Parametres cinetiques de systemes epoxy/acide par analyse calorimetrique differentielle (DSC)

We have studied the curing of epoxy resin diglycidylether of bisphenol A (DGEBA), by two different hardeners poly(styrene-co-acrylic acid) (SAAx) at different acid percent and poly(acrylic acid). We follow the kinetics by non-isothermal and isothermal. In non-isothermal mode the heating rates were between 2.5 and 20°C min^-1 in the temperature range of 25-250°C. The reaction was supposed to follow the n ^th order. In isothermal mode, four temperatures for each system were done. In this case the reaction was autocatalysed. The interpretation of the exotherms allowed to determine the kinetic parameters of the studied systems. This revised version was published online in August 2006 with corrections to the Cover Date.     

The mechanism and kinetics of curing reaction of AG-80/SED system by DSC

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.     

Curing Kinetics Modeling of Epoxy Modified by Fully Vulcanized Elastomer Nanoparticles Using Rheometry Method

In this study, the curing kinetics of epoxy nanocomposites containing ultra-fine full-vulcanized acrylonitrile butadiene rubber nanoparticles (UFNBRP) at different concentrations of 0, 0.5, 1 and 1.5 wt.% was investigated. In addition, the effect of curing temperatures was studied based on the rheological method under isothermal conditions. The epoxy resin/UFNBRP nanocomposites were characterized via Fourier transform infrared spectroscopy (FTIR). FTIR analysis exhibited the successful preparation of epoxy resin/UFNBRP, due to the existence of the UFNBRP characteristic peaks in the final product spectrum. The morphological structure of the epoxy resin/UFNBRP nanocomposites was investigated by both field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) studies. The FESEM and TEM studies showed UFNBRP had a spherical structure and was well dispersed in epoxy resin. The chemorheological analysis showed that due to the interactions between UFNBRP and epoxy resin, by increasing UFNBRP concentration at a constant temperature (65, 70 and 75 °C), the curing rate decreases at the gel point. Furthermore, both the curing kinetics modeling and chemorheological analysis demonstrated that the incorporation of 0.5% UFNBRP in epoxy resin matrix reduces the activation energy. The curing kinetic of epoxy resin/UFNBRP nanocomposite was best fitted with the Sestak–Berggren autocatalytic model.     

Study on curing of novolac epoxy resin

The optimization of proportions of novolac epoxy resin, Dobeckot E4 and polyamide hardener, EH411 has been established by DSC and the data indicates that resin-polyamide, 100∶40 and 100∶50, appear to be optimum where ‘extent of cure’ is maximum. The kinetic parameters for these formulations have been evaluated using isothermal and dynamic modes by employing DSC. The rate constants have been evaluated for curing process of these formulations using isothermal DSC mode in the temperature range of 70°–90°C. These have also been predicted at 20°±1°C (room temperature) by extrapolating the data obtained at elevated temperatures. A comparison of the predicted values with the experimental values shows that there is a good agreement between them.     

Study of the thermal degradation of bioactive sol–gel coatings for the optimization of its curing process

A set of materials has been prepared by sol–gel process containing different quantities of hydroxyapatite (0, 2.5 and 5% HAp w/w) using as silica precursors glycidyloxypropyltrimethoxysilane (GPTMS) and triethoxyvinylsilane (VTES). In order to optimize the curing process to obtain sintherized systems (inorganic network) or hybrid systems (organic–inorganic) a TG and FTIR studies have been developed and degradation kinetic triplet parameters were obtained (the activation energy, pre-exponential factor, and function of degree of conversion). The kinetic study was analyzed by means of an integral isoconversional non-isothermal procedure (model free), and the kinetic model was determined by the Coats–Redfern method and through the compensation effect (IKR). All the systems followed the n = 6 kinetic model. The addition of HAp increases the thermal stability of the systems. The isothermal degradation was simulated from non-isothermal data, and the curing process could be defined to obtain the two types of materials. Temperature under 250 °C allows the formation of hybrids networks.     

Synthesis and cure kinetics of diphenyl(diphenylethynyl)silane monomer

Diphenyl(diphenylethynyl)silane ((ph–C≡C)₂–Si–ph₂) (DPDPES) was synthesized by the Grignard reaction. The corresponding isothermal and non-isothermal cure kinetics of DPDPES were analyzed by using differential scanning calorimetry (DSC), and the molecular structure was characterized by H-NMR. The results showed that all the cure curves were typically sigmoid shape and cure reactions could be described by an autocatalytic kinetic model by isothermal DSC. The kinetic data, for example, activation energy (E) and frequency factor (A), were 119.22 kJ/mol and 4.67 × 10⁷ (s^?1), respectively. The non-isothermal DSC analyses showed that E and A were 162.12 kJ/mol and 1.32 × 10⁹ (s^?1), respectively, and the reaction order was 0.94. Based on the research work of this paper, it can be said that the cure reaction of DPDPES monomer was of autocatalytic and diffusion-controlled characteristics, and the effect of the diffusion was more evident at low temperature. The cure reaction of DPDPES was a first-order kinetic reaction.     

Curing of alkyds based on semi-drying oils with melamine resin

An alkyd/melamine resin mixtures are mainly used in industrial baking enamels. The aim of this work was to study the curing behaviour of alkyds based on dehydrated castor oil and soybean oil with melamine resin by differential scanning calorimetry (DSC). The kinetic parameters obtained by the transformation of dynamic DSC results into isothermal data through Ozawa kinetic model are in good agreement with those determined by the isothermal DSC experiments. The apparent degree of curing, determined by DSC measurements and sol/gel method, has a pronounced effect on the hardness of the resultant coating film.     

Curing kinetics of arylamine-based polyfunctional benzoxazine resins by dynamic differential scanning calorimetry

In this study, the curing kinetics of polyfunctional benzoxazine resins based on arylamine, i.e. aniline and 3,5-xylidine, designated as BA-a and BA-35x, respectively, were investigated. Non-isothermal differential scanning calorimetry (DSC) at different heating rates is used to determine the kinetic parameters and the kinetic models of the curing processes of the arylamine-based polyfunctional benzoxazine resins were proposed. Kissinger, Ozawa, Friedman, and Flynn-Wall-Ozawa methods were utilized to determine the kinetic parameters of the curing reaction. BA-a resin shows only one dominant autocatalytic curing process with the average activation energy of 81-85 kJ mol⁻¹, whereas BA-35x exhibits two dominant curing processes signified by the clear split of the curing exotherms. The average activation energies of low-temperature curing (reaction (1)) and high-temperature curing (reaction (2)) were found to be 81-87 and 111-113 kJ mol⁻¹, respectively. The reaction (1) is found to be autocatalytic in nature, while the reaction (2) exhibits nth-order curing kinetics. In addition, the predicted curves from our kinetic models fit well with the non-isothermal DSC thermogram.     

酚醛树脂/蒙脱土纳米复合材料的制备及固化反应动力学研究

利用自制的有机蒙脱土 ,采用浇模固化成型法制备酚醛树脂 /六次甲基四胺 /蒙脱土纳米复合材料 ,并用XRD观察有机蒙脱土分别在热塑性和热固性酚醛树脂中复合行为 .研究发现 ,由于两种树脂的固化反应机理不同 ,热固性酚醛树脂与蒙脱土复合 ,可得插层型纳米复合材料 ;而采用热塑性酚醛树脂进行固化 ,则得到部分剥离的纳米复合材料 .通过DSC进一步研究热塑性酚醛树脂 /蒙脱土复合体系的固化反应动力学 .运用Kissinger ,Flynn Wall Ozawa ,Crane方法求出活化能和反应级数等动力学参数 .结果发现 ,加入蒙脱土使固化反应活化能下降 ,反应级数减小 ,从而有利于固化工艺的实现 ,便于纳米复合材料实际应用 .     

Influence of the addition of erbium and ytterbium triflates in the curing kinetics of a DGEBA/<Emphasis Type="Italic">o</Emphasis>-tolybiguanide powder mixture

Solid bisphenol-A epoxy resin (DGEBA) of medium molecular mass was cured using o-tolylbiguanide (TBG) as cross-linking agent. In order to improve the kinetics of the reactive system, two Lewis acid catalysts (erbium(III) and ytterbium(III) trifluoromethanesulfonates) were added in proportions of 1 phr. The kinetic study was performed by dynamic scanning calorimetry (DSC) and the complete kinetic triplet (E, A and g(α)) determined. The kinetic analysis was performed with an integral isoconversional procedure (model-free), and the kinetic model was determined by the Coats-Redfern method and through the compensation effect (IKR). All the systems followed the m=1.5/n=0.5 isothermal curing model simulated from non-isothermal experiments. The addition of a little proportion of ytterbium or erbium triflates accelerated the curing process. In order to extract further information about the role of the lanthanide triflates added to epoxy/TBG systems, the kinetic results were compared with our previous kinetic studies made on DGEBA/lanthanide triflates initiated systems.     

Thermoplastic-modified epoxy resins cured with different functionalities amine mixtures. Kinetics and miscibility study

The kinetics of a poly(methyl methacrylate) (PMMA)-modified epoxy resin cured with different functionalities amine mixtures was analyzed using differential scanning calorimetry (DSC) in both isothermal and dynamic conditions. A delay in the reaction rate was observed which increased with PMMA content. An approach of kinetic features involved in curing was carried out. A linear dependence of preexponential factors of neat systems with modifier content was considered. The approach shows the contribution of other factors including the dilution effect of the functional groups to the observed delay. Fourier transform infrared spectroscopy (FTIR) indicated a noticeable change in the interactions present in neat systems due to the presence of PMMA. On the other hand, a significant influence of the ratio between each amine in the epoxy/amine mixtures on the final physical appearance was observed. At constant curing conditions, materials from completely opaque (phase separated) to transparent (miscible) were obtained with the increase in monoamine content.     

Addition effect of erbium(III) trifluoromethanesulfonate in the homopolymerization kinetics of a DGEBA resin

Solid bisphenol-A epoxy resin of medium molecular weight was cured using a Lewis acid initiator (erbium(III) trifluoromethanesulfonate) in three different proportions (0.5, 1 and 2 phr). A kinetic study was performed in a differential scanning calorimeter. The complete kinetic triplet was determined (activation energy, pre-exponential factor, and integral function of the degree of conversion) for each system. A kinetic analysis was performed with an integral isoconversional procedure (model-free), and the kinetic model was determined both with the Coats-Redfern method (the obtained isoconversional E value being accepted as the effective activation energy) and through the compensation effect. All the systems followed the same isothermal curing model simulated from non-isothermal ones. The “nucleation and growth” Avrami kinetic model A_3/2 has been proposed as the polymerization kinetic model. The addition of initiator accelerated the reaction having higher influence when low temperatures were applied.     

2-乙基-4-甲基咪唑固化环氧树脂体系动力学模型

由2-乙基-4-甲基咪唑(2,4-EMI)固化双酚A二缩水甘油醚型环氧树脂(DGEBA)的等温差示扫描量热(DSC)实验结果发现固化反应分两阶段进行,催化聚合反应有一诱导期.由DSC测试结果求得催化聚合反应的速率常数.从反应机理出发,以诱导期为边界,建立两阶段的微观固化动力学模型.从扩散的角度在模型中引入临界固化度(αc)和扩散因子,进一步建立扩散控制固化动力学模型,对不同2,4-EMI含量和固化温度(Tc)的体系,计算得到αc.研究发现扩散因素对固化动力学影响较大,固化反应前期由化学动力学控制,后期由扩散因素控制;αc主要由体系的玻璃化转变决定,Tc越高,体系玻璃化转变时对应的固化度越大,cα越大.     

The effects of glass beads and silane treatments on the curing behavior of a brominated epoxy resin: DSC analyses

The curing characteristics of a brominated epoxy resin/dicyandiamide (DICY) system filled with silane-treated glass beads are studied using isothermal differential scanning calorimetry (DSC). Three different silane coupling agents, N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane, N-[2-(vinylbenzylamino)-ethyl]-3-aminopropyl-trimethoxysilane, and 3-glycidoxypropyl-trimethoxysilane, are applied. It is found that the reaction heats of the epoxy system are little affected by the curing temperature and the untreated glass fillers, but changed with the addition of silane-coated glass beads. The effect of glass beads on the curing reaction is more significant at the low curing temperature and conversion. The silane treatment results in changes in T_g, activation energy, reaction heat, reaction rate, and reaction order. Three silanes respond differently because of their differences in the activated reaction with the matrix system. Regardless of the various curing mechanisms involved, a simple kinetic expression can describe the curing extent at 170 and 180°C with a good accuracy for all systems studied. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2063–2071, 1997     

Cure Kinetics of DGEBA with Hyperbranched Poly （3-hydroxyphenyl） Phosphate as Curing Agent Studied by Non-isothermal DSC

IntroductionEpoxy resins are widely used in the fields of coa-tings,adhesives,insulating materials,etc..Diglycidylether of bisphenol A(DGEBA)is the most importantepoxy resin in industry because of its fluidity,physicaland mechanical properties after cure,…     

FTIR法研究乙酸酚醛酯固化邻甲酚环氧树脂的反应动力学

用ＦＴＩＲ原位测量技术研究了乙酸酚醛酯与邻甲酚环氧树脂在２－甲基咪唑存在下进行恒温固化反应的动力学，测定了固化反应的动力学参数，研究结果表明，固化反应是按照一级固化反应动力学进行的，根据羰基峰在固化反应前后的变化对固化反尖机理进行了初步探讨。     

Curing reaction of biphenyl epoxy resin with different phenolic functional hardeners

The investigation of cure kinetics and relationships between glass transition temperature and conversion of biphenyl epoxy resin (4,4′-diglycidyloxy-3,3′,5,5′-tetramethyl biphenyl) with different phenolic hardeners was performed by differential scanning calorimeter using an isothermal approach over the temperature range 120–150°C. All kinetic parameters of the curing reaction including the reaction order, activation energy, and rate constant were calculated and reported. The results indicate that the curing reaction of formulations using xylok and dicyclopentadiene type phenolic resins (DCPDP) as hardeners proceeds through a first-order kinetic mechanism, whereas the curing reaction of formulations using phenol novolac as a hardener goes through an autocatalytic kinetic mechanism. The differences of curing reaction with the change of hardener in biphenyl epoxy resin systems were explained with the relationships between T_g and reaction conversion using the DiBenedetto equation. A detailed cure mechanism in biphenyl-type epoxy resin with the different hardeners has been suggested. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 773–783, 1998     

Properties of methyltetrahydrophthalic anhydride‐cured epoxy resin modified with MITU

Methylimidazole‐terminated chain‐extended urea (MITU) containing polypropylene oxide spacer was synthesized and employed to modify epoxies composed of a diglycidyl ether of bisphenol‐A (E‐51) and methyltetrahydrophthalic anhydride (MTHPA). The curing behavior, viscoelastic property, impact response, and fracture surface morphology of the curing systems were systematically investigated. Differential scanning calorimeter (DSC) analysis reveals that the curing reactivity of the epoxy system is greatly enhanced with the addition of MITU. From the dynamic mechanical analysis, besides the low‐temperature β relaxation, shoulder at higher temperature side appears for the MITU‐modified systems. Meanwhile, the addition of MITU leads to the increase of loss factor (tan δ) over the temperature range of 0–75°C. Impact tests show that the modifier can be effective in toughening the epoxy resin at relatively low loading, and the scanning electron microscope (SEM) images of the fracture surface for the modified systems display signs of ductility. Copyright © 2008 John Wiley & Sons, Ltd.     

Investigation of cure kinetics of epoxy resin/organic montmorillonite system by differential scanning calorimetry

The cure kinetics of the epoxy resin (EP)/organic montmorillonite, with 4-diamino diphenyl methane (DDM) as curing agent, was studied by non-isothermal differential scanning calorimetry (DSC) at four linearly programmed heating rates of 5, 10, 15, and 20 deg/min, and the effects of original montmorillonite (OMMT) on cure kinetics of epoxy resin were investigated. A two parameter (m, n) autocatalytic model was used to describe the cure kinetics of the epoxy resins. The kinetic parameters were calculated with the Malek method and the curves obtained by the Málek method showed a good agreement with experimental data for EP/DDM and EP/DDM/OMMT systems. The results, based on the isoconversional method showed that the activation energy was obvious difference with the addition of OMMT in the early stages of the cure, which indicated that the OMMT have catalytic effect on the epoxy ring-opening.