scholarly journals All You Need to Know about the Kinetics of Thermally Stimulated Reactions Occurring on Cooling

Molecules ◽  
2019 ◽  
Vol 24 (10) ◽  
pp. 1918
Author(s):  
Tatsiana Liavitskaya ◽  
Sergey Vyazovkin
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Kinetic Studies ◽  
Isoconversional Method ◽  
Single Step ◽  
Scanning Calorimetry ◽  
Practical Advice ◽  
Heating And Cooling ◽  
Theoretical Considerations ◽  
Kinetics Of

In this tutorial overview article the authors share their original experience in studying the kinetics of thermally stimulated reactions under the conditions of continuous cooling. It is stressed that the kinetics measured on heating is similar to that measured on cooling only for single-step reactions. For multi-step reactions the respective kinetics can differ dramatically. The application of an isoconversional method to thermogravimetry (TGA) or differential scanning calorimetry (DSC) data allows one to recognize multi-step kinetics in the form of the activation energy that varies with conversion. Authors’ argument is supported by theoretical considerations as well as by experimental examples that include the reactions of thermal decomposition and crosslinking polymerization (curing). The observed differences in the kinetics measured on heating and cooling ultimately manifest themselves in the Arrhenius plots of the opposite curvatures, which means that the heating kinetics cannot be used to predict the kinetics on cooling. The article provides important background knowledge necessary for conducting successful kinetic studies on cooling. It includes a practical advice on optimizing the parameters of cooling experiments as well as on proper usage of kinetic methods for analysis of obtained data.

Study on Curing Kinetics of MEP-15/593/660 System

2014 ◽  
Vol 988 ◽  
pp. 31-35
Author(s):  
Jia Le Song ◽  
Chan Chan Li ◽  
Zhi Mi Zhou ◽  
Chao Qiang Ye ◽  
Wei Guang Li
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Kinetic Parameters ◽  
Curing Kinetics ◽  
Conversion Ratio ◽  
Scanning Calorimetry ◽  
Degree Of Cure ◽  
Curing Kinetic ◽  
The Relationship ◽  
Kinetics Of

Curing kinetics of MEP-15/593 system and MEP-15/593/660 system is studied by means of differential scanning calorimetry (DSC). Curing kinetic parameters are evaluated and the relationship between diluent 660 and the curing properties is investigated. The results show that the diluent 660 can not only reduce viscosity and activation energy, but also improve the degree of cure and conversion ratio.

Study on the β1→α+β2 Transformation Kinetics of Ti-6Al-4V Alloy by DSC

2014 ◽  
Vol 508 ◽  
pp. 110-113
Author(s):  
Rong Hua Zhang ◽  
Biao Wu ◽  
Xiao Ping Zheng
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Phase Transformation ◽  
Cooling Rate ◽  
Volume Fraction ◽  
Avrami Exponent ◽  
Transformation Kinetics ◽  
Cooling Process ◽  
Scanning Calorimetry ◽  
Kinetics Of

The temperature and duration of β1→α+β2 transformation of Ti-6Al-4V alloy in cooling process were measured by differential scanning calorimetry, and transformation activation energy and Avrami exponent of β1→α+β2 were also calculated. The results show that the cooling rate is in the range of 在5～20°C/min, the transformation temperature and the transformation duration β1→α+β2 transformation of Ti-6Al-4V alloy decreased with the increasing cooling rate, its transformation activation energy decreased with the increasing phase transformation volume fraction, and Avrami exponent was between 1 and 2 at 660°C.

Non—Isothermal Differential Scanning Calorimetry Studies on Nanocrystallization Kinetics of Fe81Si3.5B13.5C2 Amorphous Alloy

2011 ◽  
Vol 688 ◽  
pp. 180-185
Author(s):  
Yu Zhang ◽  
Wei Lu ◽  
Biao Yan ◽  
Yu Xin Wang ◽  
Ying Yang
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Amorphous Alloy ◽  
Three Dimensional ◽  
Crystallization Mechanism ◽  
Scanning Calorimetry ◽  
Average Value ◽  
Initial Stage ◽  
Friedman Method ◽  
Kinetics Of

The nanocrystallization kinetics of the Fe81Si3.5B13.5C2amorphous alloy was investigated by differential scanning calorimetry (DSC). The apparent activation energy Ea, as well as the nucleation and growth kinetic parameters has been calculated by Kissinger and Ozawa methods. The changeable activation energy Eawith crystalline fraction α was obtained by the expended Friedman method without assuming the kinetic model function, and the average value of Eawas 364±20 kJ/mol. It was shown that the crystallization mechanism of initial stage (0<α<0.7) of the transformation was bulk crystallization with two and three dimensional nucleation graining growth which was controlled by diffusion. For the middle stage (0.7<α<0.9), the crystallization mechanism is surface crystallization with one dimensional nucleation graining growth at a near-zero nucleation rate. In the final stage(α>0.9)，the local Avrami exponents rose anomalously from 1.4 to about 2.0.

scholarly journals Kissinger Method in Kinetics of Materials: Things to Beware and Be Aware of

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2813 ◽  
Author(s):  
Sergey Vyazovkin
Keyword(s):  
Activation Energy ◽  
Isoconversional Methods ◽  
Single Step ◽  
Order Reaction ◽  
Kissinger Method ◽  
Scanning Calorimetry ◽  
First Order ◽  
Kinetics Of ◽  
Final Equation ◽  
Derivative Thermogravimetry

The Kissinger method is an overwhelmingly popular way of estimating the activation energy of thermally stimulated processes studied by differential scanning calorimetry (DSC), differential thermal analysis (DTA), and derivative thermogravimetry (DTG). The simplicity of its use is offset considerably by the number of problems that result from underlying assumptions. The assumption of a first-order reaction introduces a certain evaluation error that may become very large when applying temperature programs other than linear heating. The assumption of heating is embedded in the final equation that makes the method inapplicable to any data obtained on cooling. The method yields a single activation energy in agreement with the assumption of single-step kinetics that creates a problem with the majority of applications. This is illustrated by applying the Kissinger method to some chemical reactions, crystallization, glass transition, and melting. In the cases when the isoconversional activation energy varies significantly, the Kissinger plots tend to be almost perfectly linear that means the method fails to detect the inherent complexity of the processes. It is stressed that the Kissinger method is never the best choice when one is looking for insights into the processes kinetics. Comparably simple isoconversional methods offer an insightful alternative.

Crystallization kinetics of amorphous Ga–Sb–Te chalcogenide films: Part I. Nonisothermal studies by differential scanning calorimetry

2004 ◽  
Vol 19 (10) ◽  
pp. 2929-2937 ◽  
Author(s):  
Chain-Ming Lee ◽  
Yeong-Iuan Lin ◽  
Tsung-Shune Chin
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Crystallization Kinetics ◽  
Crystallization Temperature ◽  
Ternary Phase Diagram ◽  
Film Deposition ◽  
Rate Dependency ◽  
Scanning Calorimetry ◽  
Kinetics Parameters ◽  
Kinetics Of

Nonisothermal crystallization kinetics of amorphous chalcogenide Ga–Sb–Te films with compositions along the pseudo-binary tie-lines connecting Sb7Te3−GaSb and Sb2Te3–GaSb of the ternary phase diagram were investigated by means of differential scanning calorimetry. Powder samples were prepared firstly by film deposition using a co-sputtering method; the films were then stripped from the substrate. The activation energy (Ea) and rate factor (Ko) were evaluated from the heating rate dependency of the crystallization temperature using the Kissinger method. The kinetic exponent (n) was deduced from the exothermic peak integrals using the Ozawa method. The crystallization temperature (Tx = 181 to 327 °C) and activation energy (Ea= 2.8 to 6.5 eV) increased monotonically with increasing GaSb content and reached a maximum value in compositions located at the vicinity of GaSb. The kinetic exponent is temperature dependent and shows higher values in the SbTe-rich compositions. Promising media compositions worthy of further studies were identified through the determined kinetics parameters.

scholarly journals KINETIC STUDY OF SYNTHESIS REACTION OF LIGNOSULFONATE USING ISOTHERMAL DIFFERENTIAL SCANNING CALORIMETRY METHOD

2017 ◽  
Vol 55 (4) ◽  
pp. 443 ◽  
Author(s):  
Giang Truong Nguyen ◽  
Kien Trung Tran ◽  
Thiem Van Pham ◽  
Hoa Thi Nguyen
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Kinetic Study ◽  
Preexponential Factor ◽  
Synthesis Reaction ◽  
Scanning Calorimetry ◽  
Differential Scanning Calorimetry Method ◽  
Kinetics Of

The kinetics of lignin methylsulfonation were studied in solution by using differential scanning calorimetry (DSC) techniques under an isothermal program, at 55, 65, 75 and 85°C, respectively. It was found that activation energy, Eα =  41.26 kJ/mol, and preexponential factor A was 1.85×103 s-1.

Curing Kinetics of Octaepoxysilsesquioxane/DDS System

2011 ◽  
Vol 233-235 ◽  
pp. 1834-1837
Author(s):  
Zeng Ping Zhang ◽  
Jian Zhong Pei ◽  
Shuan Fa Chen ◽  
Hong Zhao Du ◽  
Yong Wen
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Curing Kinetics ◽  
Scanning Calorimetry ◽  
Exponential Factor ◽  
Inorganic Hybrid ◽  
Oligomeric Silsesquioxane ◽  
Kinetics Of ◽  
Epoxy Groups ◽  
Important Kind

Polyhedral oligomeric silsesquioxane (POSS) can be incorporated into polymers to obtain organic/inorganic hybrid materials. Octaepoxysilsesquioxane (E-POSS) with eight reactive epoxy groups per molecule is an important kind of POSS. E-POSS was cured with 4,4'-diaminodiphenylsulfone diamine (DDS) in this study. The curing kinetics of the E-POSS/DDS system was studied by using differential scanning calorimetry (DSC). Kinssinger and Flynn-Wall-Ozawa methods were used to obtain the activation energy and pre-exponential factor of the curing reaction.

Curing Kinetics of Cyano Functionalized Benzoxazine

2011 ◽  
Vol 233-235 ◽  
pp. 2337-2340
Author(s):  
Wen Jin Chen ◽  
Xiao Bo Liu
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Differential Scanning Calorimetry ◽  
Theoretical Calculations ◽  
Curing Kinetics ◽  
High Thermal Stability ◽  
Order Model ◽  
Scanning Calorimetry ◽  
Autocatalytic Model ◽  
Kinetics Of

A multifunctional benzoxazine monomer (BZCN) was synthesized, which has several outstanding properties, such as high thermal stability and high glass transition. To better understand the curing kinetics of BZCN, isothermal differential scanning calorimetry measurements were used to determine the kinetic parameters and the kinetic models of the curing processes of benzoxazine monomer with cyano functionality. The result shows the mechanism of the curing reaction of BZCN exhibits autocatalytic model, but doesn’t meet nth-order model. Owing to the effects of catalysis of cyano functionality, the activation energy is 89.65KJ•mol-1and the total order of reaction is 1.84, which is quite different from that of normal benzoxazine. The theoretical calculations matched reasonably well with the experimental results.

Curing Kinetics of Silicone Epoxy Resin Containing Fluorene

2014 ◽  
Vol 936 ◽  
pp. 28-33 ◽  
Author(s):  
Wei Xing Deng ◽  
Yuan Wei Zhong ◽  
Jie Qin ◽  
Xue Bing Huang ◽  
Jin Wen Peng
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Ftir Spectroscopy ◽  
Epoxy Resin ◽  
1H Nmr ◽  
Chemical Structure ◽  
Curing Kinetics ◽  
Curing Agent ◽  
Scanning Calorimetry ◽  
Kinetics Of

A new epoxy resin based on dichlorosilane and 9,9-bis (4-hydroxyphenyl) fluorene was synthesized to produce a highly heat-resistant network. The chemical structure was characterized with FTIR spectroscopy and 1H-NMR. 4-4′-Diaminodiphenylsulfone (DDS) was used as the curing agent. The curing kinetics of different epoxy/DDS systems were investigated using non-isothermal differential scanning calorimetry (DSC). The results showed that the values of activation energy (E) were affected by the chemical structure of epoxy resin, and BPEBF exhibited lower curing reactivity towards DDS compared to E-51.

scholarly journals Studies on Sheet Explosive Formulation Based on Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine and Hydroxyl Terminated Polybutadiene

2017 ◽  
Vol 67 (6) ◽  
pp. 617 ◽  
Author(s):  
Suresh Kumar Jangid ◽  
Mrityunjay Kumar Singh ◽  
Vasant Jadavji Solanki ◽  
Rabindra Kumar Sinha ◽  
Krothapalli Prabhakara Subrahmania Murthy
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Kinetic Method ◽  
Decomposition Kinetics ◽  
Thermal And Mechanical Properties ◽  
Binder System ◽  
Scanning Calorimetry ◽  
Velocity Of Detonation ◽  
Kinetics Of

<p class="p1">The effect of replacing hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in HTPB-binder on the performance, sensitivity, thermal, and mechanical properties of the sheet explosive formulation has been studied. The maximum loading of HMX was achieved up to 78 per cent in HTPB-binder system. The velocity of detonation (VOD) of HMX-based sheet explosive was observed about 7300 m/s which is marginally higher than existing RDX-based sheet explosive formulation (RDX/HTPB-binder, 80/20). The VOD trends were verified by theoretical calculation by BKW code using FORTRAN executable program. The thermal decomposition kinetics of sheet explosive formulations was investigated by differential scanning calorimetry. The activation energy for sheet explosive formulation HMX/HTPB-binder (78/22) was calculated using Kissinger kinetic method and found to be 170.08 kJ/mol, infer that sheet explosive formulation is thermally stable.</p>

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