Tetraglycidyl Diaminodiphenyl Methane Research Articles

Cure kinetics and mechanical properties of the blend system of epoxy/diaminodiphenyl sulfone and amine terminated polyetherimide-carboxyl terminated poly(butadiene-co-acrylonitrile) block copolymer

The cure kinetics of blends of epoxy resin (4,4’-tetraglycidyl diaminodiphenyl methane; TGDDM)/curing agent (diaminodiphenyl sulfone; DDS) with ATPEI (amine terminated poly-etherimide) -CTBN (carboxyl terminated poly (butadiene-co-acrylonitrile)) block copolymer (AB type) were studied using differential scanning calorimetry under isothermal conditions to determine the reaction kinetic parameters such as activation energy and reaction constants. Final cure conversion decreased with increasing amount of AB in the blends. A diffusion controlled reaction was observed as the cure conversion increased, and the curing reaction was successfully analyzed by incorporating the diffusion control term in the rate equation for the epoxy/DDS/AB blends. The fracture toughness was improved to about 350% compared to that of the unmodified resin at 30% of AB block copolymer. This is attributed to the formation of co-continuous morphology between the epoxy phase and AB block copolymer phase. By increasing the amount of AB, the modulus of the cured blends decreased, which was due to the presence of CTBN rubbery phases.

Fracture toughness and water uptake of high-performance epoxy/nanoclay nanocomposites

Aircraft grade epoxy–clay nanocomposites based on tetraglycidyl-4, 4′-diaminodiphenylmethane (TGDDM) cured with diaminodiphenyl sulphone (DDS) were synthesized. Nanoclay was dispersed in both acetone and an acetone epoxy solution with a high pressure mixing (HPM) method to form pastes. The basal spacing of the nanoclay in these pastes was increased as observed from X-ray diffraction (XRD) data. Transmission electron microscopy (TEM) images show that the agglomerates of nanoclay were broken down to form small particles consisting of several clay platelets. Fracture toughness of this epoxy system has been greatly enhanced with the addition of nanoclay. With the addition of only 4.5 phr of clay, the strain energy release rate of the epoxy is increased 5.8 times from the original value. Scanning electron microscope (SEM) was used to examine the characteristics of the fracture surfaces from the different materials. There is also significant reduction in the diffusivity and the maximum water uptake of the epoxy resin with the addition of the nanoclay.

Cure kinetic study of carbon nanofibers/epoxy composites by isothermal DSC

AbstractAn investigation was carried out into the cure kinetics of carbon nanofibers (CNF)/epoxy composites, composed of tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) resin and 4,4′‐diaminodiphenylsulfone (DDS) as a curing agent. The experimental data for both neat system and CNF/epoxy composites revealed an autocatalytic behavior. Analysis of DSC data indicated that the presence of carbon nanofibers had only a negligible effect on the cure kinetics of the epoxy. Kinetic analysis was performed using the phenomenological model of Kamal and two diffusion factors were introduced to describe the cure reaction in the latter stage. Activation energies and kinetic parameters were determined by fitting experimental data. Comparison between the two diffusion factors was performed, showing that the modified factor was successfully applied to the experimental data over the whole curing temperature range. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 329–335, 2005

Effect of irradiation with

AG-80 resin, namely tetraglycidyl diaminodiphenyl methane (TGDDM), is a new type of thermosetting matrix for advanced carbon/epoxy composites, which was irradiated with electrons of 160 keV. The results show that by increasing the fluence to 6.3×10 15 cm −2, the mass loss ratio ascends dramatically and then tends to level off. The mass loss behavior can be attributed to the combined effects of the formation of gaseous radiolytic products and a degraded layer, the surface ablation due to discharging and the skin carbon enrichment.

Cure Kinetics and Mechanical Properties of New Polyetherimide Toughened Epoxy Resin

The cure kinetics of blends of epoxy resin (4,4′-tetraglycidyl diaminodiphenyl methane; TGDDM)/curing agent (diaminodiphenyl sulfone; DDS) with ATPEI-CTBN-ATPEI triblock copolymer (ABA type) were studied using differential scanning calorimetry under isothermal conditions to determine the reaction parameters such as activation energy and reaction constants. By increasing the amount of ABA in the blends, the final cure conversion was decreased. Lower values of the final cure conversions in the epoxy/ABA blends indicated that ABA hinders the cure reaction between the epoxy and the curing agent. The value of the reaction order m for the initial autocatalytic reaction was not affected by blending ABA with epoxy resin, i.e., the value was approximately 1.0. The value of n for the n-th order component in the autocatalytic analysis was increased from 2.0 to 3.4 by increasing the amount of ABA in the blends. A diffusion controlled reaction was observed as the cure conversion increased and the curing reaction was successfully analyzed by incorporating the diffusion control term in the rate equation for the epoxy/DDS/ABA blends. The glass transition temperature of the cured blend was improved from 187 to 205°C and the value of the fracture toughness was also improved by about 400% compared to that of the unmodified resin at 30 wt% of ABA triblock copolymer. This is attributed to the formation of co-continuous morphology between the epoxy phase and ABA triblock copolymer phase. By increasing the amount of ABA, compressive strain, tensile stress and strain of the cured blends were increased, but the compressive stress was reduced due to the presence of CTBN rubbery phases.

Cure kinetics of carbon nanotube/tetrafunctional epoxy nanocomposites by isothermal differential scanning calorimetry

AbstractThe cure kinetics of tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) and 4,4′‐diaminodiphenylsulfone (DDS) as a cure agent in nanocomposites with multiwalled carbon nanotubes (MWNTs) have been studied with an isothermal differential scanning calorimetry (DSC) technique. The experimental data for both the neat TGDDM/DDS system and for epoxy/MWNTs nanocomposites showed an autocatalytic behavior. Kinetic analysis was performed with the phenomenological model of Kamal and a diffusion control function was introduced to describe the cure reaction in the later stage. Activation energies and kinetic parameters were determined by fitting experimental data. For MWNTs/epoxy nanocomposites, the initial reaction rates increased and the time to the maximum rate decreased with increasing MWNTs contents because of the acceleration effect of MWNTs. The values of the activation energies for the epoxy/MWNTs nanocomposites were lower than the values for the neat epoxy in the initial stage of the reaction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3701–3712, 2004

The kinetics and mechanism of cure of an amino-glycidyl epoxy resin by a co-anhydride as studied by FT-Raman spectroscopy

The thermal curing behavior of tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) and a co-anhydride mixture consisting of maleic anhydride (MA) and hexahydrophthalic anhydride (HHPA) was studied from 55 to 100 °C by real-time FT-Raman spectroscopy. The quantitative changes in concentrations of anhydride, epoxy, and new-formed ester were measured and empirical reaction rate curves were constructed reflecting the kinetics of the curing process. After an induction period a simple kinetic scheme that is first order in both epoxy and anhydride monomer consumption described the reaction profile until the reaction was influenced by chemo-rheological changes due to vitrification transition. FT-Raman analysis revealed that curing propagation mainly occurs by polyesterification between epoxide and anhydride. Possible side reactions including the homopolymerization of MA are considered. The main side reaction is decarboxylation of MA that may produces some autocatalysis, but this is a minor contribution to the kinetics of cure. No conclusive evidence has been found for homopolymerization of MA or initiation of the curing reaction by the reaction product of TGDDM and MA, compared to the polyesterification.

New tetrafunctional epoxy resin system with increased shelf life

AbstractChlorine‐ and methyl‐substituted aromatic diamines based on diaminodiphenylmethane were epoxidized and characterized. The effect of different substituents on epoxidation was studied. The cure studies of the two new tetrafunctional resins in comparison with unsubstituted resin N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) was carried out by DSC with 3,3′‐dichloro‐4,4′diaminodiphenylmethane (o‐DCDDM; 30% w/w) as a common curing agent. The mechanical properties such as flexural, Izod impact, heat distortion temperature (HDT), of such cured neat resins were also studied. The results of the cure studies indicate that the substitution of the α‐hydrogen of the resin by chlorine or methyl group decreases the reactivity of the resin leading to an increase in the shelf life. This study also indicates that the functionality of the resin plays a pivotal role in the reactivity and thus the shelf life of an epoxy resin system. The results of the mechanical properties of the neat resin casts obtained by subjecting to a common cure schedule when compared with the unsubstituted resin showed a decrease in impact strength, which is obvious because of the presence of a bulky pendant group but the impact strength was higher than that of the TGOS30 resin system. Results of flexural strength of the different substituted neat resin casts did not show much of a deviation from that of the unsubstituted resin system. The HDT results indicate no significant difference in the values of the unsubstituted resin vis‐a‐vis with substituted resin systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2790–2801, 2004

Influence of substituents on the kinetics of epoxy/aromatic diamine resin systems

AbstractEleven different epoxy/diamine systems, including tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM), triglycidyl p‐aminophenol (TGAP), and diglycidyl ether of bisphenol A (DGEBA) with 4,4′‐diaminodiphenylsulfone (DDS), diethyltoluenediamine (DETDA), dimethylthiotoluenediamine (DMTDA), and meta‐phenylenediamine (m‐PDA), were studied with near‐infrared spectroscopy at different temperatures. The reactivities of the epoxies were determined and found to be in the following order when reacted with the same amine: DGEBA > TGAP > TGDDM. When the primary amine was reacted with the same epoxy, the order was DETDA > DDS > DMTDA; for the secondary amine, the order was DETDA > DMTDA > DDS. The relative reaction rates of the secondary amine to the primary amine were compared and discussed in terms of the structural differences and the corresponding substitution effect. It was concluded that the increase in the secondary amine reactivity of DETDA and DMTDA was caused by the deconjugation of the benzene‐ring π electrons from the lone pair on the N atom. The overall order of the secondary amine relative reactivity was DMTDA > DETDA > DDS for the same epoxy and TGDDM > TGAP > DGEBA for the same amine. The m‐PDA systems had no significant positive or negative substitution effects. Molecular orbital calculations were performed, and the results showed the most significant deconjugation effect in the secondary amine of DETDA. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3143–3156, 2004

Processing and chemorheology of epoxy resins and their blends with dendritic hyperbranched polymers

AbstractToughened epoxy systems have found increasing applications in automotive, aerospace, and electronic packaging industries. The present article reported work done for elucidation of gelation and vitrification for various epoxy systems and their blends with dendritic hyperbranched polymers (HBPs) having epoxy and hydroxyl functionality. Gel time was found to increase with increasing functionality from diglycidyl ether of bisphenol A (DGEBA) to tetraglycidyl diaminodiphenyl methane (TGDDM). The vitrification point was clearly identified from rheological experiments for triglycidyl p‐amino phenol (TGAP) and TGDDM. In the case of DGEBA a clear display of vitrification was not observed. TGDDM underwent vitrification sooner than did TGAP. Hydroxyl‐functionalized HBP reduced the gel time of the blends because of the accelerating effect of –OH groups to the epoxy curing reaction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1604–1610, 2004

Quantitative structure–property relationships for composites: prediction of glass transition temperatures for epoxy resins

The glass transition temperatures of nine stoichiometric resin systems of tetraglycidyl-4,4′-diamino-diphenylmethane (TGDDM), triglycidyl p -amino phenol and diglycidyl ether of bisphenol A with 4,4′-diaminodiphenylsulphone (DDS), diethyl-toluenediamine and dimethylthiotoluenediamine were calculated using group interaction modelling (GIM) and atomic additivity (AA) methods. The input parameters were generated from kinetics simulation, which outputs the structure information for the cured systems. The modelling parameters were also applied to four non-stoichiometric systems of TGDDM and DDS. The predicted values from GIM were in good quantitative agreement with measured results from temperature modulated differential scanning calorimetry for all systems studied. Compared to GIM, the AA method gave inferior predictions for the highly crosslinked systems, especially for those, where epoxy was in excess.

Effect of organo‐phosphorus and nano‐clay materials on the thermal and fire performance of epoxy resins

AbstractThe results of flame retardance and thermal stability of a reactively modified organo‐phosphorus diglycidylether of bisphenol‐A and an organo‐phosphorus tetraglycidyl diaminodiphenylmethane are reported here. The organo‐phosphorus epoxy resins were synthesized by the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide and diglycidyl ether of bisphenol‐A and tetraglycidyl diaminodiphenylmethane, respectively, and then cured with a mixture of 3,5‐diethyltoluene‐2,4‐diamine and 3,5‐diethyltoluene‐2,6‐diamine. In addition to this, between 5 and 7.5% of organically modified polymeric layered silicate nano‐clay was also added to neat epoxy resin or to the phosphorus‐modified epoxy resin to investigate any synergies, or otherwise, a combination of clay and phosphorus on the flame, degradation, and thermal properties are also reported. The reaction kinetics of phosphorus‐modified and epoxy cure were studied by FTIR, 1H‐NMR, and DSC. Thermal properties and morphology of the final product were analyzed by thermogravimetric analysis, dynamic mechanical thermal analysis, X‐ray diffraction, and cone calorimetry. Improvement in flame retardance by cone calorimetry was demonstrated by the addition of only 3% phosphorus or 7.5% clay into the epoxy compared with unmodified epoxy resins, whereas no evidence of synergy for a phosphorus and clay combination was found. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1233–1253, 2004

Influence of phenyl-trisilanol polyhedral silsesquioxane on properties of epoxy network glasses

The influence of phenyl-trisilanol polyhedral silsesquioxane (POSS-triol) on the thermo-mechanical properties and curing of epoxy-amine networks were investigated using dynamic mechanical analysis (DMA) and Fourier transform infrared spectroscopy (FT-IR). Two of the most common epoxy monomers, diglycidyl ether of Bisphenol A (DGEBA), tetraglycidyl diamino diphenyl methane (TGDDM) were used. These epoxies were cured with linear aliphatic diamine: 2-Methyl-1,5-pentadiamine (Dytek ®A) or diamine terminated polypropylene oxide (Jeffamine ® D230). Using an identical curing schedule, when minor amounts of POSS-triol were added to the epoxy-amine networks, we found a significant improvement on value of T g. Due to the small quantity of POSS-triol used, this enhancement in T g is attributed to the catalytic activity of phenyl-trisilanol POSS in promoting a more completely cured epoxy network. This argument is consistent with observed increases in the rubbery plateau modulus due to increases in the crosslink density. But unlike other catalysts such as phenol, we did not observe acceleration of reaction in the pre-gelation stage by this acidic POSS-silanol. Because of its nanoscopic size, this acidic POSS-silanol promotes additional epoxy-amine crosslinking in the post-vitrification stage, which is dominated by diffusion-control mechanisms. We believe this can be utilized in fabrication of fiber-reinforced composites using the resin transfer molding process, where maintaining the low viscosity for a period of time is required to eliminate porosity and to produce higher T g materials at a lower post-cure temperature.

Development of a toughened DGEBS/DDS system toward improved thermal and mechanical properties by the addition of a tetrafunctional epoxy resin and a novel thermoplastic

AbstractIt was the object of the present article to discuss the effect of the addition of a tetrafunctional resin, namely, tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM), and of a novel 40:60 polyethersulfone:polyetherethersulfone (PES:PEES) copolymer on a blend constituted by a difunctional resin, diglycidyl ether of bisphenol S (DGEBS), and an aromatic ammine, 4,4′‐diaminodiphenylsulfone (4,4′DDS). The formulated blends were fully characterized in terms of the morphology and the viscoelastic and mechanical properties. The modification by the tetrafunctional resin was proved to be a useful means to improve the glass transition temperature and, therefore, to widen the range of the working temperature. The addition of the novel copolymer resulted in a marked increase in toughness without negatively affecting the thermal and elastic properties of the blend. TEM analysis, despite the high amount of thermoplastic used, showed a homogeneous morphology that would lead to the conclusion of the existence of a full‐IPN network. Moisture‐uptake experiments were conducted both on the blend and on the resins on their own. It was shown that the combination of the difunctional resin with the tetrafunctional led to a decrease of the percent of the water absorbed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 268–273, 2003

Layered silicate nanocomposites based on various high‐functionality epoxy resins: The influence of an organoclay on resin cure

AbstractThe influence of an organically modified clay on the curing behavior of three epoxy systems widely used in the aerospace industry and of different structures and functionalities was studied. Diglycidyl ether of bisphenol A (DGEBA), triglycidyl p‐amino phenol (TGAP) and tetraglycidyl diamino diphenylmethane (TGDDM) were mixed with an octadecyl ammonium ion modified organoclay and cured with diethyltoluene diamine (DETDA). The techniques of dynamic mechanical thermal analysis (DMTA), chemorheology and differential scanning calorimetry (DSC) were applied to investigate gelation and vitrification behavior, as well as catalytic effects of the clay on resin cure. While the formation of layered silicate nanocomposite based on the bifunctional DGEBA resin has been previously investigated to some extent, this paper represents the first detailed study of the cure behavior of different high performance, epoxy nanocomposite systems.

Thermal and mechanical characterisation of intercalated epoxy nanocomposites

Intercalated epoxy-layered silicate nanocomposites have been prepared using epoxy resins of varying functionalities. Diglycidyl ether of bisphenol A (DGEBA), triglycidyl p-amino phenol (TGAP) and tetraglycidyl diamino diphenylmethane (TGDDM) were mixed with 2.5–10 wt.-%; of an organophilic modified layered silicate and cured with diethyltoluene diamine. The d-spacing of the layered silicates in the cured resin system was determined by wide angle X-ray analysis. The catalytic influence of the clay on the bifunctional DGEBA system was investigated by differential scanning calorimetry (DSC). Dynamic mechanical thermal analysis (DMTA) was used to investigate the glass transition temperatures of the three different resin systems and therefore the changes in the network structure as a result of the incorporation of the clay content. Fracture measurements showed an increasing toughness of the nanocomposites with increasing clay content in all systems.

Separation of gelation from vitrification in curing of a fiber‐reinforced epoxy composite

AbstractPrepregs of a mixture of the tetrafunctional epoxy tetraglycidyl 4,4‐diaminodiphenyl methane (TGDDM) and the tetrafunctional amine 4,4'‐diaminodiphenylsulfone (DDS) were characterized with temperature‐modulated DSC (TMDSC) as well as dynamic mechanical analysis (DMA). The baseline shift of the glass transition was separated from the curing exotherm by using temperature‐modulated and step scan DSC temperature scans. Likewise, the baseline shift in heat capacity due to vitrification was isolated using TMDSC isotherms. Using the TMDSC glass transition temperature, degree of conversion, and vitrification results, combined with the gelation data generated from DMA, a time‐temperature‐transformation (TTT) diagram was constructed, providing information necessary for optimization of industrial processing of the epoxy prepreg. Thus, effects of storage, preprocessing, and postprocessing on the overall curing process are taken into account.

Cure Kinetic Model, Heat of Reaction, and Glass Transition Temperature of AS4/3501-6 Graphite–Epoxy Prepregs

A new isothermally-based, cure kinetic model for the carbon graphite–epoxy AS4/3501-6 prepreg is presented using an industrially supplied prepreg rather than the neat epoxy resin. A two-stage model is used: first, rate-controlled (autocatalytic); then diffusion-controlled. A Differential Scanning Calorimeter (DSC) is employed to investigate the prepreg’s cure kinetics using both isothermal and dynamic DSC scans, although only isothermal DSC scan data is used to fit the model’s parameters. A Thermogravimetric Analyzer (TGA) is used to determine the mass fraction of the epoxy resin in the prepreg. The coefficients are provided for a prepreg having 37.4% resin mass fraction; they must be re-evaluated for prepregs having significantly different resin mass fractions. The ultimate heat of reaction of the resin incorporated within the prepreg is measured as 433.7 J/g (based upon a linear baseline) or 422.7 J/g (based upon a specific-heat-corrected baseline) using dynamic DSC scans at 20°C/min. This value is 8–17% less than the reported 472–508 J/g for the neat 3501-6 epoxy also measured using dynamic DSC scans at 20°C/min. Important to manufacturing applications, dynamic DSC scans reveal that the prepreg’s ultimate heat of reaction is sensitive to scan rate. Finally, the prepreg’s carbon fiber and/or sizing appears to suppress the curing reaction and decrease the ultimate heat of reaction over that for the neat epoxy resin. The glass transition temperature Tg (°C) of partially-cured AS4/3501-6 prepregs is measured using DSC and is expressed as a function of degree of cure: Tg = 22.9 exp(2.16α) – markedly similar to 3501-6 neat resin Tg data measured earlier using a dynamic mechanical analyzer. The small specimen DSC thermal scans provide an effective means to measure the Tg of completely- or partially-cured prepregs. The Tg of the 100%-cured prepreg was experimentally determined to be 199°C, slightly higher than the 193°C reported for the 100%-cured neat epoxy resin. The AS4 fibers play little or no role in the degree-of-cure dependence of the AS4/3501-6 prepreg’s Tg. Recommended for general purpose structural applications, the AS4/3501-6 prepreg is composed of continuous, PAN-based, AS4C carbon (graphite) fibers and an amine-cured epoxy resin system. The epoxy resin, 3501-6, is a tetraglycidyl diamino diphenyl methane (TGDDM) with diaminodiphenylsulfone (DDS) catalyzed with boron trifluoride monoethylamine. 3501-6 was developed to operate in atemperature environment of up to 350°F (177°C).

Dynamic mechanical analysis of an epoxy/thermoplastic blend: polymerization‐induced phase separation

AbstractPhase separation behaviour and analysis of the morphologies for a commercial epoxy resin based on tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) with 4,4′‐diaminodiphenylsulfone (DDS) as hardener and blended with different amounts of poly(styrene‐co‐acrylonitrile) (SAN) thermoplastic, have been studied by dynamic mechanical analysis (DMA) supported by other techniques. In comparison with the neat system, the modified systems reach gelation and vitrification faster. These events have been assigned at the onset and the end of the storage modulus signals E′ in a DMA curve (E′ versus time). The results are explained by a phase‐separation phenomenon induced by polymerization. Scanning electron microscopy (SEM), focused on phase separation, has revealed a sea‐island type of morphology for low thermoplastic contents and an epoxy‐nodular or phase inverted structure for high thermoplastic contents.© 2002 Society of Chemical Industry

Maleimido-functionalized spirobislactone having enhanced volumetric expansion on polymerization

An approach to enhancing the volumetric expansion on polymerization of spirobislactone is proposed. This approach suggests a molecular modification of spirobislactone through attaching a rigid pendant segment bearing maleimido group to its aromatic ring. An additional volumetric expansion is achieved from loose molecular packing in cured resins due to the steric hindrance effect among rigid pendent segments. Thus a new monomer, maleimido-functionalized spirobislactone (MFS), is prepared. In order to evaluate the volumetric expansion of MFS during curing, tetraglycidyl 4,4′-diamino diphenyl methane (TGDDM) is employed to cure with MFS. The volumetric expansion of MFS on curing is measured to be 12.3%, higher than that of net spirobislactone monomer. The existence of loose molecular packing in MFS/epoxy cured resins is demonstrated by morphology observation of the cured resin stained by the phosphotungstic acid (PTA), and the stained regions are observed to be nanoparticles. Such a cured resin, prepared from 20 mol% of MFS and 80 mol% of TGDDM epoxy resin, shows excellent toughness (Charpy impact strength 13,000 J/m 2) and good mechanical strength (flexural strength 120 MPa, storage flexural modulus 4.2 GPa). Its glass transition temperature by dynamic mechanical thermal analysis (DMA) attains 227 °C, much higher than that of the cured resin from net spirobislactone and epoxy resin.