Study of cure kinetics of epoxy-silica organic-inorganic hybrid materials

Cure kinetics of organic-inorganic hybrids based on epoxy resin was investigated, using differential scanning calorimetry (DSC). Thermoset hybrid materials were prepared from diglycidyl ether of bisphenol A (DGEBA) as organic precursor, and 3-glycidyloxypropyltrimethoxysilane (GLYMO) as inorganic precursor. Precursors were polymerised simultaneously using poly(oxypropylene)diamine (Jeffamine D230) as a curing agent. Isothermal DSC characterisation of DGEBA/Jeffamine system and two hybrid DGEBA/GLYMO/Jeffamine systems, with DGEBA and GLYMO mixed in mass ratios of 2:1 and 1:1, respectively, was performed at different temperatures. Applicability of empirical models, commonly used to describe the curing kinetics of thermosets, to hybrid systems was investigated, and the resulting parameters were tested on dynamic DSC scans. Additionally, prepared materials were studied by FTIR and the extraction in tetrahydrofuran. The presence of inorganic phase was found to hinder complete cross-linking of organic phase and influence the kinetics of cure.     

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,…     

The effect of zeolite on the curing of epoxy resin by polyaniline: a kinetic study

Polyaniline sulfate‐zeolite composite was prepared by emulsion polymerization. Epoxy resin was cured using polyaniline‐sulfate salt and various amounts of polyaniline sulfate‐zeolite composite. The kinetics of the cure reaction for an epoxy resin based on the diglycidyl ether of bisphenol A (DGEBA) with polyaniline‐sulfate and polyaniline sulfate‐zeolite composite have been studied using differential scanning calorimetry (DSC) under isothermal and dynamic conditions. Isothermal kinetics analysis was performed using the phenomenological model of Kamal. Dynamic kinetic analysis was performed using Kissinger's method. Copyright © 2002 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.     

Kinetic studies of the effect of ABS on the curing of an epoxy/cycloaliphatic amine resin

Using differential scanning calorimetry (DSC), we have studied, under isothermal and dynamic conditions, the kinetics of the cure reaction for an epoxy resin based on the diglycidyl ether of bisphenol A (DGEBA) modified with different contents of acrylonitrile–butadiene–styrene (ABS) and cured with 1,3‐bisaminomethylcyclohexane (1,3‐BAC). Kinetic analysis were performed using three kinetic models: Kissinger, Flynn–Wall–Ozawa, and the phenomenological model of Kamal as a result of its autocatalytic behavior. Diffusion control is incorporated to describe the cure in the latter stages, predicting the cure kinetics over the whole range of conversion. The total heats of reaction were not influenced by the presence of ABS. The autocatalytic mechanism was observed both in the neat system as well as in its blends. The reaction rates of the blends and the maximum conversions reached did not change too much with the ABS content. Blending ABS within the epoxy resin does not change the reaction mechanism of the epoxy resin formation. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 351–361, 2000     

Cure kinetics of liquid crystalline epoxy resins based on biphenyl mesogen

The cure kinetics of a biphenyl-based liquid crystalline (LC) epoxy resin (LCER) was studied using differential scanning calorimetry (DSC) and polarized optical microscopy. The effects of LC phase formation on the cure kinetics were investigated. Both a model-free isoconversional method and a model-fitting method were used to analyze the DSC data. Results from the isoconversional analysis were applied to develop tentative multi-step kinetic models describing the curing reaction. Kinetic analysis showed that compared to the resins cured in amorphous phase, LCERs exhibited higher values of reaction enthalpy and a complex dependence of activation energy on the degree of cure. The formation of the LC phase resulted in a decrease in activation energy, leading to higher degree of reaction.     

Kinetics of polymerization of epoxy adhesives and composites

The polymerization kinetics of epoxy materials are examined with particular emphasis in assessing (i) the proper use of non-isothermal DTA or DSC data, (ii) the correlation between glass transition temperature and cure degree, (iii) the effect of the filling agent on the phenomenological kinetics of the cure process.     

酸酐固化环氧树脂/蒙脱土复合材料的等温固化动力学

用等温差示扫描量热法(DSC)研究了酸酐固化环氧树脂/蒙脱土复合材料的等温固化过程，考察了未处理的蒙脱土(MMT)和有机蒙脱土(OMMT)对环氧树脂固化动力学的影响. 实验表明， 环氧树脂的固化过程包含自催化机理，加入蒙脱土没有改变固化反应机理. 用Kamal方程对该体系的固化过程进行拟合，得到反应级数m、n，反应速率常数k1、k2，总反应级数(m + n)在2.4～3.0之间. MMT的加入使环氧树脂体系的k1、k2有所降低，而OMMT的加入对体系的k1、k2影响较为复杂，加入蒙脱土对环氧树脂固化体系的活化能影响较小.     

Characterization of epoxy prepreg SPX 8800 system by isothermal differential scanning calorimetry

Isothermal Differential Scanning Calorimetry (DSC) was used to study the curing behavior of epoxy prepreg SPX 8800 system, which contains DGEBA/DICY/Diuron (Diglycidyl ether of bisphenol A/Dicyandiamide/Diuron) reinforced by three layers of glass fibre. The rate curves from the DSC study agreed well with those obtained from the isothermal FT Near Infrared (FTNIR) study and similar activation energy was obtained in the range of 92.6 to 87.7 kJ/mol up to 50% total conversion. Modelling of the whole DSC trace with empirical equation dx/dt=kx^m(A-x)ⁿ gave relatively good fitting of the experimental curves (the error is lower than 15%.) in the whole studied cure temperature range (75-110°C) and no significant difference in cure kinetics was observed for both epoxy prepreg and neat resin.     

热塑性/热固性聚合物共混体系研究——乙炔端基砜/聚砜共混物的动态固化动力学

近年来,半互穿聚合物网络(SIPN)概念被用来研制能结合热塑性聚合物的加工性和热固性聚合物的高温性能的大分子体系,用于复合材料耐高温树脂基体。例如:乙炔端基酰亚胺低聚物与热塑性聚酰亚胺基SIPN,线性聚酰亚胺与热固性双马来酰亚胺基SIPN以及热塑性树脂与双腈基SIPN已有报道。研究结果表明共混物起到协同作用,易于加工并具有优异的性能。乙炔端基砜(ATS)树脂具有与聚砜树脂相类似的结构,被认为在将来代替环氧用于高性能粘合剂和复合材料树脂基体的候选者之一。其另     

DSC study on the effect of isocyanates and catalysts on the HTPB cure reaction

The urethane forming cure reactions of hydroxyl terminated polybutadiene (HTPB) binder with three different isocyanate curatives, viz., toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) and 4,4-methylene bis(cyclohexyl isocyanate) (MCHI), were investigated by differential scanning calorimetry (DSC). The effect of two cure catalysts, viz., dibutyl tin dilaurate (DBTDL) and ferrric tris-acetylacetonate (FeAA) on the cure reactions was also studied. Cure kinetics was evaluated using the multiple heating rate Ozawa method. The reactivities of the three isocyanates and catalytic efficiencies were compared based on the DSC reaction temperatures, activation energies and rate constants. Viscosity build-up in these systems at isothermal temperature was also studied and compared with the results from DSC.     

热塑性/热固性聚合物共混体系研究——乙炔端基砜/聚砜共混物的动态固化动力学

The dynamic cure kinetics of thermosetting acetylene-terminated sulfone (ATS) and two blends prepared by the ATS and thermoplastic bisphenol A polysulfone (PSF), polyary-lethersulfone with cardo group (PES-C) were determinated by differential scanning calori-metry (DSC). The addition of polysulfone's resin increases the temperature of initial reaction and decreases the activation energy of cure reaction(E), pre-exponnential factor (LnA), and heat of cure reaction (AH). The temperature of reaction peak and final reaction and the reaction order(n) have been no effect.     

Cure Kinetics Study of Two Epoxy Systems with Fourier Tranform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC)

This work was aimed at the study of cure kinetics of two commercial thermosetting epoxy systems, Epikote resin 816 LV/Epikure F205 and Epikote resin 240/Epikure F205, by Fourier Tranform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). The studied systems consist of a resin (A), based on a diglycidyl ether of bisphenol A and a hardener (B) based on the Isophorodiamine (IPDA) a cycloaliphatic diamine. These systems are used for the building and civil engineering industries, e.g. flooring compounds, adhesives, mortars and grouts. FTIR spectroscopy was employed to investigate the isothermal curing kinetics at 30, 50 or 70°C and DSC analysis to study the non-isothermal curing kinetics at different heating rates 2.5, 5, 10 and 20°C/min, from 20 to 300°C. A kinetic model was employed to simulate the FTIR isothermal experimental data using two kinetic rate constants and incorporating also diffusion control at high degrees of conversion. Finally, the variation of the effective activation energy with the extent of curing was estimated using isoconversional analysis of non-isothermal DSC data.     

气相生长碳纤维对环氧树脂固化反应的影响及其复合物固化动力学研究

用示差扫描量热方法研究了气相生长碳纤维作为填料对4,4′-二氨基二苯甲烷四缩水甘油环氧树脂(TGDDM)/4,4′-二氨基二苯基砜(DDS)等温固化反应的影响.与纯环氧树脂一样,气相生长碳纤维复合物的固化反应也属于自催化反应类型.气相生长碳纤维对环氧树脂的固化反应动力学影响很小.固化反应的过程可以用一种修正过的自催化动力学模型来描述,在整个固化反应过程中纯TGDDM/DDS环氧树脂及其气相生长碳纤维复合物模型拟合得到的结果和实验数据相当一致.     

Isothermal cure kinetics of epoxy/phenol‐novolac resin blend system initiated by cationic latent thermal catalyst

The investigation of the cure kinetics of a diglycidyl ether of bisphenol A (DGEBA)/phenol‐novolac blend system with different phenolic contents initiated by a cationic latent thermal catalyst [N‐benzylpyrazinium hexafluoroantimonate (BPH)] was performed by means of the analysis of isothermal experiments using a differential scanning calorimetry (DSC). Latent properties were investigated by measuring the conversion as a function of curing temperature using a dynamic DSC method. The results indicated that the BPH in this system for cure is a significant thermal latent initiator and has good latent thermal properties. The cure reaction of the blend system using BPH as a curing agent was strongly dependent on the cure temperature and proceeded through an autocatalytic kinetic mechanism that was accelerated by the hydroxyl group produced through the reaction between DGEBA and BPH. At a specific conversion region, once vitrification took place, the cure reaction of the epoxy/phenol‐novolac/BPH blend system was controlled by a diffusion‐control cure reaction rather than by an autocatalytic reaction. The kinetic constants k₁ and k₂ and the cure activation energies E₁ and E₂ obtained by the Arrhenius temperature dependence equation of the epoxy/phenol‐novolac/BPH blend system were mainly discussed as increasing the content of the phenol‐novolac resin to the epoxy neat resin. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2945–2956, 2000     

Cure reaction and phase behavior of liquid crystalline epoxides-anhydride systems

A series of novel liquid crystalline epoxides with lateral substituents were cured with anhydrides and the cure kinetics was investigated by non-isothermal DSC technique. The results showed that the lengths of lateral substituents have great effect on the value of Ea. The curing reaction became less active, when the liquid crystalline epoxides have long lateral substituents and were controlled by diffusion at the late stage of cure. A nematic structure was observed by POM and XRD.     

Modeling the curing kinetics for a modified bismaleimide resin

The kinetics of curing for a modified bismaleimide (BMI) has been investigated to ascertain a suitable cure model for the material. The experimental data for characterizing the curing kinetics for a modified bismaleimide resin were determined using a DSC isothermal scan method and indicated a curing mechanism involving multiple reactions. The reaction process was shown to be dominated by a different mechanism at different stages of the cure process, with an initial autocatalytic reaction shifting into an nth order reaction as the reaction proceeded. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 907–913, 2000     

Epoxy polymers: effect of the elastomee in the kinetics of polymerization

The polymerization kinetics of three epoxy adhesives HX-205, HX-206 and F-185 was defined by means of thermal analysis techniques (DSC and TMA).It was found that the liquid carboxy-terminated butadiene acrylonitriles (CTBN) and the solid rubber elastomer present in HX-206 and F-185 do not affect the phenomenological kinetics of the isothermal cure process by comparison with HX-205, which contains the same epoxy but no elastomer.It was also found that the isothermal (373 K) cure of these adhesives follows a two-range behaviour, i.e., the phenomelogical order of the cure kinetics is close to zero before and close to one after a “critical” time of cure.The trend of the glass transition temperature T_g vs the cure degree α for HX-206 and F-185 was always below that for HX-205.T_g did not approach the temperature of cure t_c for α = 1 for elastomer-added adhesives, whereas HX-205 displayed an almost liear trend, with e.g. T_g = 87° C for α. = 85%.