scholarly journals Isothermal Kinetics of Epoxyphosphazene Cure

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 297
Author(s):  
Natalia V. Bornosuz ◽  
Irina Yu. Gorbunova ◽  
Viktoria V. Petrakova ◽  
Vyacheslav V. Shutov ◽  
Vyacheslav V. Kireev ◽  
...  
Keyword(s):  
Order Approximation ◽  
Model Fitting ◽  
Isothermal Kinetics ◽  
Low Molecular Weight ◽  
Scanning Calorimetry ◽  
Diffusion Controlled ◽  
Isoconversional Analysis ◽  
Friedman Method ◽  
Amine Curing ◽  
Kinetics Of

The influence of epoxycyclophosphazene modifier on the process of epoxy-amine curing was studied by differential scanning calorimetry (DSC). The study revealed that the curing process of epoxyphosphazene binders with 4′4′diaminodiphenylsulfone (DDS) provides more complete curing of the formulations in comparison with ones applying low molecular-weight polyamide curing agent (L-20). The isothermal kinetics of curing was described by means of model fitting and the isoconversional approach (Friedman method). Accurate n-order approximation was obtained for all systems under study. In particular, the 2-order equation fits well with the main part of curing excluding high degrees of conversion. The process of curing could be distinguished into three zones. The transition from zone 2 to zone 3 correlates with gelation. According to the isoconversional analysis by Friedman method, the diffusion-controlled mechanism is found at final stage of curing.

scholarly journals Synthesis and Polymerization Kinetics of Rigid Tricyanate Ester

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1686
Author(s):  
Andrey Galukhin ◽  
Roman Nosov ◽  
Ilya Nikolaev ◽  
Elena Melnikova ◽  
Daut Islamov ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Single Step ◽  
Polymerization Kinetics ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Diffusion Controlled ◽  
Polymerization Product ◽  
The One ◽  
Kinetics Of

A new rigid tricyanate ester consisting of seven conjugated aromatic units is synthesized, and its structure is confirmed by X-ray analysis. This ester undergoes thermally stimulated polymerization in a liquid state. Conventional and temperature-modulated differential scanning calorimetry techniques are employed to study the polymerization kinetics. A transition of polymerization from a kinetic- to a diffusion-controlled regime is detected. Kinetic analysis is performed by combining isoconversional and model-based computations. It demonstrates that polymerization in the kinetically controlled regime of the present monomer can be described as a quasi-single-step, auto-catalytic, process. The diffusion contribution is parameterized by the Fournier model. Kinetic analysis is complemented by characterization of thermal properties of the corresponding polymerization product by means of thermogravimetric and thermomechanical analyses. Overall, the obtained experimental results are consistent with our hypothesis about the relation between the rigidity and functionality of the cyanate ester monomer, on the one hand, and its reactivity and glass transition temperature of the corresponding polymer, on the other hand.

scholarly journals Non-Isothermal Crystallization Kinetics of Injection Grade PHBV and PHBV/Carbon Nanotubes Nanocomposites Using Isoconversional Method

2020 ◽  
Vol 4 (2) ◽  
pp. 52
Author(s):  
Thaís Larissa do Amaral Montanheiro ◽  
Beatriz Rossi Canuto de Menezes ◽  
Larissa Stieven Montagna ◽  
Cesar Augusto Gonçalves Beatrice ◽  
Juliano Marini ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Crystallization Kinetics ◽  
Isothermal Crystallization ◽  
Model Fitting ◽  
Polarized Light ◽  
Isoconversional Method ◽  
Degree Of Crystallinity ◽  
Gamma Aminobutyric Acid ◽  
Scanning Calorimetry ◽  
Kinetics Of

Carbon nanotubes (CNT)-reinforced polymeric composites are being studied as promising materials due to their enhanced properties. However, understanding the behavior of polymers during non-isothermal crystallization is important once the degree of crystallinity and crystallization processes are affected when nanoparticles are added to matrices. Usually, crystallization kinetics studies are performed using a model-fitting method, though the isoconversional method allows to obtain the kinetics parameter without assuming a crystallization model. Therefore, in this work, CNTs were oxidized (CNT-Ox) and functionalized with gamma-aminobutyric acid (GABA) (CNT-GB) and incorporated into a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrix. The influence of the addition and functionalization of CNT in the crystallization kinetics of PHBV was evaluated using the isoconversional method with differential scanning calorimetry (DSC), and by polarized light optical microscopy (PLOM) and Shore D hardness. The incorporation and functionalization of CNT into PHBV matrix did not change the Šesták and Berggren crystallization model; however, the lowest activation energy was obtained for the composite produced with CNT-GB, suggesting a better dispersion into the PHBV matrix. PLOM and Shore D hardness confirmed the results obtained in the kinetics study, showing the smallest crystallite size for CNT-containing nanocomposites and the highest hardness value for the composite produced with CNT-GB.

On the Mechanism of Milling Induced Disordering in AlFe

1996 ◽  
Vol 460 ◽  
Author(s):  
M. T. Clavaguera-Mora ◽  
J. Zhu ◽  
M. Meyer ◽  
L. Mendoza-Zelis ◽  
F. H. Sanchez ◽  
...  
Keyword(s):  
Long Range ◽  
Milling Time ◽  
Continuous Heating ◽  
X Ray Diffraction ◽  
Mechanical Grinding ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Diffusion Controlled ◽  
Transmission Mössbauer Spectroscopy ◽  
Kinetics Of

ABSTRACTThe evolution of the B2-AlFe phase during mechanical grinding in Ar has been examined as a function of milling time by X-Ray diffraction, transmission Mössbauer spectroscopy and differential scanning calorimetry. Short and long range disorder was observed to increase with the mechanical treatment up to the attainment of a steady state. The evolution of the long range order parameter and of the local atomic configurations at Fe sites were analyzed in terms of possible mechanisms for milling induced disordering. The kinetics of the thermal reordering was studied under continuous heating and isothermal calorimetrie regimes. Modeling of the reordering processes by diffusion controlled growth of pre-existing ordered grains is presented as well as the estimated values of both the enthalpy and the activation energy of the reordering process. The results are consistent with a non uniform distribution of disorder throughout the sample and will be compared with preceding information on related systems.

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 ISOTHERMAL CURING KINETICS OF POLYMETHACRYLIMIDE/NANO-SiO2 COMPOSITES BASED ON A DYNAMIC THERMOMECHANICAL ANALYSIS

2021 ◽  
Vol 55 (2) ◽  
pp. 293-304
Author(s):  
Jing Zhang ◽  
Yi-min Wu ◽  
Xu Ma ◽  
Bao-Yu Huang ◽  
Song Lv ◽  
...  
Keyword(s):  
Activation Energy ◽  
Integral Method ◽  
Model Fitting ◽  
Curing Kinetics ◽  
Thermomechanical Analysis ◽  
Avrami Model ◽  
Nano Sio2 ◽  
Friedman Method ◽  
Kinetics Of ◽  
Relative Conversion

The isothermal curing kinetics of polymethacrylimide/nano-SiO2 composites were investigated using a dynamic thermomechanical analysis. The relative conversion was defined with the storage modulus. The Avrami model-fitting method, Friedman method and integral method were applied to analyze the curing kinetics. The storage modulus and loss modulus increased appreciably, spanning three orders of magnitude throughout the curing. The frequency correlation of the relative conversion was noticeable at 180 °C because the glass transition took place when the curing degree was not high enough. The Avrami model-fitting analysis gave good fits for the experimental data. The activation energy calculated with the Avrami equation changed from 65.46 kJ/mol to 25.28 kJ/mol at 180–190 °C, while at 190–200 °C, the activation energy changed from 107.14 kJ/mol to 63.82 kJ/mol. The model-free analysis revealed the dependence of the activation energy on the relative conversion. The activation energy increased from 104.3 kJ/mol to 130.6 kJ/mol with the use of the Friedman method when the relative conversion ranged between 0.4–0.8. Similarly, the activation energy calculated with the integral method increased from 71.5 kJ/mol to 103.4 kJ/mol. When the relative conversion exceeded 0.8, the activation energy decreased gradually. The mobility of the reactive groups was hindered and the crosslinking density of the composite was much higher. The curing kinetics became diffusion controlled. The activation energy of the PMI/SiO2 composite was greater than that of PMI, which could be attributed to the hindrance effect caused by nano-SiO2.

SOĞUK HADDELENMİŞ AA3105 VE AA5005 LEVHALARIN DSC ANALİZİ İLE YENİDEN KRİSTALLENME KİNETİĞİ

2021 ◽  
Vol 8 (17) ◽  
pp. 80-85
Author(s):  
Atae RAOUGUI ◽  
Ion GRECU ◽  
Volkan Murat YILMAZ ◽  
Kenan YILDIZ
Keyword(s):  
Differential Scanning Calorimetry ◽  
Aluminum Alloy ◽  
Activation Energies ◽  
Isothermal Kinetics ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Recrystallization Kinetics ◽  
Model Free ◽  
Cold Rolled ◽  
Kinetics Of

In this study, the non-isothermal recrystallization kinetics of cold rolled AA3105 and AA5005 aluminum alloy sheets obtained from ASAŞ Aluminum located in Akyazı-Sakarya was studied by using differential scanning calorimetry (DSC). The non – isothermal kinetics was performed by using Kissenger, Boswell, Ozawa and Starink methods known as model – free methods. The recrystallization temperatures on DSC graphics at different heating rates (β) were deduced and the activation energies were calculated from the slopes from Y – 1/T diagrams. Y is ln(β/T2) for Kissenger, ln(β/T) for Boswell, ln(β) for Ozawa and ln(β/T1.92) for Starink. The results showed that the activation energies of recrystallization are in the range of 194 – 206 kJ/mol for cold rolled AA5005 sheet and in the range of 235 – 257 kJ/mol for cold rolled AA3105 sheet, according to four non-isothermal kinetics model.

Kinetic investigation of a complex curing of the guaiacol bio-based benzoxazine system

e-Polymers ◽  
2016 ◽  
Vol 16 (3) ◽  
pp. 199-206 ◽  
Author(s):  
Aleš Ručigaj ◽  
Špela Gradišar ◽  
Matjaž Krajnc
Keyword(s):  
Curing Kinetics ◽  
Second Stage ◽  
Diffusion Controlled ◽  
Polymerization Behavior ◽  
Overlapped Peaks ◽  
Friedman Method ◽  
Apparent Activation Energies ◽  
Stage 1 ◽  
Kinetics Of ◽  
And Diffusion

AbstractCuring kinetics of guaiacol based benzoxazine synthesized from guaiacol, furfurylamine and formaldehyde forming bio-based polybenzoxazine was investigated. The curing process showed complex polymerization behavior, as the exothermal signal consisted of several overlapped peaks. Differentiation and fitting of overlapped peaks was performed by Pearson VII distribution obtaining two separate exothermal signals further associated to stage 1 and stage 2. The apparent activation energies of both stages were determined to be 113.8 kJ mol-1 and 117.5 kJ mol-1, respectively, according to Kissinger. The first could be explained by benzoxazine ring-opening and electrophilic substitution, whereas the second stage corresponds to the rearrangement and diffusion-controlled step. Kinetics of each stage was studied separately. As a result, the first stage was described by Šesták-Berggren autocatalytic model, whereas the second stage appeared to follow nth order kinetics proved by the Friedman method. Application of both kinetic models demonstrated that the predicted curves fit well with the non-isothermal DSC thermograms and as such sufficiently describes the complex curing behavior of guaiacol based benzoxazine.

scholarly journals Studies of dehydration kinetics of Li2SO4·H2O by the master plots method

2007 ◽  
Vol 5 (1) ◽  
pp. 341-348
Author(s):  
Tang Wanjun ◽  
Chen Donghua
Keyword(s):  
Standard Deviation ◽  
Model Fitting ◽  
Isoconversional Method ◽  
Scanning Calorimetry ◽  
Exponential Factor ◽  
Air Atmosphere ◽  
Master Plots Method ◽  
Fitting Method ◽  
Master Plots ◽  
Kinetics Of

AbstractThe kinetics of Li2SO4·H2O dehydration in static air atmosphere was studied on the basis of nonisothermal measurements by differential scanning calorimetry. Dehydration data were subjected to an integral composite procedure, which includes an isoconversional method, a master plots method and a model-fitting method. Avrami-Erofeev equation was found to describe all the experimental data in the range of conversion degrees from 0.1 to 0.9. The determined activation energy equals 65.45 kJ·mol−1 with standard deviation ±0.47 kJ·mol−1. The estimated value of parameter m in Avrami-Erofeev equation is 2.15 with standard deviation ±0.11. Also, the obtained pre-exponential factor is 7.79×105 s−1 with standard deviation ±0.55×105 s−1. The results show that the present integral composite procedure gives self-consistent kinetic parameters.

Formation kinetics of nanocrystalline Fe–4 wt.% Al solid solution during ball milling

1997 ◽  
Vol 12 (6) ◽  
pp. 1429-1432 ◽  
Author(s):  
H. G. Jiang ◽  
R. J. Perez ◽  
M. L. Lau ◽  
E. J. Lavernia
Keyword(s):  
Solid Solution ◽  
Ball Milling ◽  
Structural Evolution ◽  
Milling Process ◽  
Avrami Equation ◽  
Scanning Calorimetry ◽  
Diffusion Controlled ◽  
Interphase Boundaries ◽  
Kinetics Of Formation ◽  
Kinetics Of

Formation of nanocrystalline Fe–4 wt.% Al solid solution has been achieved through SPEX ball milling of blended elemental Fe and Al powders. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) have been employed to follow the structural evolution during the ball-milling process. Exothermic peaks exhibited in DSC diagrams of the powders milled for 10 to 60 min yielded thermal enthalpies corresponding to the formation of Fe–4 wt.% Al solid solution, from which the kinetics of formation were found to follow the Johnson–Mehl–Avrami equation. Assessment of the kinetic parameter n reveals a diffusion controlled mechanism, in which grain and interphase boundaries may play a crucial role, during the solid solution formation of Fe–4 wt.% Al.

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