融合C80数据的绝热加速量热法热惯量因子修正

受限于仪器原理,绝热加速量热法数据分析需进行热惯量因子修正。然而,现有的修正方法均违背由反应物比热及炉体温度动态追踪效果变化等引起热惯量因子动态变化的事实,导致动力学参数求取存在偏差。针对上述不足,提出一种基于C80与绝热加速量热数据联用的绝热加速量热热惯量因子修正及动力学计算方法。具体步骤如下：基于Friedman法分析C80数据获取无模型动力学参数,将其代入绝热数据求解反应体系比热容与等效热惯量因子乘积,并在绝热平衡方程中由上述乘积替代恒定热惯量因子及比热实现动力学计算。以过氧化二叔丁基(DTBP)和过氧化氢异丙苯(CHP)为实验对象进行实验验证。结果表明,基于两种量热模式联用的热惯量因子修正方法避免了热惯量动态变化对动力学分析的影响,从而获得更加准确的动力学参数。     

融合C80数据的绝热加速量热法热惯量因子修正

受限于仪器原理,绝热加速量热法数据分析需进行热惯量因子修正。然而,现有的修正方法均违背由反应物比热及炉体温度动态追踪效果变化等引起热惯量因子动态变化的事实,导致动力学参数求取存在偏差。针对上述不足,提出一种基于C80与绝热加速量热数据联用的绝热加速量热热惯量因子修正及动力学计算方法。具体步骤如下:基于Friedman法分析C80数据获取无模型动力学参数,将其代入绝热数据求解反应体系比热容与等效热惯量因子乘积,并在绝热平衡方程中由上述乘积替代恒定热惯量因子及比热实现动力学计算。以过氧化二叔丁基(DTBP)和过氧化氢异丙苯(CHP)为实验对象进行实验验证。结果表明,基于两种量热模式联用的热惯量因子修正方法避免了热惯量动态变化对动力学分析的影响,从而获得更加准确的动力学参数。     

CY184/D230体系的分段拟合固化反应动力学

采用非等温示差扫描量热法对低粘度CY184/D230环氧体系的固化反应动力学进行了研究。采用高级等转化率法(Vyazovkin法)求出活化能,通过Málek法进行了模型拟合动力学分析并采用分段拟合法建立了固化反应动力学模型。结果表明,固化反应动力学符合Sesták-Berggren模型,模型拟合曲线与实验数据十分吻合,证实了分段拟合模型的准确性。     

N-甲基氧化吗啉热分解动力学分析

对在纤维素溶剂中具有广泛应用的N-甲基氧化吗啉(NMMO)热分解动力学进行研究。首先利用绝热加速量热仪(ARC)开展绝热分解实验，得到NMMO在绝热条件下的初始分解温度为119.87℃,通过动力学计算得到反应活化能为219.7 kJ·mol^-1,为自分解一级反应。其次通过差示扫描量热仪(DSC)对NMMO进行非等温分解实验，并利用Friedman法、Flynn-Wall-Ozawa法和ASTM E698法3种动力学模型进行分解动力学计算。研究结果显示NMMO的初始分解温度为161.07～186.40℃,反应活化能分别为81～134、75.81～100.34和101.92 kJ·mol^-1。最后利用风险矩阵法定量评估NMMO热分解危险等级为Ⅲ级。该研究结果为降低NMMO生产、储存和运输中发生分解反应的风险提供了理论依据。     

40%DCP溶液的热分解模型

准确的热分解动力学模型有助于人们采取各种安全措施预防和控制物料热失控导致的燃烧爆炸事故。以40%过氧化二异丙苯（DCP）的2,2,4-三甲基戊二醇二异丁酯（DIB）溶液为研究对象,运用差示扫描量热仪（DSC）和绝热量热设备（VSP2）进行了量热实验,并采用TSS软件（Thermal Safety Software）对数据进行动力学分析,建立了两种分解模型：“N级+N级”模型（模型1）和“N级+自催化”模型（模型2）,采用Friedman法和非线性拟合方法求算其动力学参数。在运用所建立的两种模型拟合曲线时,发现两种模型对同种量热模式数据拟合的相关系数非常接近,说明单一量热模式在求算动力学上存在局限性。联合采用基于动态扫描模式的DSC数据及基于绝热模式的VSP2数据共同求算动力学,发现相对于模型2,模型1可以更好地反映分解过程,其两步反应的活化能分别为115.5 kJ·mol^-1和135.7 kJ·mol^-1,指前因子的对数分别为28.3和31.6,反应级数分别为0.40和0.84。研究结果表明采用基于不同量热模式的数据求算动力学有助于确定正确的动力学模型,从而获得准确的动力学参数,并克服单一量热模式下动力学求算的局限性。     

40%DCP溶液的热分解模型

准确的热分解动力学模型有助于人们采取各种安全措施预防和控制物料热失控导致的燃烧爆炸事故。以40%过氧化二异丙苯(DCP)的2,2,4-三甲基戊二醇二异丁酯(DIB)溶液为研究对象,运用差示扫描量热仪(DSC)和绝热量热设备(VSP2)进行了量热实验,并采用TSS软件(Thermal Safety Software)对数据进行动力学分析,建立了两种分解模型:"N级+N级"模型(模型1)和"N级+自催化"模型(模型2),采用Friedman法和非线性拟合方法求算其动力学参数。在运用所建立的两种模型拟合曲线时,发现两种模型对同种量热模式数据拟合的相关系数非常接近,说明单一量热模式在求算动力学上存在局限性。联合采用基于动态扫描模式的DSC数据及基于绝热模式的VSP2数据共同求算动力学,发现相对于模型2,模型1可以更好地反映分解过程,其两步反应的活化能分别为115.5 kJ·mol~(-1)和135.7 kJ·mol~(-1),指前因子的对数分别为28.3和31.6,反应级数分别为0.40和0.84。研究结果表明采用基于不同量热模式的数据求算动力学有助于确定正确的动力学模型,从而获得准确的动力学参数,并克服单一量热模式下动力学求算的局限性。     

DSC研究不饱和聚酯/复合引发体系固化反应动力学

本文介绍了不饱和聚酯树脂（UP）常用的几种固化反应动力学模型,实验采用差示扫描量热法（DSC）研究不饱和聚酯/复合引发体系的等温固化反应动力学。选择修正的自催化模型对等温固化DSC数据进行处理,用最小二乘法进行非线性回归,确定等温反应速率常数k0和反应级数m、n,得到动力学方程。研究结果表明不同温度下该模型拟合曲线的相关系数均在98%以上,与实验数据点相吻合,因此所选模型对该体系是适用的,为不饱和聚酯基复合材料的固化研究提供了理论依据。     

环氧树脂/对甲基苯基双胍固化反应动力学研究

根据非等温和等温DSC数据,采用等转化率法和模型拟合法对环氧树脂/对甲基苯基双胍体系的固化反应过程进行了研究,分析了固化体系在非等温和等温条件下的固化规律。并通过Malek最大概然函数机理法确定了固化反应机理函数,计算出固化反应动力学模型参数。结果表明,考虑了扩散影响的等温自催化反应速率模型对该体系等温固化过程的预测数据与DSC实验数据吻合得更好。同时,在比较非等温和等温自催化动力学模型的计算值与实验值的基础上,结合活化能随固化度的变化规律,对不同温度条件、不同转化率下固化体系的反应历程和机理进行分析,为工业应用中固化工艺条件的优化提供了理论依据。     

PPCMA三元共聚物的非等温交联动力学

通过CO_2、环氧丙烷和马来酸酐进行三元共聚得到了一种主链含双键的马来酸酐共聚聚甲基乙撑碳酸酯(PPCMA)。~1H-NMR测得该聚合物中双键链段摩尔百分含量为4.69%。采用多个非等温扫描速率的热分析动力学方法,利用DSC的升温数据,研究了PPCMA在引发剂DCP存在下的化学交联模型。利用Friedman微分法和非线性回归分析法得到了精确的化学交联反应动力学方程和动力学参数。由该动力学方程反推出不同升温速率下的DSC曲线可以很好地再现实验结果。最后通过动力学方程推测得到某一特定反应温度下,交联程度与时间的关系图。     

液体乙烯基硅树脂的制备及固化反应动力学

合成了一种液体乙烯基硅树脂,并用FT-IR、GPC、1H NMR和29Si NMR等手段对其结构进行表征。采用非等温差示扫描量热法(DSC)研究了乙烯基硅树脂/苯基含氢硅油体系的固化反应动力学,用Kissinger方程和高级等转化率法(Vyazovkin方法)分别计算了该体系的表观活化能Ea,用Málek法进行模型拟合动力学分析,通过T--外推法确定该体系的固化工艺参数。结果表明:Kissinger法和Vyazovkin法得到的活化能分别为85.3kJ·mol-1和84.0 kJ·mol-1,二者所得结果的差别较小;乙烯基硅树脂体系固化动力学符合-esták-Berggren(m,n)模型,m和n分别为0.092、1.440,拟合曲线与实验的DSC曲线吻合;该树脂体系的近似凝胶化温度为89.1℃,固化温度为127.8℃,后处理温度157.6℃。     

Nonisothermal curing kinetics of a novel polymer containing phenylsilylene and propargyl–hexafluorobisphenol a units

A novel thermosetting polymer, poly[(phenylsilylene) propargyl–hexafluorobisphenol A] (PBAFS), with a new structure was synthesized. The structure of PBAFS and its cured resins were characterized by Fourier transform infrared spectra. During curing, a hydrosilylation reaction may occur between Si? H and C?C bonds and a Claisen rearrangement reaction of aryl propargyl ether led to formation of chromene, which immediately preceded polymerization on heating. The dynamic viscosity behavior was investigated by rheological experiment. Thermal stability of the cured PBAFS was also measured by Thermogravimetric analysis. The curing behavior of PBAFS was monitored by nonisothermal differential scanning calorimetry at different heating rates. The kinetic parameters and the kinetic model of the cure reaction were evaluated by Kissinger, Ozawa, and Friedman methods. The cure reaction of PBAFS was found nth‐order in nature and the prediction curves by Friedman method for nonisothermal curing reaction were in good agreement with the experimental curves. The isothermal curing time of PBAFS were predicted by Vyazovkin and model‐fitting methods from the nonisothermal kinetic parameters. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Cure kinetics and modeling the reaction of silicone rubber

The kinetics of the crosslinking reaction of polydimethylsiloxane (PDMS) was studied by differential scanning calorimeter (DSC). The kinetic parameters of the reaction were calculated from the Kissinger, the Ozawa, the Flynn–Wall–Ozawa, and the Friedman methods. The Chang method was also used to determine reaction order and to compare with other methods. To improve the accuracy, the autocatalytic model and the modified-Chang method were introduced. The theoretical heat generation against temperature curves, calculated by the estimated kinetic parameters, well fit the experimental data, which indicated that the analysis method used in this work was valid. The processing time and temperature was predicted by the direct integration of the kinetic equation with the data from isothermal runs. It would give a valuable guide for the thermal processing of silicone rubber.     

丁香酚环氧有机硅树脂的制备及其固化动力学研究

利用丁香酚环氧和环四硅氧烷硅氢加成得到新型生物基环氧树脂D4EUEP,通过核磁共振氢谱和飞行时间质谱表征其准确结构。使用非等温DSC对D4EUEP/33DDS固化体系进行分析,采用双参数自催化模型和Málek判据建立了该体系固化动力学模型。模型计算结果与实验结果相关系数大于99%,证明该模型可以较好地描述D4EUEP/33DDS体系的固化过程。通过AICM方法研究了体系的有效活化能与转化率之间的关系,揭示了微观反应机理的变化,并通过Vyazovkin法对D4EUEP/33DDS体系进行了等温固化预测。     

Adiabatic correction for the esterification of acetic anhydride by methanol via accurate kinetics

In the field of adiabatic correction for complex reactions, a simple one-stage kinetic model was used to estimate the real reaction kinetics. However, this assumption simplified the real process, inevitably generated inaccurate or even unsafe results. Therefore, it was necessary to find a new correction method for complex reactions. In this work, esterification of acetic anhydride by methanol was chosen as an object reaction of study. The reaction was studied under different conditions by Reaction Calorimeter (RC1). Then, Thermal Safety Software (TSS) was used to establish the kinetic model and estimate the parameters, where, activation energies for three stages were 67.09, 81.02, 73.77 kJ·mol^-1 respectively, and corresponding frequency factors in logarithmic form were 16.05, 19.59, 15.72 s^-1. In addition, two adiabatic tests were performed by Vent Sizing Package2 (VSP2). For accurate correction of VSP2 tests, a new correction method based on Enhanced Fisher method was proposed. Combined with kinetics, adiabatic correction of esterification reaction was achieved. Through this research, accurate kinetic parameters for a three-step kinetic model of the esterification reaction were acquired. Furthermore, the correlation coefficients between simulated curves and corrected curves were 0.976 and 0.968, which proved the accuracy of proposed new adiabatic correction method. Based on this new method, conservative corrected results were able to be acquired and be applied in safety assessment.     

Thermal decomposition kinetics of sodium perborate tetrahydrate to sodium metaborate by using model-fitting and model-free methods

Model-free and model-fitting methods have been applied to data for nonisothermal and isothermal decomposition of sodium perborate tetrahydrate to sodium metaborate. The kinetic triplet (f(a), A and E) of sodium perborate tetrahydrate was found by model fitting method defined with a single step reaction, which has an excellent fit for nonisothermal data and obeys different kinetic models and yields highly uncertain values of Arrhenius parameters. The isothermal and nonisothermal data for thermal decomposition of sodium perborate tetrahydrate to sodium perborate monohydrate and sodium metaborate were evaluated by model-free isoconversional method. The complex nature of multi-step process of sodium perborate tetrahydrate to sodium metaborate was more easily indicated by using wide temperature range in nonisothermal isoconversional method.     

Liquid crystalline thermosets as binder for powder coatings: Thermoanalytical study of the cure characteristics of a carboxylated main chain liquid crystalline oligoester

The curing behavior of a liquid crystalline oligoester (LCO), based on 4,4′-diacetoxybiphenyl and dodecanedioic acid, as a model resin for powder coatings, in presence of triglycidyl isocyanurate (TGIC), as a curing agent, was studied by isothermal differential scanning calorimetry (DSC). The analysis of isothermal data was performed using the model-free isoconversional method. Activation energy as a function of extent of conversion, , has been calculated by the Friedman technique. It showed an ascending trend from about 133.7 kJ/mol, at =0.1 to 177.2 kJ/mol, at =0.4, then it reached approximately a constant value of about 150±5% kJ/mol in the range of 50–90%.

The results indicated that the kinetic process does not follow a single-step curing reaction model. To verify the isothermal analysis result, we carried out further, non-isothermal differential scanning calorimetry and depolarizing transmittance measurements on the stoichiometric mixture of LCO/TGIC, at different heating rates. The results of these experiments exhibited that the kinetic process of the investigated system is strongly influenced by curing condition which alters the liquid crystalline state of the sample.     

A general kinetic model framework for the interpretation of adiabatic calorimeter rate data

Notwithstanding the variety and complexity of the reactions studied by adiabatic calorimeters like ARC, the data interpretation techniques are not general enough. Traditional thermokinetic analysis primarily lumps a complex multi-step reaction into a single overall reaction and ignores possible thermal effects in some of the possible side reactions. With detailed chromatographic/mass spectrometric analysis of the headspace gases and the condensed phase residues, the pressure profile becomes an additional source of identification of the mechanism and the kinetics of the overall reaction. Finally, in the context of new multiphase catalytic processes of greater efficiency and environment friendliness and with reference to the storage of potentially incompatible fluid mixtures in metallic containers, ARC studies of heterogeneous reaction systems are becoming part of the mandatory safety evaluations. With a few additional measurements a proper kinetic interpretation of the ARC data on such systems seems possible. The paper presents a general model that was shown to be easily adaptable to a number of published reactions of various complexities referred to above. Standard thermal hazard characteristics like the onset temperature, adiabatic temperature rise, self-heat rate, time-to-maximum rate, pressure–temperature profile, etc. could be accurately calculated by the model and these compared closely with the experimental data. It is hoped that the model would be useful as a general-purpose tool for the interpretation of adiabatic calorimetric data for the purpose of process hazard assessment.     

SEBS化学交联的热分析动力学研究

采用非等温差示扫描量热(DSC)分析法,在交联剂过氧化二苯甲酰(BPO)存在下,对部分氢化的苯乙烯-丁二烯-苯乙烯三嵌段共聚物(SEBS)的化学交联过程进行了热分析动力学研究,在不同升温速率下获得SEBS交联反应的DSC升温曲线,采用Model-free (无模型) 分析法包括Friedman、Ozawa-Flynn-Wall和Kissinger等三种方法分别对SEBS交联反应进行了热动力学分析,求出其动力学初始参数值,然后用Model-fitting (模型拟合)分析法通过选择动力学模型,采用多元非线性回归优化得到了精确的模型参数。所得动力学模型表明BPO引发的SEBS交联过程经过了三步反应,每步反应的活化能依次减少。此优化的动力学模型可用来预测不同温度下反应时间和交联度之间的关系,表明可通过控制交联温度和反应时间得到所需交联程度的SEBS产品,从而达到其性能设计的目的。     

Critical parameters for heat transfer and chemical reactions in thermosetting materials

The equations of one-dimensional heat transfer with chemical reactions with isothermal initial conditions and constant wall temperature are solved approximately for all types of kinetic models. The general solution is valid for low exothermal peaks and it is characterized explicitly by two dimensionless parameters. The first parameter is the ratio between the time scale for heat conduction and that for the chemical reaction; the second parameter is the ratio between the processing temperature and the adiabatic temperature rise. The number of additional parameters depends on the particular choice of kinetic model. The maximum temperature in the solution always occur at the center line and its magnitude is proportional to the maximum rate of reaction. For a second-order autocatalytic kinetic model, closed from results can be obtained. The solution is in this case characterized by two additional dimensionless parameters. The analytical solution agrees excellently with numerical solutions for small exothermal temperature peaks (<10% of the adiabatic temperature rise), but the qualitative agreement is very good also for cases with significant exothermal peaks. The general solution can be used also for the case when the kinetic model is unknown and only experimental DSC results are available. © 1994 John Wiley & Sons, Inc.     

Predicting thermal degradation kinetics of nylon6/feather keratin blends using artificial intelligence techniques

A multi-structured architecture of artificial intelligence techniques including artificial neural network (ANN), adaptive-neuro-fuzzy-interference system (ANFIS) and radial basis function (RBF) were developed to predict thermal degradation kinetics (TDK) of nylon6 (NY6)/feather keratin (FK) blend films. By simultaneous implementation of back-propagation ANN and feed-forward ANFIS modeling on the experimental data obtained from thermogravimetric analysis (TGA) method, thermal degradation behavior of various compositions of NY6/FK blends was successfully predicted with minimum mean square errors (MSE). RBF networks were then trained on the TGA data at one heating rate for predicting analogs information at different heating rates, providing sufficient feed for TDK modeling. According to the comparison made between experimental and predicted kinetic parameters of thermal degradation process calculated from Friedman and Kissinger methods, the proposed prediction effort could effectively contribute to the estimation of precise activation energy (E_a) and reaction order (n) values with least amount of experimental work and most accuracy.