scholarly journals Melting Kinetics of Nascent Poly(tetrafluoroethylene) Powder

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 791
Author(s):  
Fotis Christakopoulos ◽  
Enrico Troisi ◽  
Theo A. Tervoort
Keyword(s):  
Kinetic Model ◽  
Heating Rate ◽  
Melting Temperature ◽  
Melting Behavior ◽  
Slow Heating ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Exponential Factor ◽  
Melting Kinetics ◽  
Kinetics Of

The melting behavior of nascent poly(tetrafluoroethylene) (PTFE) was investigated by way of differential scanning calorimetry (DSC). It is well known that the melting temperature of nascent PTFE is about 344 ∘ C, but reduces to 327 ∘ C for once molten material. In this study, the melting temperature of nascent PTFE crystals was found to strongly depend on heating rate, decreasing considerably for slow heating rates. In addition, during isothermal experiments in the temperature range of 327 ∘ C < T < 344 ∘ C, delayed melting of PTFE was observed, with complete melting only occurring after up to several hours. The melting kinetics of nascent PTFE were analyzed by means of the isoconversional methodology, and an apparent activation energy of melting, dependent on the conversion, was determined. The compensation effect was utilized in order to derive the pre-exponential factor of the kinetic model. The numerical reconstruction of the kinetic model was compared with literature models and an Avrami-Erofeev model was identified as best fit of the experimental data. The predictions of the kinetic model were in good agreement with the observed time-dependent melting of nascent PTFE during isothermal and constant heating-rate experiments.

scholarly journals Thermal Analysis On The Kinetics Of Magnesium-Aluminum Layered Double Hydroxides In Different Heating Rates

2015 ◽  
Vol 60 (2) ◽  
pp. 1357-1359 ◽  
Author(s):  
Y. Hongbo ◽  
C. Meiling ◽  
W. Xu ◽  
G. Hong
Keyword(s):  
Activation Energy ◽  
Thermal Analysis ◽  
Layered Double Hydroxides ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Exponential Factor ◽  
Thermal Kinetic Parameters ◽  
Double Hydroxides ◽  
Kinetics Of ◽  
Dsc Curves

Abstract The thermal decomposition of magnesium-aluminum layered double hydroxides (LDHs) was investigated by thermogravimetry analysis and differential scanning calorimetry (DSC) methods in argon environment. The influence of heating rates (including 2.5, 5, 10, 15 and 20K/min) on the thermal behavior of LDHs was revealed. By the methods of Kissinger and Flynn-Wall-Ozawa, the thermal kinetic parameters of activation energy and pre-exponential factor for the exothermic processes under non-isothermal conditions were calculated using the analysis of corresponding DSC curves.

Pyrolysis of Sugarcane Bagasse: A Consecutive Reactions Kinetic Model from TGA Experiments

2010 ◽  
Vol 660-661 ◽  
pp. 593-598 ◽  
Author(s):  
Kássia Graciele dos Santos ◽  
Taisa S. Lira ◽  
Valéria V. Murata ◽  
Marco Gianesella ◽  
Marcos A.S. Barrozo
Keyword(s):  
Kinetic Model ◽  
Sugarcane Bagasse ◽  
Room Temperature ◽  
Linear Method ◽  
Pyrolysis Kinetics ◽  
Heating Rates ◽  
Exponential Factor ◽  
Consecutive Reactions ◽  
Kinetics Of ◽  
Good Agreement

The pyrolysis kinetics of sugarcane bagasse in nitrogen flow was studied by thermogravimetric analysis from room temperature to 1173 K at different heating rates (1.5, 3, 5, 10, 15, 20, 30 and 50 K/min). As there are three distinct devolatilization peaks in the DTG curve, each peak was associated to thermal decomposition of an individual biomass subcomponent (hemicellulose, cellulose and lignin). The kinetic model adopted was a consecutive reactions model. The kinetic parameters of the pyrolysis process, such as activation energy and pre-exponential factor, were calculated by least squares non-linear method and Scilab are used as the simulation tool. The simulated results showed a good agreement with the experimental data and the parameters found are similar to reported by the literature.

scholarly journals Effect of Organic Modifier and Clay Content on Non-Isothermal Cold Crystallization and Melting Behavior of Polylactide/Organovermiculite Nanocomposites

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 364
Author(s):  
M. Jesús Fernández ◽  
M. Dolores Fernández
Keyword(s):  
Rate Coefficient ◽  
Crystallization Rate ◽  
Clay Content ◽  
Melting Behavior ◽  
Cold Crystallization ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Crystallization And Melting Behavior ◽  
Kinetics Of ◽  
Nucleating Effect

In clay/polymer nanocomposites, the crystallization behavior and kinetics of the polymer can be affected by the presence of clay, its content and the degree of miscibility between the clay and the polymer matrix. The effect of two different organomodified vermiculites on the non-isothermal cold crystallization and melting behavior of polylactide (PLA) was studied by differential scanning calorimetry (DSC). In the presence of vermiculites, the cold crystallization of PLA occurred earlier, particularly for the highest content of the most miscible organovermiculite with PLA. The cold crystallinity of PLA decreased at low heating rates, notably at high organoclay loadings, and increased at high heating rates, especially at low vermiculite contents. According to the crystallization half-time, crystallization rate coefficient (CRC), and crystallization rate parameter (CRP) approaches, the cold crystallization rate of PLA increased by incorporating vermiculites, with the effect being most noteworthy for the vermiculite showing better compatibility. The Mo model was successful in describing the non-isothermal cold crystallization kinetics of the PLA/vermiculite composites. The melting behavior was affected by the heating rate and the type and content of clay. The nucleating effect of the most compatible clay resulted in the less perfect crystallites. The activation energy was evaluated using the Kissinger and Takhor methods.

Effect of Heating Rate on Chemical Kinetics of Chicken Manure With Different Gas Agents

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Osama M. Selim ◽  
Mohamed S. Hussein ◽  
Ryoichi S. Amano
Keyword(s):  
Carbon Dioxide ◽  
Heating Rate ◽  
Measurement Errors ◽  
Chemical Kinetic ◽  
Chicken Manure ◽  
Slow Heating ◽  
Quasi Equilibrium ◽  
Heating Rates ◽  
Gasification Process ◽  
Kinetics Of

Abstract This paper presents the study on the effect of different heating rates on the pyrolysis and gasification process of the chicken manure. The obtained results are shown by the extent of reaction, the kinetics of the reaction, and differential thermal analysis. In total, 24 cases were carried out; eight heating rates with three different gas agents each. The results show that when using nitrogen or carbon dioxide as gas agents, the reactions were endothermic. Consequently, the energy must be supplied in terms of heating to sustain the reaction. Furthermore, the air gasification was exothermic, which means that the reaction can be sustained without external heating, where the self-ignition was observed between 450 °C–600 °C. The thermal degradation of the three main components of the chicken manure was obtained. The pyrolysis process was divided into two regions at 360 °C and the order of reaction of five for both regions. For the gasification process, it was observed that carbon dioxide had the most complicated mechanism with four stages. Finally, it is recommended to use the lowest heating rate to allow a quasi-equilibrium state through slow heating. Consequently, the delay in response or any transient error can be avoided as they are the main reason for measurement errors. These chemical kinetic parameters can be used in the future for the chicken manure simulation using the order of reaction mechanism for solid-state gasification.

Global Kinetics of the Thermal Decomposition of Materials

1997 ◽  
Author(s):  
Azzedine Missoum ◽  
Ashwani K. Gupta ◽  
Jianrong Chen
Keyword(s):  
Heat Transfer ◽  
Activation Energy ◽  
Heating Rate ◽  
Decomposition Reaction ◽  
Decomposition Process ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Transfer Product ◽  
Product Evolution ◽  
Kinetics Of

Abstract Results on the thermal destruction behavior during the decomposition of cellulose under controlled conditions are presented. Thermogravimetric (TGA) and Differential Scanning Calorimetry (DSC) tests have been carried out on the celluose samples under conditions of various heating rate and surrounding gas environment. Pyrolysis times were also measured for different size particles having different moisture contents in a controlled mixing history reactor (CMHR). The global decomposition kinetics were investigated and it was found that the decomposition process is shifts to higher temperatures at higher heating rates as a result of the competing effects of heat and mass transfer, product diffusion and the reactions kinetics. The Arrhenius parameters for pyrolysis were determined using a first order decomposition reaction of the type, dm = −km dt. It was found that the activation energy, heat of pyrolysis and char yield are a strong function of the heating rate. An increase in heating rate from 5 to 60°C/min resulted in a change of activation energy from 204.19 to 138.31 kJ/mole °C. This heating rate dependence of the kinetics is discussed. The overall decomposition process of the examined materials is generally endothermic. In general, heat transfer, mass diffusion, product evolution, heating rate, temperature and environment are the parameters that control the decomposition process. It was also shown that heat transfer and mass transport have the most effects on the decomposition process.

Effects of additives on the cure kinetics of vinyl ester pultrusion resins

2021 ◽  
pp. 002199832110015
Author(s):  
Alexander Vedernikov ◽  
Yaroslav Nasonov ◽  
Roman Korotkov ◽  
Sergey Gusev ◽  
Iskander Akhatov ◽  
...  
Keyword(s):  
Vinyl Ester ◽  
Mean Squared Error ◽  
Cure Kinetics ◽  
Zinc Stearate ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Different Temperatures ◽  
Predicted Values ◽  
Kinetics Of ◽  
Final Degree

Pultrusion is a highly efficient composite manufacturing process. To accurately describe pultrusion, an appropriate model of resin cure kinetics is required. In this study, we investigated cure kinetics modeling of a vinyl ester pultrusion resin (Atlac 430) in the presence of aluminum hydroxide (Al(OH)3) and zinc stearate (Zn(C18H35O2)2) as processing additives. Herein, four different resin compositions were studied: neat resin composition, composition with Al(OH)3, composition comprising Zn(C18H35O2)2, and composition containing both Al(OH)3 and Zn(C18H35O2)2. To analyze each composition, we performed differential scanning calorimetry at the heating rates of 5, 7.5, and 10 K/min. To characterize the cure kinetics of Atlac 430, 16 kinetic models were tested, and their performances were compared. The model based on the [Formula: see text]th-order autocatalytic reaction demonstrated the best results, with a 4.5% mean squared error (MSE) between the experimental and predicted data. This study proposes a method to reduce the MSE resulting from the simultaneous melting of Zn(C18H35O2)2. We were able to reduce the MSE by approximately 34%. Numerical simulations conducted at different temperatures and pulling speeds demonstrated a significant influence of resin composition on the pultrusion of a flat laminate profile. Simulation results obtained for the 600 mm long die block at different die temperatures (115, 120, 125, and 130 °C) showed that for a resin with a final degree of cure exceeding 95% at the die exit, the maximum difference between the predicted values of pulling speed for a specified set of compositions may exceed 1.7 times.

Investigating the relationship between tack and degree of conversion in DGEBA-based epoxy resin cured with dicyandiamide and diuron

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ali Kuliaei ◽  
Iraj Amiri Amraei ◽  
Seyed Rasoul Mousavi
Keyword(s):  
Epoxy Resin ◽  
Reaction Order ◽  
Theoretical Data ◽  
Cure Kinetics ◽  
Diglycidyl Ether ◽  
Degree Of Conversion ◽  
Ozawa Method ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Kinetics Of

Abstract The purpose behind this research was to determine the optimum formulation and investigate the cure kinetics of a diglycidyl ether of bisphenol-A (DGEBA)-based epoxy resin cured by dicyandiamide and diuron for use in prepregs. First, all formulations were examined by the tensile test, and then, the specimens with higher mechanical properties were further investigated by viscometry and tack tests. The cure kinetics of the best formulation (based on tack test) in nonisothermal mode was investigated using differential scanning calorimetry at different heating rates. Kissinger and Ozawa method was used for determining the kinetic parameters of the curing process. The activation energy obtained by this method was 71.43 kJ/mol. The heating rate had no significant effect on the reaction order and the total reaction order was approximately constant ( m + n ≅ 2.1 $m+n\cong 2.1$ ). By comparing the experimental data and the theoretical data obtained by Kissinger and Ozawa method, a good agreement was seen between them. By increasing the degree of conversion, the viscosity decreased; as the degree of conversion increased, so did the slope of viscosity. The results of the tack test also indicated that the highest tack could be obtained with 25% progress of curing.

scholarly journals Synthesis and characterization of a new conjugated polymer containing bithiazole group and its thermal decomposition kinetics

2020 ◽  
Vol 39 (2) ◽  
pp. 227
Author(s):  
Adnan Kurt ◽  
Hacer Andan ◽  
Murat Koca
Keyword(s):  
Thermal Decomposition ◽  
Heating Rate ◽  
Conjugated Polymer ◽  
Three Dimensional ◽  
Heating Rates ◽  
Diffusion Type ◽  
Optimum Heating ◽  
Rate Loss ◽  
Kinetics Of

A new conjugated polymer containing a bithiazole group is prepared by the polycondensation of 2,2'-diamino-4,4'-bithiazole and terephthaldialdehyde in the presence of glacial acetic acid. The kinetics of thermal degradation of the new polymer are investigated by thermogravimetric analysis at different heating rates. The temperature corresponding to the maximum rate loss shifts to higher temperatures with increasing heating rate. The thermal decomposition activation energies of the conjugated polymer in a conversion range of 3–15 % are 288.4 and 281.1 kJ/mol by the Flynn–Wall–Ozawa and Kissinger methods, respectively. The Horowitz–Metzger method shows that the thermodegradation mechanism of the conjugated polymer proceeds over a three-dimensional diffusion type deceleration D3 mechanism. The optimum heating rate is 20 ºC/min.

scholarly journals Measurement and Evaluation of Calorimetric Descriptors for the Suitability for Evolutionary High-Throughput Material Development

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 149 ◽  
Author(s):  
Anastasiya Toenjes ◽  
Heike Sonnenberg ◽  
Christina Plump ◽  
Rolf Drechsler ◽  
Axel von Hehl
Keyword(s):  
Heating Rate ◽  
High Throughput ◽  
Macro Level ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Characterization Methods ◽  
Material Development ◽  
First Results ◽  
Novel Method ◽  
Measurement And Evaluation

A novel method for evolutionary material development by using high-throughput processing is established. For the purpose of this high-throughput approach, spherical micro samples are used, which have to be characterized, up-scaled to macro level and valued. For the evaluation of the microstructural state of the micro samples and the associated micro-properties, fast characterization methods based on physical testing methods such as calorimetry and universal microhardness measurements are developed. Those measurements result in so-called descriptors. The increase in throughput during calorimetric characterization using differential scanning calorimetry is achieved by accelerating the heating rate. Consequently, descriptors are basically measured in a non-equilibrium state. The maximum heating rate is limited by the possibility to infer the microstructural state from the calorimetric results. The substantial quality of the measured descriptors for micro samples has to be quantified and analyzed depending on the heating rate. In this work, the first results of the measurements of calorimetric descriptors with increased heating rates for 100Cr6 will be presented and discussed. The results of low and high heating rates will be compared and analyzed using additional microhardness measurements. Furthermore, the validation of the method regarding the suitability for the evolutionary material development includes up-scaling to macro level and therefore different sample masses will be investigated using micro and macro samples during calorimetry.

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