Tetraglycidyl Diaminodiphenyl Methane Research Articles

Morphology, thermal relaxations and mechanical properties of layered silicate nanocomposites based upon high-functionality epoxy resins

This paper investigates the possibility of improving the mechanical properties of high-functionality epoxy resins through dispersion of octadecyl ammonium ion-modified layered silicates within the polymer matrix. The different resins used are bifunctional diglycidyl ether of bisphenol-A (DGEBA), trifunctional triglycidyl p-amino phenol (TGAP) and tetrafunctional tetraglycidyldiamino diphenylmethane (TGDDM). All resins are cured with diethyltoluene diamine (DETDA). The morphology of the final, cured material was probed by wide-angle X-ray scattering, as well as optical and atomic force microscopy. The α- and β-relaxation temperatures of the cured systems were determined using dynamic mechanical thermal analysis. It was found that the presence of organoclay steadily decreased both transition temperatures with increasing filler concentration. Further, the effect of different concentrations of the alkyl ammonium-modified layered silicate on the toughness and stiffness of the different epoxy resins was analyzed. All resin systems have shown improvement in both toughness and stiffness of the materials through the incorporation of layered silicates, despite the fact that it is often found that these two properties cannot be simultaneously achieved.

Isothermal curing by dynamic mechanical analysis of three epoxy resin systems: Gelation and vitrification

AbstractTimes to gelation (tgel) and times to vitrification (tvit) during isothermal curing for the epoxy systems diglycidyl ether of bisphenol A (DGEBA)/1,3‐bisaminomethylcyclohexane (1,3‐BAC), tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM)/4‐4′‐diaminodiphenylsulfone (DDS), and TGDDM/epoxy novolac (EPN)/DDS were measured at different curing temperatures. This article reports on a method to determine tgel and tvit by dynamic mechanical analysis (DMA). Gelation was determined at the onset of the storage modulus or by the peak of the loss factor. Vitrification was defined as the curve of the storage modulus as the curve reached a constant level (endset) in DMA tests. The experimental values obtained for tgel and tvit were compared with values obtained by other experimental methods and with theoretical values (tgel's) or indirect determinations (tvit's). From kinetic analysis by differential scanning calorimetry, conversions corresponding to gelation were obtained for the three systems; this yielded a constant value for each system that was higher than theoretical value. Values of the apparent activation energies of the DGEBA/1,3‐BAC, TGDDM/DDS, and TGDDM/EPN/DDS epoxy systems were obtained from plots of tgel's against reciprocal temperatures. They were 53.2, 58.2, and 46.5 kJ/mol, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 78–85, 2002

Rheokinetic variations during curing of a tetrafunctional epoxy resin modified with two thermoplastics

The curing kinetics of an epoxy matrix based on tetraglycidyl diamino diphenyl methane polymerized with diamino diphenyl methane and those for its mixtures with poly(methyl methacrylate) and poly(ethersulfone) (PES) at compositions ranging from 0 to 15 wt.% were studied using differential scanning calorimetry in isothermal and dynamical conditions. Rheological properties were also measured to follow curing evolution. Apparent activation energies were calculated from the so obtained gelation times. Thermoplastic addition to the thermosetting resin delayed the polymerization, and above all in the PES case but it does not modify the cure kinetics of the thermosetting matrix. A modified autocatalytic kinetic model which contains the diffusional term was used. Satisfactory results were obtained as conversion curves fitted quite well the experimental data.

A systematic study of the microwave and thermal cure kinetics of the TGDDM/DDS and TGDDM/DDM epoxy‐amine resin systems†

AbstractThe microwave and thermal cure processes for the epoxy‐amine systems N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenyl methane (TGDDM) with diaminodiphenyl sulfone (DDS) and diaminodiphenyl methane (DDM) have been investigated. The DDS system was studied at a single cure temperature of 433 K and a single stoichiometry of 27 wt% and the DDM system was studied at two stoichiometries, 19 and 32 wt%, and a range of temperatures between 373 and 413 K. The best values of the kinetic rate parameters for the consumption of amines have been determined by a least squares curve fit to a model for epoxy‐amine cure. The activation energies for the rate parameters for the MY721/DDM system were determined as was the overall activation energy for the cure reaction which was found to be 62 kJ mol−1. No evidence was found for any specific effect of the microwave radiation on the rate parameters, and the systems were both found to be characterized by a negative substitution effect. Copyright © 2001 John Wiley & Sons, Ltd.

Effect of water sorption on the structure and mechanical properties of an epoxy resin system

The characteristics of sorption and diffusion of water in an amine-cured epoxy system based on tetraglycidyl diaminodiphenylmethane and a novolac glycidyl ether resin were studied as a function both of the polymer microstructure, known from previous works, and the temperature. Water-sorption experiments and dynamic mechanical analysis (DMA) were performed. Tensile stress–strain and Rockwell hardness tests were conducted to investigate the effects of absorbed water on the mechanical properties of the material. Competing effects of the sorption of water in the free volume and of strong interactions between water molecules and polar groups of the network were used to explain the diffusional behavior observed, which followed Fick's second law. DMA analysis seemed to be sensitive to the water effects and the viscoelastic behavior was related both to the water-sorption processes and to the microstructure of the system. An important impact of water uptake on the tensile properties at break was also appreciated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 71–80, 2001

Morphologies and mechanical properties of polyarylate/liquid crystalline polymer blends compatibilized by a multifunctional epoxy resin

The tetrafunctional epoxy resin, tetraglycidyl-4′,4′-diaminodiphenyl methane (TGDDM), has been investigated as an efficient reactive compatibilizer for the blends of polyarylate (PAr) with a liquid crystalline polymer (LCP). TGDDM can react with PAr and LCP at the interface simultaneously to produce the PAr-co-TGDDM-co-LCP mixed copolymers during melt blending. These copolymers tend to anchor along the interface as the result of the interfacial reaction and thus serve as effective compatibilizers to reduce the interfacial tension and to enhance the interfacial adhesion in the solid state. The morphologies of the PAr/LCP blends were inspected by means of scanning electron microscopy (SEM). It is observed that the dispersed LCP phase domains reduce obviously after compatibilization. Furthermore, it is also found that the reduced interfacial tension caused by the addition of TGDDM plays a vital role in affecting the deformation of the LCP phase domains in the compatibilized PAr/LCP blends. The LCP phase tends to deform into greater numbers and finer fibrils with high aspect ratio after the addition of TGDDM in those blends containing adequate LCP content (> 10 %). In the blend containing low amount of LCP (Par / LCP = 95/5) with high TGDDM content (0.3 phr or higher), however, the LCP phase can only exist as fine but short fibrils or even ellipsoids. The overall mechanical properties of the PAr/LCP blends are substantially improved after compatibilization by this coupling-type reactive compatibilizer. The generation of LCP fibrils with high aspect ratio and improved interfacial adhesion are the two hinges to enhance the performance of the compatibilized PAr/LCP blends.

Effect of poly(styrene-co-acrylonitrile) on the curing of an epoxy/amine resin

The cure kinetics and the miscibility have been studied in blends of poly(styrene-co-acrylonitrile) (SAN) with tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) and 4-4′-diaminodiphenylsulphone (DDS) as hardener. Differential scanning calorimetry (DSC) was the technique used for dynamic and isothermal experiments. Binary mixtures of SAN with the epoxy resin show complete miscibility over the whole composition range, displaying a single glass transition temperature. Kinetic analysis were performed using three kinetic models: Kissinger, Flynn–Wall–Ozawa and the phenomenological model developed by Kamal. Activation energies and kinetic parameters were determined by fitting experimental data. Diffusion control is incorporated to describe the cure in the latter stages, predicting the cure kinetics over the whole range of conversion. The autocatalytic mechanism was observed for the neat system and the epoxy-SAN blends. The reaction rates for the epoxy blends were found to be lower than of the neat epoxy. The reaction rates and the maximum conversions decreased when SAN contents increase, due to reduction of mobility of the reacting species.

The cure behavior of tetraglycidyl diaminodiphenyl methane with diaminodiphenyl sulfone

It is well known that the preparation of an high-performance composite product depends not only on raw materials (resin and fiber) but also on the curing technological condition, or rather, the determination of the curing technological parameters. In this study torsional braid analysis (TBA) is used to study the cure behavior of tetraglycidyl diaminodiphenyl methane (TGDDM or Ag-80) with diaminodiphenyl sulfone (DDS), providing theoretical data for determining the curing condition of this resin matrix composites. Isothermal TBA technique is used to obtain a time–temperature-transformation (TTT) cure diagram, according to which the three different types of cure behavior are discussed. The data for T g for different cure temperatures and times provide and estimation of the time to full cure vs. isothermal cure temperature for the resin system. An empirical T g– T c–time (TTT) equation is also developed.

Reactive processing of poly(ethylene terephthalate) modified with multifunctional epoxy-based additives

The use of multifunctional epoxy-based modifiers to increase the melt strength of poly(ethylene terephthalate) (PET) has been investigated, with the aim of producing PET foams by an extrusion process. The reaction conversion has been studied as a function of time by the measurement of torque in an internal mixer. A tetraglycidyl diamino diphenyl methane (TGDDM) resin was selected for the investigation of the modifier concentration effect on the reaction conversion. Using a stoichiometric concentration of TGDDM, the molecular weight distribution of modified PET, as determined by gel permeation chromatography (GPC), showed an eight-fold increase of the z-average molecular weight ( M z ) and the presence of branched molecules of very large mass. The resulting intrinsic viscosity of the modified PET was 1.13 dl/g.

The Curing Process and Moisture Transport in a Tetrafunctional Epoxy Resin as Investigated by FT-NIR Spectroscopy

An epoxy resin formulation composed of tetraglycidyl-4, 4′ diaminodiphenylmethane (TGDDM) and 4, 4′ diaminodiphenylsulfone (DDS) was investigated by Fourier transform near-infrared (FT-NIR) spectroscopy. In situ isothermal measurements allowed us to obtain the concentration versus time curves of the various reactive groups present in the system, thus affording a complete characterization of the curing process. The same experimental approach was used to monitor the transport of moisture into the resin at several temperatures. The data gathered in this way revealed a good agreement with conventional gravimetric measurements, which verifies the reliability and accuracy of FT-NIR spectroscopy for the study of these transport processes.

Miscibility and mechanical properties of tetrafunctional epoxy resin/phenolphthalein poly(ether ether ketone) blends

Phenolphthalein poly(ether ether ketone) (PEK-C) was found to be miscible with uncured tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM), which is a type of tetrafunctional epoxy resin (ER), as shown by the existence of a single glass transition temperature (Tg) within the whole composition range. The miscibility between PEK-C and TGDDM is considered to be due mainly to entropy contribution. Furthermore, blends of PEK-C and TGDDM cured with 4,4′-diaminodiphenylmethane (DDM) were studied using dynamic mechanical analysis (DMA), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). DMA studies show that the DDM-cured TGDDM/PEK-C blends have only one Tg. SEM observation also confirmed that the blends were homogeneous. FTIR studies showed that the curing reaction is incomplete due to the high viscosity of PEK-C. As the PEK-C content increased, the tensile properties of the blends decreased slightly and the fracture toughness factor also showed a slight decreasing tendency, presumably due to the reduced crosslink density of the epoxy network. SEM observation of the fracture surfaces of fracture toughness test specimens showed the brittle nature of the fracture for the pure ER and its blends with PEK-C. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 598–607, 2001

The transport of water in a tetrafunctional epoxy resin by near-infrared Fourier transform spectroscopy

An epoxy resin formulation composed of tetraglycidyl-4,4′-diamino diphenylmethane (TGDDM) and 4,4′diamino diphenyl sulfone (DDS) was investigated by Fourier transform near infrared (FT-NIR) spectroscopy and dynamic-mechanical analysis. Both techniques have demonstrated the essentially complete cure state of the resin with the adopted curing schedule. A novel feature of this work is the possibility of monitoring the transport of water into the resin by using of an FT-NIR spectrometer as a detector in place of the currently employed gravimetric detectors. The data gathered at different temperatures have revealed a good agreement with conventional gravimetric measurements, which verifies the reliability and accuracy of the experimental approach presented herein.

Cure kinetics of multifunctional epoxies with 2,2?-dichloro-4,4?-diaminodiphenylmethane as hardener

The curing behavior of the epoxy resin N,N,N′,N′-tetraglycidyldiaminodiphenyl methane (TGDDM) with triglycidyl p-aminophenol as a reactive diluent was investigated using 2,2′-dichloro-4,4′-diaminodiphenylmethane (DCDDM) as the curing agent. The effect of the curing agent on the kinetics of curing, shelf-life, and thermal stability in comparison with a TGDDM-diaminodiphenylsulfone (DDS) system was studied. The results showed a lesser activation energy at the lower level of conversion with a broader cure exotherm for the epoxy-DCDDM system in comparison with the epoxy-DDS system, although the overall activation energy for the two systems was comparable. TGA studies showed more stability in the epoxy-DCDDM system than in the epoxy-DDS system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2097–2103, 2000

Physical Aging of a Tetrafunctional/phenol Novolac Epoxy Mixture Cured with Diamine. DSC and DMA measurements

The physical aging of a system containing tetraglycidyl-4-4′-diaminodiphenylmethane (TGDDM), with a multifunctional novolac glycidyl ether resin hardened by 4,4′-diaminodiphenylsulphone (DDS) has been investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Samples fully cured were aged at temperatures between 200 and 250°C, during periods of time from 1 to a maximum of 336 h. Furthermore, the dynamic mechanical relaxation behaviour annealed at temperature of 220°C, was studied, aging during 24 and 168 h. The effect of the enthalpy relaxation during DSC heating scan is shown by the presence of an endothermic peak whose position and intensity depends on the aging conditions, both temperature and time. DSC studies suggest that enthalpy relaxation increases gradually with aging time to a limiting value for each temperature where structural equilibrium is reached. DMA results show that the effect of aging is to cause chain stiffening and a decrease in the height of the peak value of the loss factor.

複合材料 リサイクルを目的としたアミン硬化エポキシ樹脂の硝酸による分解

Three kinds of epoxy resins were decomposed by nitric acid in order to establish a recycling method of epoxy resin. Specimens were immersed in 80°C nitric acid (4M and 6M) and decomposed products were recovered. The molecular weight distributions and chemical structures of the products were analyzed by using Size Eliminated Chromatograph and FT-IR, respectively. For the case of bisphenol A type epoxy resin cured with amine, a derivative of monomer was formed due to the decomposition at C-N bonds. The derivative of monomer was dissolved in nitric acid and was extracted with ethyl acetate. 2, 4, 6-trinitrophenol, which was produced by the breakage of main chain and subsequent nitration, was also recovered. Nitric acid attacked the C-N bonds in bisphenol F type epoxy resin cured with amine more selectively because of the existence of methylene group in the main chain. The yield of recovered decomposed product which contained derivative of the monomer of bisphenol F type epoxy resin was more than the case of bisphenol A. With regard to tetraglycidyl diamino diphenyl methane (TGDDM) resin cured with diamino diphenyl methane (DDM), the chemical structure of cured resin is symmetric and repetitive. Hence, decomposed product of TGDDM/DDM was recovered as a nearly single compound of 2, 4, 6-trinitroaniline.

Low moisture absorptive epoxy formulations for Gr/Ep laminates

AbstractThe incorporation of 2‐undecyl‐imidazole (C11Z) and chromium acetylacetonate (Cr(acac)3) additives into N, N, N′, N′‐tetraglycidyl diaminodiphenylmethane (TGDDM)/diaminodiphenylsulfone (DDS) epoxy formulations was found to significantly decrease the moisture absorption of their prepared graphite/epoxy laminates. However, the same additions did not much affect the moisture absorption of the cured TGDDM/DDS neat resins. Thus, the former case was attributed to the processing effects in view of the fact that C11Z pre‐reacting with TGDDM during lay‐up process produced the ether‐linkage polymer chains in the epoxy networks and raised the viscosity. The following compacting stage of laminates was believed to squeeze the small molecules such as unreacted TGDDM, DDS and Cr(acac)3, toward the surface of carbon fibers and increase the chance of Cr(acac)3 to block the hydroxyl groups in the epoxy networks produced by the reactions between TGDDM and DDS. Some evidence was provided to support the above hypothesis in this study.

Influence of processing method on the fracture toughness of thermoplastic-modified, carbon-fiber-reinforced epoxy composites

The influence of processing method on the fracture toughness of thermoplastic-modified, carbon-fiber-reinforced epoxy composites has been investigated. The composites used in this work were prepared from toughened epoxy (176°C cure) prepregs with carbon fiber reinforcement. Tetraglycidyl-4,4 ′-diaminodiphenyl methane (TGDDM) type epoxy resin was used as a matrix material and the polyacrylonitrile based T-300 (12 K) type was used as a carbon fiber. The prepregs had 37 wt.% of resin and a fiber areal weight of 145 ± 3 g/m 2. Poly(butylene terephthalate) (PBT) was used as a dispersed phase. Nylon 6 was also tried as a dispersed phase. In order to optimize the preparation and the toughness of the prepreg, three different processes were attempted; spray-up, double pass, and general types. The mode-II interlaminar fracture toughness was determined in terms of G IIc by using the end-notch-flexure (ENF) test. The toughness of the composite was investigated as a function of the prepreg preparation method, resin formulation, and the kinds and contents of a dispersed phase. It was found that the double-pass impregnation produces composites with higher toughness, compared with the general type of preparation process. Prepregs with an epoxy formulation with lower TGDDM content exhibited higher toughness. The prepregs toughened with Nylon 6 always showed higher G IIC, glass-transition temperatures, as compared with those with PBT, regardless of the preparation methods and the formulation. Finally, it was concluded that the toughness of composites made from prepreg prepared by the spray-up preparation method shows a maximum when the PBT content was 15 phr.

Cure Kinetics of Amine Cured Tetrafunctional Epoxy Blends with Poly(Styrene-Co-Acrylonitrile)

Cure kinetics using a differential scanning calorimetry (DSC) technique were analyzed for a thermoplastic modified tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) epoxy resin cured with diaminodiphenylsulphone (DDS), an aromatic diamine. The neat resin and its blends with the poly(styrene-co-acrylonitrile) (SAN) of various compositions were studied by applying a phenomenological model proposed by Kamal. Kinetic parameters were determined by fitting experimental data. This model gives a good description of cure kinetics up to the onset of vitrification. Diffusion control was incorporated to describe the cure in the latter stages of cure. The results showed that the addition of SAN did not alter the nature of the reaction, but the reaction rates and final conversions decreased when SAN contents increase, due to reduction of mobility of the reacting species.

Thermal Degradation of Tetrafunctional/Phenol Novalac Epoxy Mixture Cured with a Diamine

The effect of thermal degradation on the mechanical behaviour of a system containing both tetraglycidyl-4-4′-diaminodiphenylmethane (TGDDM) and a multifunctional novolac glycidyl ether (EPN) resins, cured with 4,4′-diaminodiphenylsulphone (DDS) has been studied using dynamic mechanical analysis (DMA) and tensile tests. Different curing paths using the isothermal time-temperature-transformation (TTT) diagram for this system were designed, obtaining thermosetting materials with different conversions. The influences of the degree of cure and of the aging temperature were also studied. The results showed different trends in the dynamic mechanical properties and an increase in the stiffness of the material with increasing aging time. Changes were faster and more intense with the higher temperature.

Polymer blends of polyamide-6 (PA6) and poly (phenylene ether) (PPE) compatibilized by a multifunctional epoxy coupler

A tetrafunctional epoxy monomer, N,N,N*-N*-tetraglycidyl-4,4*-diaminodi- phenyl methane (TGDDM), has demonstrated to be a highly efficient reactive compati- bilizer in compatibilizing the immiscible and incompatible polymer blends of polyamide- 6 (PA6) and poly(2,6-dimethyl-1,4-phenylene ether) (PPE). This epoxy coupler can react with both PA6 and PPE to form various PA6-co-TGDDM-co-PPE mixed copoly- mers. These interfacially formed PA6-co-TGDDM-co-PPE copolymers tend to anchor along the interface to reduce the interfacial tension and result in finer phase domains and enhanced interfacial adhesion. A simple one-step melt blending has demonstrated to be more efficient in producing a better compatibilized PA6/PPE blend than a two- step sequential blending. The mechanical property improvement of the compatibilized blend over the uncompatibilized counterpart is very drastic, by considering the addition of a very small amount, a few fractions of 1%, of this epoxy coupling agent. q 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1805-1819, 1998