimetric traces at different rates of heating are capable of establishing the uniqueness of kinetic parameters.
Abstract: Theoretical equations are developed for typical decompositions of polymers including those in which the volatilization does not follow a simple "reaction order" and those made up of a composite of several reactions of differing energies of activation. The effects of order, activation energy, heating rate and temperature dependence upon the calculated thermograms is illustrated. The literature on thermogravimetric kinetics is critically reviewed and coalesced into a logical and coherent development stressing the interrelation of methods and employing a consistent system of notation. As a result, a number of improved methods and new methods for the analysis of kinetic data applicable to the complex systems mentioned above are developed. It is concluded that methods involving a variable rate of heating or involving several thermogravimetric traces at different rates of heating are capable of establishing the uniqueness of kinetic parameters. A new method of determining initial parameters from rate-conversion data is developed. A novel concept is employed of programming reaction variables (in this case, the heating rate) in a manner which greatly simplifies the mathematics of the kinetic system and which shows promise of a wide range of applicability in the area of rate processes.
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TL;DR: In this article, the authors have developed recommendations for reliable evaluation of kinetic parameters (the activation energy, the preexponential factor, and the reaction model) from the data obtained by means of thermal analysis methods such as TGA, differential scanning calorimetry (DSC), and differential thermal analysis (DTA).
4,112 citations
Cites background from "General treatment of the thermograv..."
...7) takes the form also known as the Ozawa [19], and/or Flynn and Wall [20] equation:...
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TL;DR: In this article, two methods of obtaining kinetic parameters from derivative thermoanalytical curves are proposed based on the general form of kinetic formulae and are applicable to general types of reactions governed by a single activation energy.
Abstract: Two methods of obtaining kinetic parameters from derivative thermoanalytical curves are proposed The methods are based on the general form of kinetic formulae and are applicable to general types of reactions governed by a single activation energy One method utilizes the linear relation between peak temperature and heating rate in order to estimate the activation energy, and only the information of the rate of conversion versus the temperature is necessary The other method needs the information of both the conversion and the rate of conversion versus the temperature, and the Arrhenius plot is made for an assumed kinetic mechanism
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TL;DR: A critical review of kinetic models and mathematical approximations currently employed in solid state thermal analysis is provided and analysis of thermal decomposition data obtained from two agricultural residues, nutshells and sugarcane bagasse reveals the inherent difficulty and risks involved in modeling heterogeneous reaction systems.
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TL;DR: Isoconversional analysis of polymer kinetics has been studied extensively over the past decade as discussed by the authors and has been applied to a wide range of applications, including thermal degradation, crosslinking, glass transition, and glass and melt crystallization.
Abstract: Summary: Isoconversional kinetic analysis involves evaluating a dependence of the effective activation energy on conversion or temperature and using this dependence for making kinetic predictions and for exploring the mechanisms of thermally stimulated processes. The paper discusses major results obtained by the authors in the area of the isoconversional analysis of polymer kinetics over the past decade. It provides a brief introduction to isoconversional methods and surveys the impact made by isoconversional analysis in several application areas that include kinetic predictions, thermal degradation, crosslinking (curing), glass transition, and glass and melt crystallization. It is concluded that isoconversional analysis has been used broadly and fruitfully because it presents a fortunate compromise between the single-step Arrhenius kinetic treatments and the prevalent occurrence of processes whose kinetics are multi-step and/or non-Arrhenius.
An isoconversional method applies the Arrhenius equation to a narrow temperature region, ΔT related to a given extent of conversion.
942 citations
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01 Jan 1960
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"General treatment of the thermograv..." refers background in this paper
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