Tetraglycidyl Diaminodiphenyl Research Articles

Cure behavior and thermal stability of an epoxy: new bismaleimide blends for composite matrices

AbstractA new bismaleimide (BMI) resin was synthesized to formulate epoxy(tetraglycidyl diaminodiphenyl methane; TGDDM) – bismaleimide thermoset blends for composite matrix applications. 4,4′‐diaminodiphenyl methane (DDM) was used as an amine curing agent for the TGDDM. A Fourier transform infrared (FTIR) spectroscopy was employed to characterize the new BMI resin. Cure behavior of the epoxy–BMI blends was studied using a differential scanning calorimeter (DSC). DSC thermograms of the thermoset blends indicated two exothermic peaks. The glass transition temperature of the thermoset blends decreased with BMI content. Thermogravimetric analysis (TGA) was carried out to investigate thermal degradation behavior of the cured epoxy–BMI thermoset blends. The new BMI resin reacted partially with the DDM and weak intercrosslinking polymer networks were formed during cure of the thermoset blends.

The structural modification of epoxy resins by a liquid elastomer

A carboxy terminated poly-n-(butyl acrylate, acrylic acid, acrylonitryl) (PNBA) terpolymer was used as a modifier for three high-functionality epoxy resins, (i) epoxy novolac, (ii) triglycidyl-4-aminophenol (TGPAP) and (iii) tetraglycidyl diaminodiphenyl methane (TGDDM), used as matrix materials in polymer composites. The resin and elastomer were reacted using different amine catalysts at different temperatures. The progress of the reaction between the epoxy resin and elastomer was studied extensively by Fourier transform infrared (FMR) spectroscopy and differential scanning calorimetry (psc). The results show that hydroxy esterification and etherification occurred during the epoxy-carboxy group reaction. The possible reaction mechanism involved is discussed on the basis of the results obtained.

Effects of incorporating chromium acetylacetonate in epoxy matrix on the curing behavior and mechanical properties of Gr/Ep composites

Abstract The addition of chromium acetylacetonate in N, N, N’, N’, tetraglycidyl diaminodiphenyl methane/diaminodiphenyl sulfone/boron trifluoride‐monoethylene amine epoxy formulations for manufacturing unidirectional Gr/Ep laminates accelerated the curing reaction and increased the viscosity of resin during lamination. Differential scanning calorimetric and infrared spectroscopic results indicated that Cr(acac)3 acted like a cocatalyst with BF3MEA during curing. As the laminates were cured, the one incorporating 1 mol% Cr(acac)3 exhibited the highest GIC fracture toughness, flexural strength, and transverse tensile strength. The increased mechanical strength of the Gr/Ep laminates was due to the fact that the cohesive strength of the epoxy matrix was increased by the incorporated Cr(acac)3.

Water transport in graphite/epoxy composites

AbstractThe diffusive and mechanical behavior of tetraglycidyl diaminodiphenyl methane (TGDDM) resin‐based composites and diglycidyl ether of bisphenol‐A (DGEBA) resin‐based graphite/epoxy composites were investigated during water sorption at different temperatures. The water‐absorption kinetics in both systems at 50, 70, 90, and 100°C were fitted by a Fickian diffusion model. However, a Langmuir‐type, two‐step sorption behavior was observed for water transport in DGEBA‐based systems at 50 and 70°C. Using scanning electron microscopy, internal cracks due to water absorption were found in the DGEBA‐based samples after conditioning at 90 and 100°C in water, whereas no cracks were detected in TGDDM‐based samples conditioned in water at 100°C. Ultrasonic testing did not show significant modulus or density change of the TGDDM‐based samples conditioned in water at 100°C. No significant changes of dynamic modulus or damping factor were observed for the TGDDM‐based samples redried after immersion in 100°C water, whereas slight changes were observed above 120°C for the samples containing absorbed water. However, both water‐containing and redried DGEBA‐based samples showed a decrease of dynamic modulus and an ω‐transition around 120°C. A single‐fiber fragment test revealed that the absorbed water at 80°C reduced significantly the interfacial shear strength of DGEBA/DDA resin‐AS4 fiber samples and DGEBA/DDA resin‐AU4 fiber samples. © 1993 John Wiley & Sons, Inc.

Comparative studies on the curing kinetics and thermal stability of tetrafunctional epoxy resins using various amines as curing agents

The curing reactions of the epoxy resins tetraglycidyl diaminodiphenyl methane (TGDDM) and tetraglycidyl methylenebis (o-toluidine) (TGMBT) using diaminodiphenyl sulfone (DDS), diaminodiphenyl methane (DDM) and diethylenetriamine (DETA) as curing agents were studied kinetically by differential scanning calorimetry. The dynamic scans in the temperature range 20°–300°C were analyzed to estimate the activation energy and the order of reaction for the curing process using some empirical relations. The activation energy for the various epoxy systems is observed in the range 71.9–110.2 kJ·mol−1. The cured epoxy resins were studied for kinetics of thermal degradation by thermogravimetry in a static air atmosphere at a heating rate of 10 deg·min−1. The thermal degradation reactions were found to proceed in a single step having an activation energy in the range 27.6–51.4 kJ·mol−1.

Thermal oxidative degradation of an epoxy resin

This study of the thermodegradation of the tetraglycidyl diamino diphenyl methane/diaminodiphenylsulfone system (TGDDM/DDS) defines the differents steps of the carbonization process. It characterizes, in particular, the domain of existence of an expanded carbonaceous structure which is constituted of small domains of turbostratic carbon. Moreover, this present work discusses the role of oxygen in the formation of this structure and shows that there is competition between the carbonization process and the oxidative degradation.

Physical and mechanical behavior of tetraglycidyl diaminodiphenyl methane (TGDDM)/m‐phenylene diamine (m‐PDA) epoxy systems

AbstractThe rheological behavior of a tetraglycidyl diaminodiphenyl methane with a tetrafunctional aromatic diamine has been studied in terms of the influence of curing agent content and temperature. In this work, critical times corresponding to gelation are used as a measure of activation energy. The dynamic mechanical behavior has been used to analyze the curing extent of these epoxy systems with different amine contents before and after thermal posttreatment. The β‐relaxation peak temperature is found to increase with the curing agent content and also after thermal posttreatment. This has been related to the rise of crosslinking extent. Dependence of flexural mechanical properties on curing agent content and the postcure process has also been determined.

Kinetic model for the curing reaction of a tetraglycidyl diamino diphenyl methane/diamino diphenyl sulfone (TGDDM/DDS) epoxy resin system

AbstractA kinetic model based on reaction mechanisms was proposed for the description of the curing behavior of a TGDDM/DDS resin system. The characteristic of this model is the separation of the non‐autocatalytic part from the autocatalytic part of the reaction, so the model can match the well‐established pseudo second order reaction mechanism, as proposed by many other studies about the epoxide/amine reaction. The present model was compared with two other widely used models for the autocatalytic curing behavior of epoxide/amine system, i.e., an equation based on a single rate constant and another based on pure phenomenological analysis, by using DSC data. It was found that the reaction rate calculated from this new model can fit the DSC empirical result much better than those calculated from the other two models. Parallel studies on some other resins, such as the DGEBA/m‐PDA system, also proved the superiority of this kinetic model. Results have revealed that the new model was valid for most of the epoxide/1o‐amine systems studied. A discrepancy did appear as the epoxide/amine molar ratio and/or the isothermal curing temperature reached certain limits, owing to the occurrence of side reactions.

Thermal analysis of standard and toughened high-performance epoxy matrices

The reaction kinetics of commercial high-performance matrices has been characterized by differential scanning calorimetry (DSC). Standard and new toughened epoxy matrix prepregs based on tetraglycidyl diamino diphenyl methane-diamino diphenyl sulfone (TGDDM-DDS) formulations have been studied. The toughened epoxy matrix prepreg, modified by addition of a second thermoplastic phase, is characterized by a lower reactivity, probably affected by the presence of the second non-reactive thermoplastic phase. The effect of diffusion control phenomena on the reaction kinetics, associated with evolution of the glass transition temperature as a function of the degree of polymerization and crosslinking, has been considered in the formulation of a modified nth-order kinetic model. This describes incomplete reactions in isothermal tests and the heating rate dependence of dynamic test results, and can thus be used to describe the behaviour of the reactive matrix during processing under complex thermal conditions.

Isothermal and dynamic reaction kinetics of high performance epoxy matrices

AbstractThe reaction kinetics of the epoxy matrix of a commercial prepreg for high performance composites, based on tetraglycidyl diamino diphenyl methanediamino diphenyl sulfone (TGDDM‐DDS) formulation, has been characterized by differential scanning calorimetry (DSC). A phenomenological kinetic model, able to describe the behavior of the system during normal processing operations has been formulated. The diffusion control phenomena, related to the evolution of the glass transition temperature as a function of the degree of polymerization, has been considered in the formulation of the kinetic model. Isothermal and dynamic tests have been used to calculate the model parameters and to verify the proposed model. The model is able to describe incomplete reactions in isothermal tests and heating rate dependence of dynamic test thermograms, and it has been also successfully applied to DSC experiments performed with complex thermal conditions commonly used in the processing of high performance composites.

Properties of Glass-fibre-reinforced Composites of Epoxy Resins Cured with Different Amines

Glass-fibre-reinforced epoxy composites were fabricated from the matrix resins diglycidyl ether of bisphenol A (DGEBA) and tetraglycidyl diaminodiphenyl methane (TGDDM) using different amines as curing agents. The characteriation of these epoxy laminates included resistance to chemical reagents, mechanical properties [e.g. shore-D hardness, flexural strength and interlaminar shear strength (ILSS)] as well as dielectric properties including dielectric constant, loss tangent (tan δ), electrical resistance and breakdown voltage.

Differential scanning calorimetry cure studies on the effect of addition of epoxy diluents of tetrafunctional epoxy resins

AbstractThe effect of the addition of p‐aminophenol and aniline‐based epoxy diluents on the curing behavior of highly viscous tetraglycidyl diamino diphenyl methane resin with diamino diphenyl sulfone hardener have been investigated kinetically by differential scanning calorimetry. Dynamic scans were carried out over a temperature range 30–300°C for different resin formulations. Isothermal scans at four differnt temperatures have also been carried out for the evaluation of kinetic parameters. Heat flow measurements at different heating rates have indicated the evidence of autocatalytic behavior of curing reaction following a simple nth‐order kinetics.

Effects of ionizing radiation on epoxy, graphite fiber, and epoxy/graphite fiber composites. Part II: Radical types and radical decay behavior

AbstractElectron spin resonance (ESR) investigations of line shapes and radical decay behavior have been made on an epoxy based on tetraglycidyl diaminodiphenyl methane (TGDDM)/diaminodiphenyl sulfone (DDS), T‐300 graphite fiber, and T‐300/5208 (graphite fiber/epoxy) composites after irradiation with Co60 γ‐radiation or 0.5 MeV electrons. Two kinetically distinct radical species are found in the irradiated epoxy as the temperature is raised beyond 120 K following irradiation of samples at 77 K with Co60 γ. One has been termed a fast‐decaying species and the other a slow‐decaying species. The ratio of fast‐decaying/slow‐decaying radicals increases as the decay temperature rises. The fast‐decaying radicals at room temperature are attributed largely to alkyl type radicals residing in regions of relatively low crosslink density, while the long‐lived radicals are attributed to radicals residing in the highly crosslinked regions of the epoxy. A large concentration (ca. 1020 to 1021 spins/g) of unpaired electrons was found in unirradiated graphite fiber which masked the ESR spectral change in irradiated composites.

Effects of ionizing radiation on epoxy, graphite fiber and epoxy/graphite fiber composites. Part I: Surface energy changes

AbstractSurface energy changes of an epoxy based on tetraglycidyl diaminodiphenyl methane (TGDDM)/diaminodiphenyl sulfone (DDS), T‐300 graphite fiber, and T‐300/5208 (graphite fiber/epoxy) composites have been investigated after irradiation with 0.5 MeV electrons. The surface energy of TGDDM‐DDS epoxy increases monotonically with radiation doses up to 1,000 Mrad mainly due to increased concentration of polar groups. IR and ESCA spectral evidence indicates that carbonyl groups are formed, probably from the tertiary hydrogen at the carbon where the OH group is attached in the cured epoxy. The polarity of the graphite fiber and the graphite fiber/epoxy interface also increases with radiation dose. These results and the roles of oxygen are discussed in connection with mechanical properties of epoxy/graphite fiber composites exposed to ionizing radiation.

Inverse gas chromatography used to follow kinetics of epoxy-amine reactions in the molten state

Polycondensation kinetics of epoxy-amine model systems were investigated with inverse gas chromatography. The results obtained were applied to the study of cross-linking kinetics of two epoxy prepolymers, tetraglycidyl diamino diphenyl methane and diglycidyl ether of bisphenol A, with diamino diphenyl sulphone. Data furnished by inverse gas chromatography showed zones of gelation and of vitrification. Based on kinetics established by isothermal microcalorimetry, it was possible to determine reaction advancement in these transition zones. The results show that advancement of both reaction systems to the transition points T 1 and T 2 is very sensitive to curing temperature and to the stoichiometry of the mixture. Finally, the vitreous transition temperatures of the cross-linked systems were determined and compared to those determined with differential scanning calorimetry.

Network structure and plasticization of epoxy‐based resins

AbstractThe sorption behaviour of water molecules in epoxy‐based thermosetting networks is discussed and related to the modifications of their properties. The hypothesized sorption modes and the corresponding mechanisms of plasticization are discussed on the basis of experimental vapor and liquid sorption tests, differential scanning calorimetry (DSC), thermomechanical analysis (TMA) studies, and dynamic mechanical analyses.Three modes of moisture sorption are assumed: increase in the free volume of the system, hydrogen bonding onto hydrophilic groups present in the network and adsorption onto the surfaces of “holes” which define the excess free volume of the glassy structure. The less stiff Diglycidyl ether of bisphenol‐A (DGEBA) systems have no appreciable sorption via hydrogen bonding, but rather most of the moisture absorbed is due to the free volume increase and adsorption in the “holes”. On the other hand, the stiffer Tetraglycidyl Diaminodiphenyl Methane (TGDDM) systems absorb more moisture through significant hydrogen bonding rather than by the free volume increase. High plasticizations, evident as Tg depressions by 30 to 80°C, are possible being experimentally observed for the stiffer TGDDM resins.Relationships derived from the free volume theory or the classical thermodynamic treatment may be used to describe the dependence of Tg on the composition of miscible blends.

Effect of processing variables on the durability of epoxy resins for composite systems

The Flory approach has been used to described the molecular characteristics of the non-linear polymerization of tetraglycidyl diamino diphenyl methane (TGDDM) cured with diphenyl sulfone (DDS). The cure behavior of commercial grade TGDDM-DDS mixtures was analyzed by means of differential scanning calorimetry (DSC), high-pressure liquid chromatography (HPLC), and steady and dynamic viscosity measurements. The gelation limits and molecular distribution measured in isothermal tests were in good agreement with experimental determinations. The gelation theory was further combined with the WLF treatment of the temperature dependency of the viscoelastic behavior for the reacting system in order to describe the viscosity profiles during complex cure cycles. Furthermore, this work relates moisture sorption and plasticization of two epoxy systems to hydrothermal and processing variables. A low cross-linked diglycidyl ether of bisphenol-A (DGEBA) cured with linear amines, such as ethylene diamine (EDA), diethylene triamine (DETA) and triethylene tetramine (TETA), and the highly cross-linked TGDDM-DDS system, have been studied. An increase in the equilibrium moisture content was observed as a result of thermal cycling in liquid environments. The hydrothermal interactions are shown to produce changes in the epoxy network structures and in the moisture sorption behavior.

Low‐temperature thermal decomposition of an epoxy resin

AbstractThe thermal decomposition of the epoxy resin system, MY720 (70 wt % tetraglycidyl diaminodiphenyl methane), cured with Eporal (diamino diphenyl sulfone), was investigated at 125–215°C. The primary decomposition product was propenal. Several other aldehydes were observed; however, they are formed during cure and are not thermal decomposition products. The apparent activation energy for the production of propenal was 67 kJ/mol (16 kcal/mol). Possible mechanisms for the source of this compound are discussed.

Thermokinetics and chemorheology of the cure reactions of the tetraglycidyl diamino diphenyl methane–diamino diphenyl sulfone epoxy systems

AbstractThe cure behavior of commercial grade TGDDM–DDS mixtures of compositions ranging from 10 to 100 phr of hardener and the thermal polymerization of the epoxy component are analyzed by means of differential scanning calorimetry. The kinetic parameters and heats of reaction determined in isothermal and dynamic scans suggest that DDS primary amine addition and epoxide etherification dominate the cure reactions. The primary amine epoxide addition is characterized by overall heat of reaction (referred to the weight of the epoxy component) of 255 cal/g and by an activation energy of 16.6 kcal/mol. The corresponding values for the etherification reaction are, respectively, 170 cal/g and 41 kcal/mol. A method of derivation of the epoxide conversion from the heat evolved in DSC thermal scans of these systems is presented. The results are in good agreement with independent IR determinations. The steady shear and oscillatory viscosity measurements and the calorimetric analysis of the isothermal cure at 140°C, 160°C, and 180°C of a TGDDM–DDS mixture containing 35 phr of hardener indicate that gelation is principally governed by the primary amine addition. The gelation limits calculated in isothermal tests by combining the calorimetric analysis and the theory describing the nonlinear copolymerization of the tetrafunctional TGDDM with an essentially difunctional DDS were in good agreement with the values experimentally determined through rheological measurements.

The mechanism of cure of tetraglycidyl diaminodiphenyl methane with diaminodiphenyl sulfone

Journal of Applied Polymer ScienceVolume 28, Issue 6 p. 2131-2131 ErratumFree Access The mechanism of cure of tetraglycidyl diaminodiphenyl methane with diaminodiphenyl sulfone A. Gupta, A. Gupta Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorM. Cizmecioglu, M. Cizmecioglu Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorD. Coulter, D. Coulter Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorR. H. Liang, R. H. Liang Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorA. Yavrouian, A. Yavrouian Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorF. D. Tsay, F. D. Tsay Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorJ. Moacanin, J. Moacanin Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this author A. Gupta, A. Gupta Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorM. Cizmecioglu, M. Cizmecioglu Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorD. Coulter, D. Coulter Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorR. H. Liang, R. H. Liang Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorA. Yavrouian, A. Yavrouian Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorF. D. Tsay, F. D. Tsay Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this authorJ. Moacanin, J. Moacanin Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109Search for more papers by this author First published: June 1983 https://doi.org/10.1002/app.1983.070280625AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume28, Issue6June 1983Pages 2131-2131 RelatedInformation