Advanced isoconversional method

1997 ◽  
Vol 49 (3) ◽  
pp. 1493-1499 ◽  
Author(s):  
S. Vyazovkin
Keyword(s):  
Isoconversional Method ◽  
Advanced Isoconversional Method

scholarly journals Lifetime Prediction Methods for Degradable Polymeric Materials—A Short Review

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4507 ◽  
Author(s):  
Angelika Plota ◽  
Anna Masek
Keyword(s):  
Polymeric Materials ◽  
Short Review ◽  
Isoconversional Method ◽  
Lifetime Prediction ◽  
Accelerated Ageing ◽  
Radiation Chemical ◽  
Degradation Reactions ◽  
Wlf Model ◽  
Advanced Isoconversional Method ◽  
The Impact

The determination of the secure working life of polymeric materials is essential for their successful application in the packaging, medicine, engineering and consumer goods industries. An understanding of the chemical and physical changes in the structure of different polymers when exposed to long-term external factors (e.g., heat, ozone, oxygen, UV radiation, light radiation, chemical substances, water vapour) has provided a model for examining their ultimate lifetime by not only stabilization of the polymer, but also accelerating the degradation reactions. This paper presents an overview of the latest accounts on the impact of the most common environmental factors on the degradation processes of polymeric materials, and some examples of shelf life of rubber products are given. Additionally, the methods of lifetime prediction of degradable polymers using accelerated ageing tests and methods for extrapolation of data from induced thermal degradation are described: the Arrhenius model, time–temperature superposition (TTSP), the Williams–Landel–Ferry (WLF) model and 5 isoconversional approaches: Friedman’s, Ozawa–Flynn–Wall (OFW), the OFW method corrected by N. Sbirrazzuoli et al., the Kissinger–Akahira–Sunose (KAS) algorithm, and the advanced isoconversional method by S. Vyazovkin. Examples of applications in recent years are given.

Influence of carbon nanofillers on the curing kinetics of epoxy-amine resin

RSC Advances ◽  
2015 ◽  
Vol 5 (110) ◽  
pp. 90437-90450 ◽  
Author(s):  
L. Vertuccio ◽  
S. Russo ◽  
M. Raimondo ◽  
K. Lafdi ◽  
L. Guadagno
Keyword(s):  
Activation Energy ◽  
Curing Kinetics ◽  
Isoconversional Method ◽  
Epoxy Amine ◽  
Carbon Nanofillers ◽  
Advanced Isoconversional Method ◽  
Kinetics Of

Variation of the activation energy with conversion obtained by “advanced isoconversional method”.

A new diagnostic when determining the activation energy by the advanced isoconversional method

2016 ◽  
Vol 636 ◽  
pp. 85-93 ◽  
Author(s):  
James S. Campbell ◽  
John R. Grace ◽  
C. Jim Lim ◽  
David W. Mochulski
Keyword(s):  
Activation Energy ◽  
Isoconversional Method ◽  
Advanced Isoconversional Method

scholarly journals Kinetics and Chemorheological Analysis of Cross-Linking Reactions in Humins

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1804 ◽  
Author(s):  
Sangregorio ◽  
Guigo ◽  
Jong ◽  
Sbirrazzuoli
Keyword(s):  
Complex Viscosity ◽  
Isoconversional Method ◽  
Effect Of Temperature ◽  
Diffusion Control ◽  
Model Free ◽  
Platform Chemicals ◽  
Model Free Kinetics ◽  
Acid Catalyzed ◽  
Advanced Isoconversional Method ◽  
Kinetics Of

Humins is a biomass-derived material, co-product of the acid-catalyzed conversion of cellulose and hemicellulose to platform chemicals. This work presents a thorough study concerning the crosslinking kinetics of humins by chemorheological analysis and model-free kinetics under isothermal and non-isothermal curing. Humins can auto-crosslink under the effect of temperature, and the reaction can be fastener when adding an acidic initiator. Thus, the effect of P-Toluenesulfonic acid monohydrate (pTSA) on the crosslinking kinetics was also studied. The dependencies of the effective activation energy (Eα-dependencies) were determined by an advanced isoconversional method and correlated with the variation of complex viscosity during curing. It is shown that humins curing involves multi-step complex reactions and that the use of an acidic initiator allows faster crosslinking at lower temperatures, involving lower Eα. The shift from chemical to diffusion control was also estimated.

scholarly journals Comparative Kinetics Study of the Thermal and Thermo-Oxidative Degradation of a Polystyrene-Clay Nanocompozite by TGA and DSC

2010 ◽  
Vol 5 (2) ◽  
pp. 68-72
Author(s):  
Ion Dranca ◽  
Nicon Ungur ◽  
Tudor Lupascu ◽  
Oleg Petuhov
Keyword(s):  
Activation Energy ◽  
Kinetic Data ◽  
Oxidative Degradation ◽  
Isoconversional Method ◽  
Comparative Assessment ◽  
Kinetics Study ◽  
Scanning Calorimetry ◽  
Advanced Isoconversional Method ◽  
Tga And Dsc ◽  
Thermo Oxidative Degradation

The methods of thermogravimetry (TGA) and differential scanning calorimetry (DSC) have been used to study the thermal and thermo-oxidative degradation of polystyrene (PS) and a PS-clay nanocomposite. An advanced isoconversional method has been applied for kinertic analysis. Introduction of the clay phase increasers the activation energy and affects the total heat of degradation, which suggests a change in the reaction mechanism. The obtained kinetic data permit a comparative assessment of the fire resistance of the studied materials.

scholarly journals Curing Characterisation of Spruce Tannin-based Foams using the Advanced Isoconversional Method

BioResources ◽  
2014 ◽  
Vol 9 (3) ◽  
Author(s):  
Matjaž Čop ◽  
Marie Pierre Laborie ◽  
Antonio Pizzi ◽  
Milan Sernek
Keyword(s):  
Isoconversional Method ◽  
Advanced Isoconversional Method

Development of HPLC Method for the Purity Test by Design of Experiments and Determination of Activation Energy of Hydrolytic Degradation Reactions of Sofosbuvir

2020 ◽  
Vol 16 (7) ◽  
pp. 976-987
Author(s):  
Jakub Petřík ◽  
Jakub Heřt ◽  
Pavel Řezanka ◽  
Filip Vymyslický ◽  
Michal Douša
Keyword(s):  
Activation Energy ◽  
Design Of Experiments ◽  
Mobile Phase ◽  
Hydrolytic Degradation ◽  
Isoconversional Method ◽  
Hplc Method ◽  
Organic Modifier ◽  
Calculation Methods ◽  
Degradation Reactions

Background: The present study was focused on the development of HPLC method for purity testing of sofosbuvir by the Design of Experiments and determination of the activation energy of hydrolytic degradation reactions of sofosbuvir using HPLC based on the kinetics of sofosbuvir degradation. Methods: Following four factors for the Design of Experiments were selected, stationary phase, an organic modifier of the mobile phase, column temperature and pH of the mobile phase. These factors were examined in two or three level experimental design using Modde 11.0 (Umetrics) software. The chromatographic parameters like resolution, USP tailing and discrimination factor were calculated and analysed by partial least squares. The chromatography was performed based on Design of Experiments results with the mobile phase containing ammonium phosphate buffer pH 2.5 and methanol as an organic modifier. Separation was achieved using gradient elution on XBridge BEH C8 at 50 °C and a flow rate of 0.8 mL/min. UV detection was performed at 220 nm. The activation energy of hydrolytic degradation reactions of sofosbuvir was evaluated using two different calculation methods. The first method is based on the slope of dependence of natural logarithm of the rate constant on inverted thermodynamic temperature and the second approach is the isoconversional method. Results and Conclusion: Calculated activation energies were 77.9 ± 1.1 kJ/mol for the first method and 79.5 ± 3.2 kJ/mol for the isoconversional method. The results can be considered to be identical, therefore both calculation methods are suitable for the determination of the activation energy of degradation reactions.

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