scholarly journals The use of differential calculation methods for the destruction of copolymers of polyethylene glycol fumarate with the acrylic acid

2020 ◽  
Vol 99 (3) ◽  
pp. 4-10
Author(s):  
M.Zh. Burkeev ◽  
◽  
A.Zh. Sarsenbekova ◽  
A.N. Bolatbay ◽  
E.M. Tazhbaev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Polyethylene Glycol ◽  
Acrylic Acid ◽  
Polyester Resin ◽  
Thermodynamic Characteristics ◽  
Nitrogen Atmosphere ◽  
Inert Medium ◽  
Good Convergence ◽  
Sample Decomposition ◽  
First Time

In this work, the thermal decomposition of copolymers based on polyethylene glycol fumarate with the acrylic acid using various ratios of initial monomers has been studied for the first time. The samples were studied in air and nitrogen. According to the thermograms analysis, it was found that the copolymer sample decomposition begins at higher temperatures for a copolymer with high content of polyester resin. The copolymer is vigorously oxidized by the oxygen when heated in air, and one can observe almost complete sample decomposition, whereas it decomposes with a residue of ~ 15% in an inert medium. The activation energies for copolymers with different compositions were estimated using the differential methods of Freeman-Carroll, Achar and Sharpe-Wentworth. The activation energy values found by the three methods demonstrated a good convergence. It was shown that, the activation energy values are higher (~ 200 kJ/mol in the inert medium, and ~ 95 kJ/mol in the oxygen atmosphere) for a copolymer with a lower composition of polyester resin, and the activation energy is ~180 and ~85 kJ/mol for a copolymer with a greater composition of p-EGF-AA. The copolymer is more thermostable in the nitrogen atmosphere according to the kinetic parameters. Additionally, there were determined the thermodynamic characteristics, such as the Gibbs energy (∆G) and the entropy (∆S). They also confirm the destruction process dependence on the components ratio in the synthesized copolymer.

scholarly journals Thermal decomposition kinetics of raw and treated olive waste

2019 ◽  
Vol 23 (6 Part A) ◽  
pp. 3501-3512
Author(s):  
Zhihong Wang ◽  
Chengzhang Wang ◽  
Mijun Peng
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Thermodynamic Characteristics ◽  
Nitrogen Atmosphere ◽  
Enzyme Hydrolysis ◽  
Conversion Degree ◽  
Thermal Decomposition Mechanism ◽  
Scanning Calorimetry ◽  
Two Samples ◽  
Olive Waste

The pyrolysis characteristic of raw and ultrasound assisted enzyme hydrolysis treated (UAEH) olive waste was investigated using the thermogravimetric analysis at 5, 10, 15, and 20?C per minute in the nitrogen atmosphere. The thermal decomposition was divided into three stages in the thermograph curve, and the thermogravimetric curve showed the same decomposition trend for two samples. The temperature interval and peak temperature were different for two different samples, and moved to higher temperature with the increase in heating rate. Differential thermogravimetric and differential scanning calorimetry curves depicted that the structure and composition of samples were changed by UAEH. Meanwhile, the kinetic parameters were calculated by the Kissinger, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, and Coats-Redfern methods. For untreated and treated olive waste, the Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa methods revealed the similar kinetic characteristics for the conversion degree from 0.1 to 0.9, and the average values of activation energy were 201.42 kJ/mol and 162.97 kJ/mol, respectively. The change in activation energy was clearly dependent on the extent of conversion. The Coats-Redfern method suggested the second-order model (F2, f(?) = (1 ? ?)2) could be used to better describe the thermal decomposition mechanism of untreated and treated olive waste. Besides, thermodynamic characteristics of olive waste treated were consistent with that of the untreated sample.

scholarly journals Comparison of α-Tocopherol, α-Tocopherol Acetate, and α-Tocopheryl Polyethylene Glycol Succinate 1000 Absorption by Caco-2 TC7 Intestinal Cells

Nutrients ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 129
Author(s):  
Charlotte Cuerq ◽  
Claire Bordat ◽  
Charlotte Halimi ◽  
Emilie Blond ◽  
Marion Nowicki ◽  
...  
Keyword(s):  
Polyethylene Glycol ◽  
High Performance ◽  
Lipid Extraction ◽  
Free Form ◽  
Glycol Succinate ◽  
Tocopherol Acetate ◽  
Apical Side ◽  
Basolateral Side ◽  
Human Enterocyte ◽  
First Time

(1) Background: vitamin E is often supplemented in the form of tocopherol acetate, but it has poor bioavailability and can fail to correct blood tocopherol concentrations in some patients with severe cholestasis. In this context, α-tocopheryl polyethylene glycol succinate 1000 (TPGS) has been of value, but very little is known about the mechanisms of its absorption. The aim of our work was to evaluate the mechanisms of absorption/secretion of TPGS compared to tocopherol acetate (TAC) and α-tocopherol by human enterocyte-like Caco-2 TC7 cells. (2) Methods: two weeks post-confluence Caco-2 cells were incubated with tocopherol- or TAC- or TPGS-rich mixed micelles up to 24 h and, following lipid extraction, TAC and tocopherol amounts were measured by high performance liquid chromatography (HPLC) in apical, cellular, and basolateral compartments. (3) Results: at equivalent concentrations of tocopherol in the apical side, the amounts of tocopherol secreted at the basolateral pole of Caco-2 cells are (i) significantly greater when the tocopherol is in the free form in the micelles; (ii) intermediate when it is in the TAC form in the micelles (p < 0.001); and (iii) significantly lower with the TPGS form (p < 0.0001). Interestingly, our results show, for the first time, that Caco-2 cells secrete one or more esterified forms of the vitamin contained in TPGS at the basolateral side.

scholarly journals Synthesis and electrical characterization of Ca2Nd4Ti6O20 ceramics

2016 ◽  
Vol 34 (1) ◽  
pp. 164-168
Author(s):  
Raz Muhammad ◽  
Muhammad Uzair ◽  
M. Javid Iqbal ◽  
M. Jawad Khan ◽  
Yaseen Iqbal ◽  
...  
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Room Temperature ◽  
Sol Gel ◽  
Electrical Characterization ◽  
Sintered Sample ◽  
First Time ◽  
Alkoxide Precursors ◽  
Room Temperature Dielectric Constant

AbstractCa2Nd4Ti6O20, a layered perov skite structured material was synthesized via a chemical (citrate sol-gel) route for the first time using nitrates and alkoxide precursors. Phase analysis of a sample sintered at 1625 °C revealed the formation of an orthorhombic (Pbn21) symmetry. The microstructure of the sample after sintering comprised rod-shaped grains of a size of 1.5 to 6.5µm. The room temperature dielectric constant of the sintered sample was 38 at 100 kHz. The remnant polarization (Pr) and the coercive field (Ec) were about 400 μC/cm2 and 8.4 kV/cm, respectively. Impedance spectroscopy revealed that the capacitance (13.7 pF) and activation energy (1.39 eV) of the grain boundary was greater than the capacitance (5.7 pF) and activation energy (1.13 eV) of the grain.

Non-isothermal degradation kinetics for polycarbonate/ polymethylphenylsilsesquioxane composites

e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Jiangbo Wang ◽  
Zhong Xin
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Thermal Degradation ◽  
Flame Retardancy ◽  
Degradation Kinetics ◽  
Degradation Process ◽  
Nitrogen Atmosphere ◽  
Ozawa Method ◽  
Degradation Behaviors ◽  
Thermal Degradation Process

AbstractThe thermal degradation behaviors of PC/PMPSQ (polymethylphenylsilsesquioxane) systems were investigated by thermogravimetric analysis (TGA) under non-isothermal conditions in nitrogen atmosphere. During non-isothermal degradation, Kissinger and Flynn-Wall-Ozawa methods were used to analyze the thermal degradation process. The results showed that a remarkable decrease in activation energy ( E ) was observed in the early and middle stages of thermal degradation in the presence of PMPSQ, which indicated that the addition of PMPSQ promoted the thermal degradation of PC. Flynn-Wall-Ozawa method further revealed that PMPSQ significantly increased the activation energy of PC thermal degradation in the final stage, which illustrated that the PMPSQ stabilized the char residues and improved the flame retardancy of PC in the final period of thermal degradation process

scholarly journals Kinetic Monte Carlo Simulation of Clustering in an Al-Mg-Si-Cu Alloy

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4523
Author(s):  
Qilu Ye ◽  
Jianxin Wu ◽  
Jiqing Zhao ◽  
Gang Yang ◽  
Bin Yang
Keyword(s):  
Activation Energy ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Kinetic Monte Carlo ◽  
Complex Interaction ◽  
Cu Alloy ◽  
Cu Alloys ◽  
Simulation Results ◽  
Small Clusters ◽  
First Time

The mechanism of the clustering in Al-Mg-Si-Cu alloys has been a long-standing controversial issue. Here, for the first time, the mechanism of the clustering in the alloy was investigated by a Kinetic Monte Carlo (KMC) approach. In addition, reversion aging (RA) was carried out to evaluate the simulation results. The results showed that many small-size clusters formed rapidly in the early stages of aging. With the prolongation of aging time, the clusters merged and grew. The small clusters formed at the beginning of aging in Al-Mg-Si-Cu alloy were caused by initial vacancies (quenching vacancies). The merging and decomposition of the clusters were mainly caused by the capturing of vacancies, and the clusters had a probability to decompose before reaching a stable size. After repeated merging and decomposition, the clusters reach stability. During RA, the complex interaction between the cluster merging and decomposition leaded to the partial irregular change of the hardness reduction and activation energy.

scholarly journals Non-Isothermal Sublimation Kinetics of 2,4,6-Trinitrotoluene (TNT) Nanofilms

Molecules ◽  
2019 ◽  
Vol 24 (6) ◽  
pp. 1163 ◽  
Author(s):  
Walid Hikal ◽  
Brandon Weeks
Keyword(s):  
Activation Energy ◽  
Analytical Techniques ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Absorbance Spectroscopy ◽  
Calculated Activation Energy ◽  
Sublimation Kinetics ◽  
Sublimation Rates ◽  
First Time ◽  
Kinetics Of

Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for 2,4,6-trinitrotoluene (TNT) continuous nanofilms in air using rising-temperature UV-Vis absorbance spectroscopy at different heating rates. The TNT films were prepared by the spin coating deposition technique. For the first time, the most widely used procedure to determine sublimation rates using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) was followed in this work using UV-Vis absorbance spectroscopy. The sublimation kinetics were analyzed using three well-established calculating techniques. The non-isothermal based activation energy values using the Ozawa, Flynn–Wall, and Kissinger models were 105.9 ± 1.4 kJ mol−1, 102.1 ± 2.7 kJ mol−1, and 105.8 ± 1.6 kJ mol−1, respectively. The calculated activation energy agreed well with our previously reported isothermally-measured value for TNT nanofilms using UV-Vis absorbance spectroscopy. The results show that the well-established non-isothermal analytical techniques can be successfully applied at a nanoscale to determine sublimation kinetics using absorbance spectroscopy.

PVP Stabilized Ruthenium (0) Nanorods as Effective Catalysts in Hydrogen Generation from the Hydrolysis of Sodium Borohydride

2011 ◽  
Vol 197-198 ◽  
pp. 1577-1581 ◽  
Author(s):  
Shu Ge Peng ◽  
Jun Na Liu ◽  
Xiao Fei Liu ◽  
Yu Qing Zhang ◽  
Jun Zhang
Keyword(s):  
Activation Energy ◽  
Microwave Heating ◽  
Absorption Spectra ◽  
Catalytic Property ◽  
Sodium Borohydride ◽  
Boiling Point ◽  
Hydrogen Generation ◽  
First Time ◽  
Hydrolysis Of

Poly (N-vinyl-2-pyrrolidone) (PVP) - stabilized ruthenium (0) nanorods have been successfully synthesized by refluxing ruthenium (Ⅲ) chloride (RuCl3) in low boiling point alcohols (including ethanol, n-propanol, and n-butanol) using microwave heating for the first time. The effects of low boiling point alcohols on the preparation and catalytic property of ruthenium nanorods were discussed. UV-Vis absorption spectra indicated ruthenium nanorods could be synthesized in n-butanol after 2 h refluxing, far below the refluxing time in ethanol and n-propanol. The activation energy of the hydrolysis of NaBH4 catalyzed by Ruthenium (0) nanorods obtained in ethanol, n-propanol, and n-butanol were determined to be 41.1, 33.3, and 27.9 kJ / mol, respectively.

Polyacryloyl hydrazide based injectable & stimuli responsive hydrogels with tunable properties

2014 ◽  
Vol 2 (42) ◽  
pp. 7429-7439 ◽  
Author(s):  
Anuj Kumar ◽  
Sabindra K. Samal ◽  
Rupesh Dash ◽  
Umaprasana Ojha
Keyword(s):  
Polyethylene Glycol ◽  
Acrylic Acid ◽  
Diethyl Malonate ◽  
Synthesis And Characterization ◽  
Cross Linking ◽  
Stimuli Responsive ◽  
Polyethylene Glycol Diacrylate ◽  
Glycol Diacrylate ◽  
Responsive Hydrogels

The synthesis and characterization of a series of injectable and stimuli responsive hydrogels based on polyacryloyl hydrazide have been accomplished using dimethyl 2,2′-thiodiacetate, acrylic acid, diethyl malonate and polyethylene glycol diacrylate as cross-linkers through a chemical or dual cross-linking pathway.

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