含氟聚合物表面能的测算

通过测定参照液体在聚合物表面的接触角,应用Zisman,Fowkes和筏·義人提出的三种方法,测算了数种国产含氟聚合物的表面能。     

Thermal behavior and kinetic modeling of (NH4)4UO2(CO3)3 decomposition under non-isothermal conditions

The thermal behavior and kinetic analysis of ammonium uranyl carbonate decomposition has been studied in inert gas, O₂, and 90%Ar–10%H₂ atmospheres under non-isothermal conditions. The results showed a dependence on specific surface area with the decomposition temperature of ammonium uranyl tri-carbonate (AUC). Specific surface area increases and reaches a maximum between 300 and 400 °C and decreases at T > 400 °C. The reaction paths of AUC decomposition under the three atmospheres were proposed. The integral methods Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) were used for the kinetic analysis. The activation energy averages are 58.01 and 56.19 kJ/mol by KAS and FWO methods, respectively.

     

The effect of surface modification of layer silicates on the thermoanalytical properties of poly(NIPAAm-co-AAm) based composite hydrogels

Thermal analysis of 2-allyl-4-((4-(4-methylbenzyloxy)phenyl)diazenyl)phenol dye was performed in air flow. The compound thermal behavior was investigated using TG, DTG and DSC techniques, under non-isothermal linear regime. Kinetic parameters of the two decomposition steps were obtained by means of multi-heating rates methods. Isoconversioanl methods (KAS and FWO), Invariant Kinetic Parameters method and Perez-Maqueda et al. criterion (by means of CR and FW equations) were used.     

DSC kinetics of the thermal decomposition of copper(II) oxalate by isoconversional and maximum rate (peak) methods

The copper(II) oxalate was synthesized, characterized using FT-IR and scanning electron microscopy and its non-isothermal decomposition was studied by differential scanning calorimetric at different heating rates. The kinetics of the thermal decomposition was investigated using different isoconversional and maximum rate (peak) methods viz. Kissinger–Akahira–Sunose (KAS), Tang, Starink^1.95, Starink^1.92, Flynn–Wall–Ozawa (FWO) and Bosewell. The activation energy values obtained from isoconversional methods of FWO and Bosewell are 0.9 and 3.0 %, respectively, higher than that obtained from other methods. The variation of activation energy, E _α with conversion function, α, established using these different methods were found to be similar. Compared to the FWO method, the KAS method offers a significant improvement in the accuracy of the E _a values. All but the Bosewell maximum rate (peak) methods yielded consistent values of E _α (~137 kJ mol^?1); however, the complexity of the thermal decomposition reaction can be identified only through isoconversional methods.     

Thermal degradation kinetics study and thermal cracking of waste cooking oil for biofuel production

Thermal cracking of waste cooking oil (WCO) for production of liquid fuel has gained special interest due to the growing demand of renewable fuel, depleting fossil fuel reserves and environmental issues. In the present work, thermal cracking of WCO to produce liquid hydrocarbon fuels without any preprocessing has been studied. Moreover, non-isothermal kinetics of WCO using thermogravimetric analysis (TGA) has been studied under an inert atmosphere at various heating rates. According to TGA result, active thermal decomposition of WCO was found to be between 318 and 500 °C. Furthermore, the temperature at which the maximum mass loss rate attained was shifted to higher values as the heating rates increased from 10 to 50 °C min^?1 and the values were found to be approximately similar to that of R ₅₀. Besides, model-free iso-conversion kinetic methods such as Friedman (FM), Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) were used to determine the activation energies of WCO degradation. The average activation energy for the thermal degradation of WCO was found to be 243.7, 211.23 and 222 kJ mol^?1 for FM, KAS and FWO kinetic methods, respectively. Additionally, the cracking of WCO was studied in a semi-batch reactor under an inert atmosphere and the influences of cracking temperature, time and heating rates on product distribution were investigated. From the reaction, an optimum yield of 72 mass% was obtained at a temperature of 475 °C, time of 180 min and a heating rate of 10 °C min^?1. The physicochemical properties studied were in accordance with ASTM standards.     

SYNTHESIS, CHARACTERIZATION AND THERMAL DEGRADATION KINETICS OF POLY(IMINO ISOPHTHALOYL IMINO (2,4,8,10-TETRAOKSOASPIRO [5,5] UNDEKAN-3,9-DIPROPYLENE))

A new polymer,poly(imino isophthaloyl imino(2,4,8,10-tetraoksoaspiro[5,5]undekan-3,9-dipropylene)) [poly(IPIT)]was synthesized by an interfacial polycondensation reaction.The characterization of poly(IPIT)was conducted by using FT-IR,~(13)C-NMR,TG and DTA techniques.The kinetics of the thermal degradation of poly(IPIT)was investigated by thermogravimetric analysis at different heating rates.TG curves showed that the thermal decomposition of poly(IPIT) occurred in three stages.The apparent activation ener...     

Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants

The mechanism and kinetics of thermal degradation of materials developed from cellulose fiber and synergetic fire retardant or expandable graphite have been investigated using thermogravimetric analysis. The model-free methods such as Kissinger–Akahira–Sunose (KAS), Friedman, and Flynn–Wall–Ozawa (FWO) were applied to measure apparent activation energy (E_α). The increased E_α indicated a greater thermal stability because of the formation of a thermally stable char, and the decreased E_α after the increasing region related to the catalytic reaction of the fire retardants, which revealed that the pyrolysis of fire retardant-containing cellulosic materials through more complex and multi-step kinetics. The Friedman method can be considered as the best method to evaluate the E_α of fire-retarded cellulose thermal insulation compared with the KAS and FWO methods. A master-plots method such as the Criado method was used to determine the possible degradation mechanisms. The degradation of cellulose thermal insulation without a fire retardant is governed by a D3 diffusion process when the conversion value is below 0.6, but the materials containing synergetic fire retardant and expandable graphite fire retardant may have a complicated reaction mechanism that fits several proposed theoretical models in different conversion ranges. Gases released during the thermal degradation were identified by pyrolysis–gas chromatography/mass spectrometry. Fire retardants could catalyze the dehydration of cellulosic thermal insulating materials at a lower temperature and facilitate the generation of furfural and levoglucosenone, thus promoting the formation of char. These results provide useful information to understand the pyrolysis and fire retardancy mechanism of fire-retarded cellulose thermal insulation.

     

Non-isothermal kinetic study on the decomposition of Zn acetate-based Sol-gel precursor

The isoconversional methods (Friedman (FR), Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS)) were applied for evaluating the dependencies of the activation energy (E) on the mass loss (Δm) corresponding to the non-isothermal decomposition of two Zn acetate-based gel precursors for ZnO thin films whose preparation differs by the drying temperature of the liquid sol-precursor (125°C for sample A, and 150°C for sample B). Although both investigated samples exhibit similar decomposition steps, strong differences between E vs. Δm curves as well as among the characteristic parameters of the decomposition steps, directly evaluated from TG, DTG and DTA curves, were put in evidence.     

Thermal decomposition and kinetics studies on the 2,2-dinitropropyl acrylate–styrene copolymer and 2,2-dinitropropyl acrylate–vinyl acetate copolymer

In the present work, kinetics of thermal decomposition of 2,2-dinitropropyl acrylate–styrene copolymer (DNPA/St) and 2,2-dinitropropyl acrylate–vinyl acetate copolymer (DNPA/VAc) was investigated by differential scanning calorimetry (DSC). The influence of the heating rate (5, 10, 15, and 20 °C min^?1) on the DSC behavior of the copolymer was verified. The results showed that, as the heating rate was increased, decomposition temperature of the copolymer was increased. Also, the kinetic parameters such as activation energy and frequency factor of the copolymer were obtained from the DSC data by the isoconversional methods proposed by Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO). Average activation energy obtained by KAS and FWO methods for the thermal decomposition reaction of DNPA/St and DNPA/VAc are 157.38 ± 0.27 and 147.67 ± 0.57 kJ mol^?1, respectively. The rate constants for thermal decomposition calculated from the activation parameters showed the structural dependency. The relative stability of two copolymers under 50 °C was in this order: DNPA/St > DNPA/VAc. The results of thermogravimetry (TG) analysis revealed that the main mass changes for DNPA/St and DNPA/VAc occurred in the temperature ranges of 200–270 °C. The DSC-FTIR analysis of DNPA/St indicates that the band intensity of nitro and other groups increased haphazardly from 230 °C due to thermal decomposition.     

Preparation, thermal decomposition and lifetime of Eu(III)-phenanthroline complex doped xerogel

The main purpose of this work is proposing a new method of using non-isothermal formal kinetics analysis to predict the lifetime of luminescent complex materials. The Eu(III)-phenanthroline complex doped xerogel has been in situ synthesized by a catalyst-free sol-gel method. The photoluminescence spectra and TG curves of the xerogel verify the formation and decomposition of Eu(III)-phenanthroline complex in xerogel. The decomposition of the xerogel formally occurs in three steps. The Friedman and FWO isoconversional methods and multivariate non-linear regression method are used for formal kinetic analysis. The overall decomposition process below 800 °C is fitted by three-step consecutive reaction. The best fitted model for each step is F_n (n order reaction, the corresponding function f(α) is (1 − α)ⁿ). Correlation coefficient is 0.99956. The lifetime values of xerogel at different temperatures are predicted based on non-isothermal kinetic models by the 5% decomposition of europium organic complex.     

TATB/氟聚物PBX力学性能、结合能和爆炸性能的模拟计算

Molecular dynamics （MD） method was used to simulate 1,3,5-triamino-2,4,6-trinitrobenzene （TATB） coated with fluorine containing polymers. The mechanical properties and binding energies of PBXs were obtained. It was found that when the number of chain monomers of fluorine containing polymers was the same, the elasticity of TATB/F2314 was increased more greatly than others and the binding energy of TATB/F2311 was the largest among four PBXs. Detonation heat and velocity of such four PBXs were calculated according to theoretical and empirical formulas. The results show that the order of detonation heat is TATB〉TATB/PVDF〉TATB/F2311〉TATB/ F2314 〉 TATB/PCTFE while the order of detonation velocity is TATB/PVDF 〈 TATB/F2311 〈 TATB/F2314 〈 TATB/PCTFE 〈TATB.     

Thermal and kinetic analysis of uranium salts

The thermal decomposition kinetics of UO₂C₂O₄·3H₂O were studied by TG method in a flowing nitrogen, air, and oxygen atmospheres. It is found that UO₂C₂O₄·3H₂O decomposes to uranium oxides in four stages in all atmosphere. The first two stages are the same in the whole atmosphere that correspond to dehydration reactions. The last two stages correspond to decomposition reactions. Final decomposition products are determined with X-Ray powder diffraction method. Decomposition mechanisms are different in nitrogen atmosphere from air and oxygen atmosphere. The activation energies of all reactions were calculated by model-free (KAS and FWO) methods. For investigation of reaction models, 13 kinetic model equations were tested and correct models, giving the highest linear regression, lowest standard deviation, and agreement of activation energy value to those obtained from KAS and FWO equations were found. The optimized value of activation energy and Arrhenius factor were calculated with the best model equation. Using these values, thermodynamic functions (??H ^*, ??S ^*, and ??G ^*) were calculated.     

Effect of CaCO3 Filler Component on Solid State Decomposition Kinetic of PP/LDPE/CaCO3 Composites

In this study, the effect of addition Calcium carbonate (CaCO₃) filler component on solid state thermal decomposition procedures of Polypropylene-Low Density Polyethylene (PP-LDPE; 90/10 wt%) blends involving different amounts (5, 10, 20 wt%) Calcium carbonate (CaCO₃) was investigated using thermogravimetry in dynamic nitrogen atmosphere at different heating rates. An integral composite procedure involving the integral iso-conversional methods such as the Tang (TM), the Kissinger-Akahira-Sunose method (KAS), the Flynn-Wall-Ozawa (FWO), an integral method such as Coats-Redfern (CR) and master plots method were employed to determine the kinetic model and kinetic parameters of the decomposition processes under non-isothermal conditions. The Iso-conversional methods indicated that the thermal decomposition reaction should conform to single reaction model. The results of the integral composite procedures of TG data at various heating rates suggested that thermal processes of PP-LDPE-CaCO₃ composites involving different amounts of CaCO₃ filler component (5, 10, 20 wt%) followed a single step with approximate activation energies of 226.7, 248.9, and 252.0 kJ.mol^{? 1} according to the FWO method, respectively and those of 231.3, 240.1 and 243.0 kJ mol^{? 1} at 5°C min^{? 1} according to the Coats-Redfern method, the reaction mechanisms of all the composites was described from the master plots methods and are P_n model for composite C-1, R_n model for composites C-2 and C-3, respectively. It was found that the thermal stability, activation energy and thermal decomposition process changed by the increasing CaCO₃ filler weight in composite structure.     

Thermal behavior and decomposition kinetics of composite solid propellants in the presence of amide burning rate suppressants

The employment of burning rate suppressants in the solid rocket propellant formulation is long known. Different research activities have been conducted to well understand the mechanism of suppression, but literature about the action of oxamide (OXA) and azodicarbonamide (ADA) on the thermal decomposition of composite propellant is still scarce. The focus of this study is on investigating the effect of burning rate suppressants on the thermal behavior and decomposition kinetics of composite solid propellants. Thermogravimetric analysis (TG) and differential thermal analysis have been used to identify the changes in the thermal and kinetic behaviors of coolant-based propellants. Two main decomposition stages were observed. It was found that OXA played an inhibition effect on both stages, whereas the ADA acts as a catalyst in the first stage and as coolant in the second one. The activation energy dependent on the conversion rate was estimated by two model-free integral methods: Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) based on the TG data obtained at different heating rates. The mechanism of action of coolants on the decomposition of solid propellants was confirmed by the kinetic investigation as well.     

Molecular dynamics simulation of mechanical properties of TATB/fluorine-polymer PBXs along different surfaces

TATB (1,3,5-triamino-2,4,6-trinitrobenzene) is the well-known high insensitive explosive. With TATB as the main body (90% and above) the polymer bonded explosives ( PBXs) contain a small amount of poly-mers (5%―10%). The composite materials with good saf…     

Thermal Kinetics and Decomposition Mechanism of Methylphenylphosphinic Acid and Diphenylphosphinic Acid

Thermal degradation and degradation kinetics of methylphenylphosphinic acid（MPPA） and diphenyl- phosphinic acid（DPPA） were investigated via thermogravimetric analysis（TGA） technique under non-isothermal conditions. The activation energies of the decomposition process for the two compounds were calculated through the Friedman and Kissinger-Akahira-Sunose（KAS） methods. The thermal decomposition mechanism was investigated by the Criado method based on a set of TGA data obtained at different heating rates. It was shown that the activation energies calculated from the decomposition reaction by different methods were consistent with each other. The results show that the probable model for the degradation of MPPA and DPPA agreed with the two-dimensional（D2） and three-dimensional（D4） diffusion models, respectively. Moreover, the thermodynamic functions（△H, △S, △G） of the two decomnosition reactions were also calculated.     

Thermal and kinetic analyses of 2,5-bis(2-hydroxyphenyl)thiazolo[5,4-d]thiazole

Thermal behavior and UV–Vis absorption properties of 2,5-bis(2-hydroxyphenyl)thiazolo[5,4-d]thiazole were investigated in the present study. It was found that decomposition occurs in two stages which correspond to removal of both phenolic rings and degradation of remaining core structure, respectively. After the characterization of decomposition stages, apparent activation energy values of each stage were calculated using model-free isoconversional methods (FWO and KAS). Apparent activation energies of decomposition stages are determined by both methods. Their averages are calculated as 98.232 and 123.253 kJ mol^?1 in consecutive order. UV–Vis absorption properties of this compound have been determined with using different solvents.     

TG,EGA and kinetic study by non-isothermal decomposition of a polyaniline with different dispersion degree

Polyaniline was obtained by oxidizing aniline in hydrochloric acid media with ammonium peroxidisulfate as oxidizing agent. Molar ratio aniline/oxidant was 1 and aniline/acid ratio: ½, at ?5 and 400 °C, respectively, 800 mL water. The both compounds were studied using two different experimental strategies: the coupled TG-EGA (FTIR) technique by decomposition in dynamic air atmosphere and the kinetic analysis of TG data obtained at four heating rates (5, 7, 10 and 15 K min^?1). The kinetic analysis of the TG non-isothermal data was performed with the Flynn–Wall–Ozawa, Friedman’s, and modified non-parametric kinetic (NPK) methods. By means of the coupled techniques spectroscopic arguments on the reaction mechanism were obtained, i.e. the oxidative degradation of the quinoine ring as the first step. The values of the activation energy by the three used methods are in good agreements. According to the NPK method, the termodegradation process consist in physical (diffusion) and chemical steps.     

Novel fluorosilicone thermoplastic vulcanizates prepared via core‐shell dynamic vulcanization: Effect of fluororubber/silicone rubber ratio on morphology,crystallization behavior,and mechanical properties

Recently, we have reported a novel core‐shell dynamic vulcanization method to prepare poly(vinylidene fluoride) (PVDF)/fluororubber (FKM)/silicone rubber (SR) thermoplastic vulcanizates (TPVs) with cross‐linked rubber core‐shell particles. However, the shell thickness on the properties has not been studied in detail. Herein, these PVDF‐based TPVs different FKM‐shell thickness were prepared by changing FKM/SR ratios. The effect of FKM‐shell/SR‐core ratio on morphology, crystallization, and mechanical properties of the ternary TPVs was studied. The results showed that the FKM shell had more positive effect on interfacial‐induced crystallization behavior than the SR core due to its better compatibility with PVDF. When the FKM/SR ratio was <1, FKM was not enough to encapsulate SR completely, which resulted in the formation of imperfect core‐shell structure. However, when the FKM/SR ratio was >1, perfect core‐shell structure was formed. Therefore, the mechanical properties improved with increasing FKM content; especially, a remarkable improvement was observed when FKM/SR ratio was >1. This study could provide more information for the design of TPVs with core‐shell structure.