Tetraglycidyl Diaminodiphenyl Methane Research Articles

Morphology and properties of TGDDM/DDS epoxy systems toughened by amino-bearing phenyl silicone resins

A series of amino-bearing phenyl silicone resins (APSR) were synthesized for toughening the tetraglycidyl 4,4′-diaminodiphenyl-methane (TGDDM) epoxy resin cured with 4,4′-diamino diphenyl sulfone. The microstructure of the TGDDM/APSR resins was highly dependent on the amino content of APSR and the loading level of the modifier. Based on the SEM and TEM studies, microstructure evolution of the TGDDM/APSR resins in the curing process was imaged. The toughness of the TGDDM resin was effectively improved without sacrificing the tensile strength, the flexural strength, and the modulus. The thermal stability and water resistance were improved as well. However, the modifier brought in a noticeable lowering in the glass transition temperature.

Cure and thermal stability of poly(amide‐amidic acid)—cured tetraglycidyl 4,4′‐diaminodiphenylmethane

AbstractA novel curing agent, poly (amide‐amidic acid) (PAA), was used to cure tetraglycidyl 4,4′‐diaminodiphenylmethane (TGDDM). The initial cure and exothermic peak temperatures increased with increase in PAA content. The mechanism for the cure of TGDDM/PAA was proposed which involved, besides TGDDM cure, PAA imidization in the system. Examination of the morphology of the fractured surface using scanning electron microscopy showed that curing with PAA improved more the fracture toughness as compared to the conventional 4,4′‐diaminodiphenylsulfone (DDS), and rendered TGDDM more fire resistant with higher char yield. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

ISOTHERMAL CURING BEHAVIORS OF EPOXY/GRAPHITE OXIDES NANOCOMPOSITES

The cure kinetics of N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane(TGDDM) and 4,4′-diaminodiphenylsulphone(DDS) nanocomposites filled with graphite oxide(GO) was studied by isothermal differential scanning calorimetry(DSC).Furthermore,the functional groups on the surface of GO and their influence on the cure behaviors of TGDDM/DDS/GO nanocomposites were studied by X-ray photoelectron spectroscopy(XPS) and Fourier-transform infrared spectroscopy(FTIR),and the thermal stabilities of the neat graphite and GO were compared by thermalgravitimetric analysis(TGA).The XPS,FT-IR and TGA results showed that there were large numbers of polar functional groups such as hydroxyl,carboxyl and cyclic epoxide groups on the surface of GO,which effected the cure behaviors of TGDDM/DDS/GO nanocomposites.The experimental data of the isothermal DSC for both the neat TGDDM/DDS system and its GO nanocomposites showed an autocatalytic behavior.Furthermore,with the increase of GO contents,the time to the maximum cure rate decreased whereas the initial cure rate increased with the increase of GO contents,which indicated that GO catalyzed the cure reaction of epoxy.The apparent activation energy for the initial stage of the reaction(E1) of TGDDM/DDS/GO nanocomposites obtained by Kamal's model decreased first and then increased with the increase of GO contents,while the apparent activation energy for the reaction after the initial autocatalytic stage(E2) slight decreased with the increase of GO contents.Good agreement between the experimental data and the autocatalytic model with the modified diffusion factor in the later stage of cure was found over the whole curing temperature range for all of the neat epoxy resin and its nanocomposites with GO.The results showed that the incorporation of GO accelerated the cure reaction of the TGDDM/DDS system at lower GO content due to the interaction between the functional groups on the surface of GO and the epoxy resin.

Development of novel TGDDM epoxy nanocomposites for aerospace and high performance applications – Study of their thermal and electrical behaviour

The present work focuses on a study of the thermal and electrical behaviour of pure N,N′-tetraglycidyl diaminodiphenylmethane (TGDDM) for use in aerospace, high performance applications. The synthesis of the tetraglycidyl epoxies was done and they were characterized by FT-IR (Fourier transform infrared spectra) and Nuclear magnetic resonance spectra (1H NMR and 13C NMR). Nanoclay and POSS-amine nanoreinforcements denoted as N1 and N2 were incorporated into the synthesized epoxy resins. Curing was done with diaminodiphenylmethane (DDM) and bis(3-aminophenyl)phenylphosphine oxide (BAPPO) curing agents denoted as X and Y, respectively. The thermal behaviour of the tetraglycidyl resins and their corresponding nanocomposites was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The electrical behaviour namely dielectric strength, comparative tracking index (CTI), volume resistivity, surface resistivity and arc resistance of the nanocomposites was also studied and the interesting results obtained are discussed.

Synthesis and characterization of organic-inorganic hybrid clay filled and bismaleimide—siloxane modified epoxy nanocomposites

Organic-inorganic hybrids involving organo-modified montmorillonite (OMMT) clay and tetraglycidyl diamino diphenyl methane epoxy (TGDDM) were prepared via in situ polymerization by the homogeneous dispersion of various percentages (1–5% w/w) of clay in epoxy matrix resin. The resulting homogeneous epoxy—clay hybrids were modified with 10 wt% of hydroxyl terminated polydiemthyl siloxane (HTPDMS) using γ—aminopropyltriethoxysilane (γ-APS) as coupling agent in the presence of tin catalyst. The siliconized epoxy-clay prepolymers were further modified separately with 15 wt% of bismaleimide (BMI) monomers and cured with diaminodiphenylmethane. The reactions involved during the curing process between epoxy resin, siloxane and BMI were confirmed by using FTIR and DSC curing analysis. The differential scanning calorimetry (DSC) show that the significant increase in glass transition temperatures in the clay filled hybrid epoxy systems than that of neat epoxy resin. The data obtained from thermal studies indicates that the appreciable improvement in hybrid systems was due to the incorporation of MMT clay, BMI and siloxane into epoxy systems. Scanning electron microscopy (SEM) of the hybrid systems show that the homogenous morphology. X-ray diffraction analysis of the clay hybrid systems shows that the amorphous diffraction patterns and the peaks are broadened and nearly disappeared after 24 h swelling, suggesting the formation of exfoliated structure.

Octasilsesquioxane-reinforced DGEBA and TGDDM epoxy nanocomposites: Characterization of thermal, dielectric and morphological properties

Epoxy resin nanocomposites, based on the diglycidyl ether of bisphenol-A (DGEBA) and tetraglycidyl diamino diphenyl methane (TGDDM), are prepared via in situ co-polymerization with 4,4′-diaminodiphenylsulfone (DDS) in the presence of octa-aminophenyl silsesquioxane (OAPS) at levels of up to 20 wt.% of the latter. The curing reaction involving epoxy, DDS and OAPS is investigated using Fourier transform infrared (FTIR) spectroscopy. Differential scanning calorimetry and dynamic mechanical analysis show that the glass transition temperatures of the polyhedral oligomeric silsesquioxane (POSS) containing nanocomposites are higher than the corresponding neat epoxy systems at lower concentrations of POSS (⩽3 wt.%). Thermogravimetric analysis indicates that the POSS–epoxy nanocomposites display high ceramic yields, suggesting improved flame retardancy. The increasing concentration of OAPS into epoxy–amine networks exhibits a decreasing trend in the values of dielectric constant compared with those values obtained from neat epoxy systems. The higher epoxy functionality present in TGDDM leads to nanocomposites which possess enhanced thermal stability and higher dielectric constants than the DGEBA-based nanocomposites. X-ray diffraction analysis reveals that the molecular level reinforcement of POSS cages occurs in both the cases of DGEBA- and TGDDM-based hybrid epoxy nanocomposites. Furthermore, homogeneous dispersion of POSS cages in the epoxy matrices is evidenced by scanning electron microscopy, which further confirms that the POSS molecule has become an integral part of the organic–inorganic inter-cross-linked network systems.

CURE KINETICS OF TGDDM/DDS SYSTEM STUDIED BY NON-ISOTHERMAL METHOD

4,4′-tetraglycidyldiaminodiphenyl methane (TGDDM) epoxy resins are widely used in the fields of aviation and airspace owing to their excellent properties,but the physical properties of the cured epoxy resins depend on their structure,the extent of cure,the curing conditions,the time and temperature of cure.So it is necessary to study the curing kinetics in order to obtain the optimal curing process.The Curing kinetics of TGDDM in presence of 3,3′-diaminodiphenylsylfone (DDS) as the curing agent was studies by differential scanning calorimetry (DSC) technique at different heating rates.The kinetic mechanism functioin was determined using n order reaction and the most probability mechanism functioin method given by Malek respectively,the kinetic parameters of curing reaction were determined with the kinetic analysis of the data obtained by the thermal treatment,then the kinetic model was built.The results indicated that the n order model deduced from Kissinger and Crane equation,by which the parameters of curing reaction,the reaction order and activity energy were obtained,had great distinction with the experimental data.While the Malek analytical mechanism showed that the curing process of the curing reactions followed an autocatalytic reaction.The two-parameter (m,n) autocatalytic model can well describe the curing reaction processs of the studied epoxy resins.The DSC curves obtained using the experimental data showed a good agreement with that theoretically calculated under 5～20 K/min heating rate.The research results will provide theoretical basis for the choice of manufacturing process and the optimization of processing window.

Thermal and mechanical properties of a dendritic hydroxyl‐functional hyperbranched polymer and tetrafunctional epoxy resin blends

AbstractBlends of a tetrafunctional epoxy resin, tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM), and a hydroxyl‐functionalized hyperbranched polymer (HBP), aliphatic hyperbranched polyester Boltorn H40, were prepared using 3,3′‐diaminodiphenyl sulfone (DDS) as curing agent. The phase behavior and morphology of the DDS‐cured epoxy/HBP blends with HBP content up to 30 phr were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The phase behavior and morphology of the DDS‐cured epoxy/HBP blends were observed to be dependent on the blend composition. Blends with HBP content from 10 to 30 phr, show a particulate morphology where discrete HBP‐rich particles are dispersed in the continuous cured epoxy‐rich matrix. The cured blends with 15 and 20 phr exhibit a bimodal particle size distribution whereas the cured blend with 30 phr HBP demonstrates a monomodal particle size distribution. Mechanical measurements show that at a concentration range of 0–30 phr addition, the HBP is able to almost double the fracture toughness of the unmodified TGDDM epoxy resin. FTIR displays the formation of hydrogen bonding between the epoxy network and the HBP modifier. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 417–424, 2010

Spectroscopic, Mechanical and Dynamic‐Mechanical Studies on the Photo‐Aging of a Tetrafunctional Epoxy Resin

AbstractThe photo‐oxidative degradation of a densely cross‐linked epoxide/diamine network based on tetraglycidyl‐4,4′ diaminodiphenylmethane (TGDDM) and 4,4′ diaminodiphenyl sulphone (DDS) has been investigated by FTIR spectroscopy, dynamic‐mechanical analysis (DMA) and compressive mechanical tests. The FTIR measurements allowed us to monitor the degradation process of the different groups present in the TGDDM/DDS network and to obtain reliable kinetic data. On this basis the most likely photo‐degradation mechanisms were proposed. Dynamic‐mechanical measurements and mechanical compressive tests were used to gain an insight in the effect of the photo‐oxidative degradation on the relaxation processes of the epoxy network and on the mechanical performances.

Study on thermoplastic-modified multifunctional epoxies: Influence of heating rate on cure behaviour and phase separation

The effect of heating rate on the cure behaviour and phase separation of thermoplastic-modified epoxy systems was investigated. Polyethersulphone (PES) modified multifunctional epoxies, triglycidyl-aminophenol (TGAP) and tetraglycidyldiaminodiphenylmethane (TGDDM), as well T300/914 prepreg were used. It was shown that heating rate had a significant influence on the cure kinetics and phase structures of investigated systems. Greater heating rate causes higher epoxy conversion. The domain size of the macrophases formed from phase separation increases with the increase of heating rate. A more complete phase separation is achieved by fast heated thermoplastic-modified epoxy blends.

Hierarchical modelling of a polymer matrix composite

A hierarchical modelling scheme to predict the properties of a polymer matrix composite is introduced. The stress–strain curves of amine-cured tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) cured have been predicted using group interaction modelling (GIM). The GIM method, originally applied primarily to linear polymers, has been significantly extended to give accurate, consistent results for TGDDM, a highly crosslinked two-component matrix. The model predicts a complete range of temperature-dependent properties, from fundamental energy contributions, through engineering moduli to full stress–strain curves through yield. The predicted properties compare very well with experiment. Using the GIM-predicted TGDDM stress–strain curve, a 3D finite element model is used to obtain strain concentration factors (SCF) of fibres adjacent to a fibre break in a unidirectional (UD) composite. The strain distribution among the intact neighbouring fibres is clearly affected by the yielding mechanism in the resin matrix. A Monte Carlo simulation is carried out to predict the tensile failure strain of a single composite layer with the thickness equal to the fibre ineffective length. The effect of matrix shear yielding is introduced to the model through the SCF of surviving fibres adjacent to the fibre-break. The tensile failure strain of the composite is then predicted using a statistical model of a chain of composite layers.

THERMOANALYTICAL STUDIES OF HIGH PERFORMANCE EPOXY/CARBON NANOTUBE COMPOSITES

Carbon nanotubes (CNTs) have outstanding characteristics including high mechanical properties,namely tensile strength and elastic modulus,and still remarkable flexibility,excellent thermal and electric conductivities,low percolation thresholds (loading weight at which a sharp drop in resistivity occurs) and high aspect ratios (length to diameter ratio,L/D),while the latter provides the nanotubes with additional advantage over spherical fillers to obtain high property composites.Therefore,CNTs have the potential to act as a reinforcing filler of polymer matrices.The tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) cured with 4,4′-diaminodiphenylsulphone (DDS) and filled with graphite or carbon fibers are commonly used as a polymeric matrix in high performance composites employed in the aircraft and spacecraft industries.In present paper,multi-walled carbon nanotubes (MWNTs) as a nano-filler were incorporated in the TGDDM/DDS epoxy.The thermal properties of the composites were studied by differential scanning calorimetry (DSC),dynamic thermal analysis (DMTA) and thermalgravitimetric analysis (TGA).In addition,the dispersion of MWNTs in the epoxy was also investigated by scanning electron microscopy (SEM).In DSC studies,Kissinger and Flynn-Wall-Ozawa (FWO) methods were used to study the nonisothermal cure kinetics of the MWNTs filled TGDDM/DDS composites at different heating rates.The activation energy (E_a) of cure reactions of the MWNTs filled epoxy composites was obtained by Kissinger and FWO methods.For all composites,the E_a obtained by Kissinger method was slightly less than that of FWO method.With the addition of MWNTs,the E_a of the epoxy composites decreased first and then increased with the increase of the MWNTs contents.These results showed that the incorporation of carbon nanotubes accelerated the cure reaction of the TGDDM/DDS epoxy at lower MWNTs content due to the interaction between the hydroxyl groups on the surface of nanotubes and the epoxy.However,due to the high surface energy of carbon nanotubes,the viscosity of MWNTs/epoxy composites increased at higher MWNTs content.Hence,the mobility of hydroxyl groups was hindered,and the reaction energy of composites increased with increasing MWNTs contents.The influence of carbon nanotubes on the thermal stability of the epoxy was studied by TGA.It is shown that MWNTs had little influence on the thermal stability of the cured epoxy.The storage modulus and glass transition temperature of MWNTs filled TGDDM/DDS were investigated by DMTA.It is seen that the storage modulus of TGDDM/DDS system was enhanced with the increasing of MWNTs content,that is,the modulus increased 6.3% and 7.8% at 1 wt% and 5% MWNTs content,respectively.The glass transition temperature of the epoxy slightly decreased.Furthermore,the DMTA results of MWNTs/TGDDM/DDS composites were compared with that of carbon nanofibers (CNFs)/TGDDM/DDS composites.It was shown that the interactions between CNFs and epoxy were better those between that MWNTs and epoxy.The dispersion of carbon nanotubes in the epoxy was studied by SEM.The SEM results suggest that of MWNTs had poor dispersion in the cured epoxy.However,the radii of carbon nanotubes in the epoxy were greater than those of pure nanotubes.These results show the existence of interaction between carbon nanotubes and epoxy.

Epoxy/polyhedral oligomeric silsesquioxane (POSS) hybrid networks cured with an anhydride: Cure kinetics and thermal properties

A new class of organic–inorganic hybrid networks was prepared via copolymerization of octakis(dimethylsiloxybutyl epoxide)octasilsesquioxane (OB), N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenyl methane (TGDDM) and hexahydrophthalic anhydride (HHPA). Kinetic studies show that even with 1H-imidazole as the catalyst, the rate for the curing of OB/HHPA is still significantly higher than that for TGDDM/HHPA in the temperature range studied. Two-stage reactions were thus carried out to allow OB to react with HHPA first (Stage I). The glass transition temperature (Tg) of the networks was found to be strongly dependent on Stage I reaction since too short a reaction time caused poor bonding of OB to the networks while too long a reaction time led to the formation of OB oligomers that de-homogenized the networks. With 5mol.% OB, the hybrid prepared via the optimized two-stage reaction displayed a large jump of ∼20°C in Tg, which was accompanied by slight improvements in thermal degradation temperature and storage modulus, as compared to TGDDM/HHPA.

Thermodynamic and mechanical properties of amine-cured epoxy resins using group interaction modelling

The prediction of thermal and mechanical properties of amine-cured epoxy resins by group interaction modelling is presented. The derivation of the group interaction based approach to the prediction of macroscopic engineering properties of both linear and crosslinked epoxy resins is described with specific application to MY721 resin. The glass transition temperature, bulk and tensile modulus and linear thermal expansion coefficient of tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) cured with 4,4′-diaminodiphenyl sulphone (DDS) are estimated using the model and compared with results from dynamic mechanical experiments. The glass transition of TGDDM/DDS is calculated to occur at approximately 248 °C and the reasons for a secondary peak in the spectrum cured to 180 °C are given. The bulk and tensile modulus of TGDDM/DDS are calculated to be 7.54 GPa and 5.34 GPa, respectively.

Effect of type of substitution in 4,4′‐bis‐(diaminodiphenyl) methane hardener on cure kinetics, mechanical, and flame retardant properties of tetrafunctional epoxy resins

AbstractThe nature of the substituent in 4,4′‐bis‐(diaminodiphenyl) methane (DDM) hardener on the cure kinetics, mechanical, and flame retardant properties of N,N,N′,N′‐tetraglycidyl diaminodiphenyl methane (TGDDM) resin is investigated in comparison with unsubstituted DDM and widely used 4,4′‐bis‐(diaminodiphenyl) sulfone hardeners. Dynamic differential scanning calorimetry (DSC) and cure rheology studies showed that the substitution decreased the reactivity of the amine. An electron‐withdrawing chlorine substituent was found to be more effective than an electron‐releasing methyl group in reducing the amine reactivity. Substituted and unsubstituted DDM hardeners showed two peaks in their DSC thermograms that were due to steric hindrance in the former and deficiency of amine in the latter. Substitution showed its effect on the mechanical properties and glass‐transition temperature. The flexural modulus was increased; however, the Izod impact and glass‐transition temperature were decreased in substituted amine systems. The limiting oxygen index results showed higher flame retardancy in the chlorine substituted hardener system compared to other hardener systems that were studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 480–491, 2006

Chemistry of thermal ageing in aerospace epoxy composites

AbstractThe detailed chemical reactions involved in the thermal ageing (at 120°C) of a typical aerospace epoxy composite have been studied by the mid‐Fourier transform infrared spectroscopy (FTIR) spectral characterization of selected model compounds. The FTIR spectra indicate that at this particular temperature, the major reaction in the resin structure is probably an oxidation of a CH2 group adjacent to the nitrogen atom of the tetraglycidyldiaminodiphenyl methane unit of the molecular structure, particularly where it is attached to one isomer of the diaminodiphenylsulfone hardener unit. The FTIR changes indicate that the major product is an amide group but other minor changes are also detailed and differences in the chemical changes seen at other ageing temperatures highlighted. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2210–2219, 2006

Rheokinetic and Dynamic Mechanical Analysis of Tetrafunctional Epoxy/anhydride Mixtures. Influence of Stoichiometry and Cure Conditions

The copolymerization of hexahydrophthalic anhydride (HHPA) with N, N, N′, N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) has been studied for several stoichiometric ratios. The rheological, thermal and dynamic mechanical behaviors of these systems were examined. Kinetic studies by differential scanning calorimetry, in both isothermal and dynamic modes, showed a first-order kinetics. Activation energies were also obtained by rheological measurements, through gelation times at different temperatures, with results in agreement with calorimetric results. The dynamic mechanical behavior was studied to analyse the influence of both stoichiometric ratio and cure schedule in the viscoelastic properties of the mixtures.

Thermal characterization of carbon‐nanofiber‐reinforced tetraglycidyl‐4,4′‐diaminodiphenylmethane/4,4′‐diaminodiphenylsulfone epoxy composites

AbstractThe thermal properties of carbon nanofibers (CNF)/epoxy composites, composed of tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) resin and 4,4′‐diaminodiphenylsulfone (DDS) as a curing agent, were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis, and dynamic mechanical thermal analysis. DSC results showed that the presence of CNF had no pronounced influence on the heat of the cure reaction. However, the incorporation of CNF slightly improved the thermal stability of the epoxy. Furthermore, the storage modulus of the TGDDM/DDS epoxy was significantly enhanced, whereas the glass‐transition temperature was not significantly affected, upon the incorporation of CNFs. The storage modulus of 5 wt % CNF/epoxy composites at 25°C was increased by 35% in comparison with that of the pure epoxy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 295–298, 2006

Investigation of the reaction mechanism of different epoxy resins using a phosphorus‐based hardener

AbstractIn this work, the fundamental kinetic and structure/property information for a novel phosphorus‐based hardener, bis(4‐aminophenoxy) phosphonate is cured with a range of common epoxy resins such as diglycidyl ether of bisphenol A, tri glycidyl p‐amino phenol and tetra glycidyl diamino diphenyl methane (TGDDM) at various cure temperatures. The rate coefficients k1 and k2 for the primary and secondary amine epoxide addition reactions, respectively, were determined and were found to exhibit a positive substitution effect for the TGAP and TGDDM epoxy resins. Etherification or internal cyclization were shown to be important at higher levels of cure conversion, with these reactions being more significant for the TGAP/BAPP system. Some basic structure/property relationships were established between the glass transition temperature (Tg) and epoxide conversion. The master curve obtained for the superimposition of the various cure temperatures for each epoxy demonstrated the independence of the cure mechanism with temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99:3288–3299, 2006

Damage effects of 120‐keV electron radiation on AG‐80 resin

AbstractAG‐80 epoxy resin, namely tetraglycidyl diaminodiphenyl methane (TGDDM), was irradiated with electrons of 120 keV. The results show that the irradiation leads to four major damage effects on the surface layer of the AG‐80 resin, including the discharging, mass loss, degradation, and carbon enrichment. With increasing fluence to 1.05 × 1016 cm−2, the mass loss ratio increases gradually, and then tends to level off. The mass loss behavior can be attributed to a combined effect of the formation of gaseous radiolytic products and a degraded layer, the surface ablation due to discharging, and the skin carbon enrichment. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 177–184, 2006