共查询到20条相似文献,搜索用时 15 毫秒
1.
Belén Montero Carmen Ramírez Maite Rico Luis Barral Javier Díez Joaquín López 《Polymer International》2010,59(1):112-118
Polyhedral oligomeric silsesquioxanes (POSS®) can be added to thermoplastic and thermostable polymers to obtain hybrid materials with only a minor tendency to suffer ignition. The aim of the work reported was to analyse the influence of an octafunctional POSS® in the pyrolysis of an epoxy/amine system as well as during the combustion process. Thermal degradation of the modified materials, with respect to the unmodified ones, was analysed using thermogravimetric analysis. As the content of POSS® increased the stability improved and the char/ceramic yields were higher. The Kissinger–Akahira–Sunose method was applied to the modified blends and it showed a decrease in the activation energy with POSS® content. Empirical kinetic models, as well as generalized master plots, were applied to explain the degradation mechanism for ternary blends. The limiting oxygen index parameter was measured to analyse the fire retardancy effect of POSS®: it increased from 24.3 to 25.4% with the addition of 2.5 wt% of POSS®. The mechanism of thermal degradation of the hybrid materials based on an epoxy resin is affected by the presence of the octaepoxy POSS®. Only small amounts of POSS® are necessary to enhance the combustion resistance of the system. Copyright © 2009 Society of Chemical Industry 相似文献
2.
采用非等温DSC法对低黏度体系CY184/IPDA环氧树脂体系及对CY184/ES184/IPDA环氧/环硫树脂体系的固化反应动力学进行了研究。用高级等转化率Vyazovkin积分法求取活化能Ea,通过Málek法确定了固化反应机理函数和动力学参数,得到固化反应动力学方程。结果表明:CY184/IPDA环氧树脂体系的平均活化能为47.04 kJ·mol-1;CY184/ES184/IPDA环氧/环硫树脂体系的活化能为48.97 kJ·mol-1。两种体系的模型拟合曲线与实验得到的DSC曲线吻合得较好,均符合esták-Berggren(m,n)模型。 相似文献
3.
Tsuneo Koike 《应用聚合物科学杂志》1992,44(4):679-690
The isothermal curing behavior of an epoxy resin system has been monitored by a dielectric measurement whose sensor consisted of a vertical parallel-plate cell based on a three-terminal method. The materials used in the isothermal cure were the diglycidyl ether of bisphenol-A (DGEBA), which was purified from Epon 825 by recrystallization, and 4,4′-diamino diphenyl methane (DDM). A dielectric relaxation was observed during each isothermal cure at temperatures of 70,80,90, and 100°C, which were below the glass transition temperature (Tg) of the reactive DGEBA–DDM system at the gel point. The relaxation is considered to be caused by the transformation from a liquid state to an ungelled glassy state as a result of an increase in molecular weight because gelation followed by a rubbery state did not exist in the temperature range studied. The dielectric relaxation for the DGEBA–DDM system fits the empirical model of the Havriliak–Negami equation. The Tg of the DGEBA–DDM system, which was estimated from the dielectric relaxation time, agreed with the one experimentally determined by differential scanning calorimetry (DSC). 相似文献
4.
Richard A. Pethrick Elisabeth A. Hollins Lain McEwan A. Pollock David Hayward Peter Johncock 《Polymer International》1996,39(4):275-288
Dielectric and rheological measurements are reported on the effect of cure temperature on the water absorption of tris[(2,3-epoxypropoxy)phenyl] methane cured with a 1 : 1 stoichiometric ratio of 4,4′-diaminodiphenylsulphone. Analysis of the water absorption characteristics of these materials using a combination of dielectric and gravimetric measurements has indicated that water molecules can be found in two distinctly different types of environments. There are water molecules which are strongly interacting with polar groups and water molecules clustered together into sub-micro-scale cavities within the matrix structure. Changes in the final cure temperature have the effect of changing both the extent and distribution of the types of water molecules present in the matrix. Validation of the diffusion coefficients obtained from the dielectric analysis is based on a comparison with gravimetric data and the implications are discussed. Differences observed between these two different types of measurement are related to peculiarity in the dielectric method and its extreme sensitivity to interfacial phenomena. 相似文献
5.
Rotational molding is a new process for thermosets, few research works have been done on this subject. The goal of this study is to determine the optimal conditions (time, temperature, viscosity, etc) of this process for an epoxy-amine system. The thermal and rheological analysis help us to investigate the vitrification and the gelation of the reactive system (DGEBA-DETDA) and to draw the TTT diagram. We have completed this diagram by adding the isoviscosity curves to determine the available domain for rotational molding. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
6.
Summary. The effect of amine/epoxy ratio on the fracture toughness (KIc) of tetrafunctional epoxy resin was investigated. KIc value was measured by single-edge notch-bend test. The KIc value of the tetrafunctional epoxy resin increased with increasing the amount of amine curing agent. This result was explained
with the structural viewpoint of the epoxy network. The network structure of the tetrafunctional epoxy was analyzed with dynamic
thermomechanical measurement and in-situ near IR technique.
Received: 19 June 1997/Accepted: 17 Juli 1997 相似文献
7.
Filiberto González Garcia Maria Elena LeyvaAlvaro Antonio Alencar de Queiroz Alexandre Zirpoli Simões 《International Journal of Adhesion and Adhesives》2011,31(4):177-181
The mechanical and adhesives properties of epoxy formulations based on diglycidyl ether of bisphenol A cured with various aliphatic amines were evaluated in the glass state. Impact tests were used to determine the impact energy. The adhesive properties have been evaluated in terms single lap shear using steel adherends. Its durability in water at ambient temperature (24 °C) and at 80 °C has also been analyzed. The fracture mechanisms were determined by optical microscopy. It was observed a strong participation of the cohesive fracture mechanisms in all epoxy system studied. The 1-(2-aminoethyl)piperazine epoxy adhesive and piperidine epoxy adhesive presents the best adhesive strength and the largest impact energy. The durability in water causes less damage to piperidine epoxy networks. This behavior appears to be associated with the lower water uptake tendency of homopolymerised resins due to its lower hydroxyl group concentration. 相似文献
8.
The present study was carried out to determine the effect of carbon black (CB) nanofiller silanization and loading on isothermal curing kinetics of epoxy nanocomposites. The epoxy resin specimens incorporated with 2, 4, and 8 wt% pristine CB and silanized CB were cured at isothermal temperatures of 43, 60, and 104°C. Differential scanning calorimetry was used to characterize the curing kinetics, Fourier transform infrared spectroscopy was employed to confirm silanization of CB nanofillers, and scanning electron microscopy was utilized to study the morphology of nanocomposite specimens. It was also observed that the silanization did not change the curing kinetics of CB nanocomposites significantly as compared to the neat epoxy resin. However, the curing reactions of the pristine CB nanocomposites were slower than the neat epoxy resin marked by an average 10 and 4% decrease in the final degree of cure for the nanocomposite specimens cured at 43 and 60°C, respectively. The morphological studies revealed that the silanized CB particles exhibited a more stable and homogeneous dispersion in the epoxy resin than the pristine CB particles. Potential applications for the fabricated nanocomposites include sensors, actuators, and conductive coatings for electrostatic dissipation control in plastic parts. 相似文献
9.
The erasure below the glass‐transition temperature (Tg) of the effect of isothermal physical aging (at aging temperature Ta) in a fully cured epoxy/amine thermosetting system is investigated using the torsional braid analysis (TBA) dynamic mechanical analysis technique and the differential scanning calorimetry (DSC) technique. From the TBA temperature scans, the intensity of the localized perturbation of the moduli in the vicinity of the Ta (90°C), due to isothermal physical aging, is decreased by heating to below the Tg (Tg∞ = 177°C), indicating that the physical aging effect can be eliminated by heating to below the Tg. The isothermal aging effect in the vicinity of the Ta is almost completely eliminated by heating to 50°C above the Ta (i.e., 140°C); however, a competing aging effect occurs above Ta at higher temperatures during the heating. Erasure below Tg of the isothermal physical aging effect is inferred from DSC experiments from the diminished relaxation enthalpy in the vicinity of the Tg, which is measured from the difference in areas between the aged (Ta = 150°C) and deaged thermograms. A comparison of the TBA and DSC results is made. Implications on the heterogeneous nature of the amorphous glassy state of polymers are discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 396–404, 2001 相似文献
10.
Sue Ann Bidstrup Norman F. Sheppard Stephen D. Senturia 《Polymer Engineering and Science》1989,29(5):325-328
A low molecular weight epoxy resin is cured isothermally with an aromatic amine hardener, and the dielectric properties are measured as a function of the frequency, reaction time, and cure temperature. At specific stages in the cure, small samples from the reacting mixture are quenched and subsequently analyzed for the glass transition temperature and epoxy group conversion by differential scanning calorimetry. In this manner, the change In dielectric properties can be directly correlated with the network structure. The ionic conductivity is modeled as a function of the cure temperature and the cure-dependent glass transition temperature using a Williams-Landel-Ferry (WLF) relation. Combining this WLF relation with the DiBenedetto equation, a comprehensive model relating conductivity with the extent of reaction and cure temperature has been developed. 相似文献
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12.
The reactions between a multifunctional epoxy resin, tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) and a monofunctional amine, methylaniline (mAnil) are studied. Due to the existence of a tertiary amine catalytic center within the TGDDM molecule, the etherification reaction during cure of TGDDM is usually more significant than in other epoxide systems. The importance of this reaction relative to the amine addition reactions is investigated. In situ near-infrared spectroscopy is used to obtain kinetic data during the cure reactions. The reaction rate constants are calculated from linear regression analysis for both amine addition and etherification reactions based on the reaction mechanisms proposed. Arrhenius relationships are observed for all the reaction rate constants involved. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:895–901, 1998 相似文献
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14.
酚醛胺/环氧树脂胶粘剂耐化学介质性能研究 总被引:1,自引:1,他引:0
以自制酚醛胺作为环氧树脂(EP)的固化剂,研究了酚醛胺/EP胶粘剂的耐化学介质性能和耐久性。结果表明:酚醛胺/EP胶粘剂在水、10%NaOH和2%NaCl溶液中浸泡48 h时,其剪切强度分别为6.61、4.66、5.12 MPa,其强度保留率分别为87.90%、61.97%、68.09%;酚醛胺/EP胶粘剂既具有良好的耐水性、耐碱性和耐盐性,又具有较好的碱、盐耐久性,可作为特种胶粘剂——水下胶粘剂广泛用于房屋、水利、地下建筑、医疗、仿生和养殖等领域,并具有良好的经济效益和应用前景。 相似文献
15.
Jeena Jose Karippal H. N. Narasimha Murthy K. S. Rai M. Krishna M. Sreejith 《Polymer Bulletin》2010,65(8):849-861
This paper presents experimental results of the effect of amine functionalization of carbon nanofibers (CNF) on the electrical,
thermal, and mechanical properties of CNF/epoxy composites. The functionalized and non-functionalized CNFs (up to 3 wt%) were
dispersed into epoxy using twin screw extruder. The specimens were characterized for electrical resistivities, thermal conductivity
(K), UTS, and Vicker’s microhardness. The properties of the nanocomposites were compared with that of neat epoxy. The volume
conductivity of the specimens increased by E12 S/cm and E09 S/cm in f-CNF/epoxy and CNF/epoxy, respectively, at 3 wt% filler
loading. The increase in K for former was 106% at 150 °C, while for the latter it was only 64%. Similarly, UTS increased by 61% vs. 45% and hardness
65% vs. 43%. T
g increased with increase in filler content. SEM examinations showed that functionalization resulted in better dispersion of
the nanofibers and hence greater improvement in the studied properties of the nanocomposites. 相似文献
16.
Networks were prepared from Bisphenol A diglycidylether and 4,4′-diaminodiphenylmethane both in the presence of different amounts of imidazole and in the absence of any accelerator. The ratio of epoxy groups to amino hydrogen was varied: the networks were made with amino hydrogen excess, a stoichiometric ratio of epoxy groups to amino hydrogen, and an epoxy excess. The resulting networks were investigated by thermomechanical analysis, by torsion pendulum analysis and by uniaxial compression modulus measurements in the rubbery-plateau zone. Further characterization was done by sol gel analysis of the cured samples. It was shown that imidazole does not significantly influence the glass transition temperature and the soluble content of the samples of an excess of amino hydrogen was used. In the case of a stoichiometric ratio of epoxy groups to amino hydrogen and in the case of an epoxy excess, imidazole considerably influences the glass transition temperature of the networks. A dependence of the soluble content of the samples on imidazole concentration used for network synthesis was found mainly in epoxy excess systems. 相似文献
17.
Catherine A. Byrne Gary L. Hagnauer Nathan S. Schneider Robert W. Lenz 《Polymer Composites》1980,1(2):71-76
Monoepoxy phenyl glycidyl ether, curing agent p-chloroaniline, and the substituted urea type accelerator Monuron were used as a model system for studying the amine cure of epoxies. Reactions were carried out at 120°C with amine to epoxy equivalent rations of 0.25 and 1.0 Reaction mixtures were analyzed primarily by reverse phase high performance liquid chromatography. Three types of reactions occur; simple amine addition to epoxy, homopolymerization of epoxy, and epoxy polymerization involving the addition products. In the absence of accelerator the reaction involved simple addition. With the accelerator, there was competition between addition and polymerization, the balance depending on the amine to epoxy equivalent ratio. Both addition and polymerization were important for a ratio of 1, but polymerization far outweighed addition for a ratio of 0.25. 相似文献
18.
Catherine Jordan Jocelyne Galy Jean-Pierre Pascault Claude Mor Michel Delmotte Henri Jullien 《Polymer Engineering and Science》1995,35(3):233-239
An investigation was carried out into the effect ofa microwave cure on an epoxy prepolymer with a cycloaliphatic diamine mixture, as compared to a standard thermal cure. The microwave waveguide and process (propagation mode TE01) were adjusted to obtain large homogeneous samples. The extent of reaction, x, was measured during the microwave processing by size exclusion chromatography and differential scanning calorimetry. A good estimate of x was found using a modified DiBenedetto equation correlating x and the glass transition temperature Tg. The homogeneity of the samples was checked during the last steps of cure, showing the efficiency of the microwave processing and waveguide. The influence of the nature of the mold (metallic or dielectric) on the reaction kinetic was also investigated. Samples cured by both thermal and microwave processing were characterized by dynamic and static mechanical properties and then compared with those of fully crosslinked networks, i.e., postcured at a high temperature. 相似文献
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Several lamellar silicates (Montmorillonite, Hectorite, Mica) showing different host structures and aspect ratios were modified with octadecylammonium ions by a cationic exchange process. The resulting organoclays were characterized using thermal gravimetric analysis and X‐ray diffraction, which allowed us to estimate the amount of surfactants within the organoclays and their organization in the interlamellar spacing. Some local pseudo‐organizations were found and checked by differential scanning calorimetry (DSC). The interactions of organophilic silicates were evaluated, without any shear, with the precursors of a rubbery epoxy/amine network. These silicate/monomers interactions were monitored via the measurements of the interlamellar swelling, the surface energies and the physical gel formation. The organoclays used form gels in the monomers above the percolation threshold if no shear is applied and present a gel/sol transition at a critical shear stress. Gel strength determined from storage modulus and viscosity values determined at high shear rates reveal different organizations of clay in the monomers depending on the silicate aspect ratio and silicate/monomers interactions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1380–1390, 2006 相似文献