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Vinyltri(phenylethynyl)silane ((ph–C≡C)3–Si–C=CH2; VTPES) and phenyltri(phenylethynyl)silane ((ph–C≡C)3–Si–ph; PTPES) were synthesized by Grignard reaction. Their molecular structures were characterized by means of 1H NMR, 13C NMR, 29Si NMR, and FT-IR spectroscopy. Their nonisothermal thermal curing processes were characterized by DSC, and the corresponding
kinetic data, for example activation energy (E), pre-exponential factor (A), and the order of the reaction (n), were obtained by the Kissinger method. The results showed that the melting points of VTPES and PTPES were 84 and 116 °C,
respectively. Their curing reaction rates were consistent with first-order kinetic equations. VTPES monomer had a lower activation
energy and curing temperature as a result of coordination between reactive groups. 相似文献
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火焰原子吸收光谱法工作条件的选择对原子吸收光谱分析很重要,但目前用固定助燃气流量、改变燃气流量的方法来选择燃助比,由于燃气流量改变时将引起火焰剧烈变化、从而导致原子化条件不稳定,引起不同文献中实验结果互相矛盾。经过理论讨论,用改进方法,即:固定燃气流量不变、用改变助燃气流量的方法,通过比较单位进样量吸光度来选择燃助比更合理。改进方法实验结果证明:1、现行方法在改变燃气流量时会引起原子化条件改变;2、现行方法在不同的起始实验条件时对实验结果的影响不同;3、改进方法在任意起始条件下结果相同,表明改进方法满足国家标准中“火焰比较稳定”的条件。结论:用改进方法来选择火焰原子吸收光谱法最佳燃助比更合理。 相似文献
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Youqing Hua Dongmei Zhao Xuhui Quan 《Journal of Thermal Analysis and Calorimetry》1995,45(1-2):177-184
The mechanism and kinetics of curing reaction of tetrafunctional epoxy resin (Ag-80)/novel diamines curing (SED) system were studied by non-isothermal and isothermal DSC. Different equivalent ratios of amine-epoxide give rise to different curing mechanisms. The main condensation reaction can be attributed to the reactions between the primary amine and epoxide and between the hydroxyl and epoxide when temperature is below 200°C, and to the reaction between the second-ary amine and epoxide when temperature is above 200°C. The corresponding apparent activation energies are 58.3 kJ·mol?1 and 99.3 kJ·mol?1 respectively. Apparent activation energies of condensation reactions between primary amine and epoxide and between hydroxyl and epoxide are just the same, which are 47.3 kJ·mol?1. 相似文献
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Non-isothermal Differential Scanning Calorimetry and gel time measurements were employed to study the effects of four different tertiary amine accelerators with different molecular structure and substituents on the curing behavior and reactivity of epoxy/dicyandiamide (DICY) system. Results showed that the acceleration behavior depends on three factors: the bulkiness, the number of nitrogen atoms in molecular structure and the electron density of accelerator. Among these, the former two factors demonstrated stronger effect. The results of model fitting kinetic demonstrated that Šesták–Berggren model can well simulate the reaction rates especially for the samples accelerated by 2,4,6-tris(dimethylaminomethyl)-phenol and (Dimethylaminomethyl)phenol. The activation energy projected by Flynn-Wall-Ozawa and Kissinger–Akahira–Sunose methods exposed different amounts for each accelerator while both models revealed similar trends. Moreover, 1-methylimidazol-accelerated samples showed shortest storage life and gel time mainly due to the presence of two nitrogen atoms in a compact structure of accelerator. 相似文献
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Zhen-li Qi Duan-feng Zhang Fei-xiong Chen Jun-yan Miao Bao-zeng Ren 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(13):2308-2313
The thermal stability and kinetics of isothermal decomposition of carbamazepine were studied under isothermal conditions by thermogravimetry (TGA) and differential scanning calorimetry (DSC) at three heating rates. Particularly, transformation of crystal forms occurs at 153.75°C. The activation energy of this thermal decomposition process was calculated from the analysis of TG curves by Flynn-Wall-Ozawa, Doyle, distributed activation energy model, ?atava-?esták and Kissinger methods. There were two different stages of thermal decomposition process. For the first stage, E and logA [s?1] were determined to be 42.51 kJ mol?1 and 3.45, respectively. In the second stage, E and logA [s?1] were 47.75 kJ mol?1 and 3.80. The mechanism of thermal decomposition was Avrami-Erofeev (the reaction order, n = 1/3), with integral form G(α) = [?ln(1 ? α)]1/3 (α = ~0.1–0.8) in the first stage and Avrami-Erofeev (the reaction order, n = 1) with integral form G(α) = ?ln(1 ? α) (α = ~0.9–0.99) in the second stage. Moreover, ΔH ≠, ΔS ≠, ΔG ≠ values were 37.84 kJ mol?1, ?192.41 J mol?1 K?1, 146.32 kJ mol?1 and 42.68 kJ mol?1, ?186.41 J mol?1 K?1, 156.26 kJ mol?1 for the first and second stage, respectively. 相似文献
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3,4-二硝基吡唑热分解及非等温动力学 总被引:4,自引:0,他引:4
采用TG-DSC综合热分析的方法,对3,4-二硝基吡唑(DNP)的热分解和非等温动力学进行了研究。结果表明DNP的热分解分两阶段进行,并且在升温速率达到15K/min时才能明显区分。分别采用Archar微分法和Coats-Redfen积分法计算了DNP第一阶段热分解反应动力学参数:Ea=91.6kJ.mol-1,lnA=42.7s-1。最可能的DNP热分解机理为随机成核和随后生长机理,符合动力学机理函数Avrami-Erofeev方程,n=3。 相似文献
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The kinetics involved in the thermal decomposition of Kapton® polyimide 100HN under nitrogen atmosphere were studied by applying various fitting techniques to the isothermal and non-isothermal gravimetric data. The correlation of the reaction mechanism fitting, the analytical model fitting and the isoconversional method to these data was examined in relation to the kinetic parameters and the kinetic predictions. The mechanisms for solid-state reactions fit the isothermal data very well but result in highly uncertain values for the kinetic parameters when applied to the non-isothermal data. Isoconversional methods show that the apparent activation energy depends on the extent of conversion but do not provide information for the reaction order and the pre-exponential factor. Three single heating-rate analytical models by Coats-Redfern, MacCallum-Tanner and van Krevelen were analysed using the non-isothermal data. A multi-heating rate model is proposed and its validity is compared to the single-heating rate models on the basis of kinetic predictions. 相似文献
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Hee-Chul Yang Min-Woo Lee Ho-Sang Hwang Jei-Kwon Moon Dong-Yong Chung 《Journal of Thermal Analysis and Calorimetry》2014,118(2):1073-1083
Kinetics of two successive thermal decomposition reaction steps of cationic ion exchange resins and oxidation of the first thermal decomposition residue were investigated using a non-isothermal thermogravimetric analysis. Reaction mechanisms and kinetic parameters for three different reaction steps, which were identified from a FTIR gas analysis, were established from an analysis of TG analysis data using an isoconversional method and a master-plot method. Primary thermal dissociation of SO3H+ from divinylbenzene copolymer was well described by an Avrami–Erofeev type reaction (n = 2, g(α) = [?ln(1 ? α)]1/2]), and its activation energy was determined to be 46.8 ± 2.8 kJ mol?1. Thermal decomposition of remaining polymeric materials at temperatures above 400 °C was described by one-dimensional diffusion (g(α) = α 2), and its activation energy was determined to be 49.1 ± 3.1 kJ mol?1. The oxidation of remaining polymeric materials after thermal dissociation of SO3H+ was described by a phase boundary reaction (contracting volume, g(α) = 1?(1 ? α)1/3). The activation energy and the order of oxygen power dependency were determined to be 101.3 ± 13.4 and 1.05 ± 0.17 kJ mol?1, respectively. 相似文献
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The crystallisation behaviour of in situ polymerised cyclic butylene terephthalates (pCBT) and poly(butylene terephthalate)s
(PBT) were studied by differential scanning calorimetry (DSC) both under isothermal and non-isothermal conditions. The crystallisation
was analysed by adopting the Avrami, Ozawa and Kissinger methods for the isothermal and non-isothermal crystallisations, respectively.
An Avrami exponent n between 2 and 3 was found for the pCBTs whereas the exponent ranged between 3 and 4 for the PBTs. The Ozawa exponent m varied for all materials between 2 and 3. Differences in the crystallisation kinetics were also reflected in the related
activation energy data. 相似文献
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Jiao Enxiang Wu Kun Qu Zhencai Liu Yingchun Lu Maoping Nan Bingfei Chen Weilong Liang Liyan 《Journal of Thermal Analysis and Calorimetry》2021,146(3):1063-1076
Journal of Thermal Analysis and Calorimetry - In this work, phosphomolybdic acid (PMoA) was used as a kind of eco-friendly flame retardant precursor. Then, a green intrinsic flame... 相似文献
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《Thermochimica Acta》1987,122(2):413-418
The approaches to overcoming local ambiguity due to the dependence of the kinetic equation parameters are considered. The application of the mathematical apparatus of the Jacobi matrices enables one to determine the number of both independent kinetic parameters and kinetic functions used to describe a process. No more than five parameters in the Šestak-Berggren equation and only some kinetic functions are found to possess independence. 相似文献
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V. M. Gorbachev 《Journal of Thermal Analysis and Calorimetry》1975,8(3):585-587
If, for a series of similar-type chemical transformations in non-isothermal kinetics, identical or closely similar values of T
cr
are observed in the equation 1/T
cr
=1/T
si
+ + (R/E
i)·ln (E
i
q/RT
si
2
the existence of the compensation relationship lnA
i= =E
i/RT
cr
may regularly be assumed. 相似文献
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B.R. Arora R.K. Banerjee T.S.R.Prasad Rao N.K. Mandal N.C. Ganguli S.P. Sen 《Thermochimica Acta》1973,7(1):25-40
Kinetics of decomposition of the precipitates of the ZnO&2sbndAl2O3 system, prepared by coprecipitation and mechanical mixing of the individual precipitates, have been studied. The decomposition of zinc basic carbonate is a first order rate process with an activation energy of 34.5 kcal/mole (Coats and Redfern equation). The decomposition of aluminium hydroxide is also best described as a first order rate process with one break in the Coats and Redfern plot corresponding to activation energies of 29.4 and 8.3 kcal/mole respectively. The entire course of decomposition of coprecipitated as well as mechanically mixed samples cannot be described by any one of the many rate equations available. Consequently, the Coats and Redfern equation has been employed. The plots indicate one or two breaks and thus two to three values of activation energy are reported. From the results it is to be concluded that decomposition of these precipitates is a heterogeneous process. The first step is definitely the decomposition of zinc basic carbonate followed by decomposition of aluminium hydroxide and/or interaction of the two precipitates resulting in the formation of “precursor” to spinel. The results of our earlier investigation on the same system (especially the formation of precursors) are well supported by the results reported in this investigation. p]A new equation (a modified form of the Elovich equation) has been proposed for such heterogeneous decomposition processes. The proposed equation also appears to be the general form of the equations where diffusion is the rate controlling process. 相似文献