Diaminodiphenylmethane Epoxy Research Articles

Fully aminated rigid‐rod aromatic polyamide efficiently reinforces tetraglycidyl diamino diphenyl methane epoxy resin and its carbon fiber composite

AbstractTetraglycidyl diamino diphenyl methane (TGDDM) and its carbon fiber composite are widely studied and used because of their heat resistance and high performance. In order to obtain efficient reinforcing effects in a simple manner, we adopt the idea of molecular composite—uniformly dispersing the rigid‐rod macromolecules in the TGDDM matrix. Herein, we prepared fully aminated‐poly(p‐phenylene terephthalamide) by direct polycondensation and hydrogenation reduction as the reinforcing agent. The fully aminated‐PPTA is distributed uniformly in the cross‐linked epoxy resin (EP) network by chemical bonds, and achieves efficient reinforcement. With the addition of only 0.5 wt% fully aminated‐PPTA, the tensile strength and Young's modulus of EP are improved to 127.7 ± 7.4 MPa (+28%) and 3.36 ± 0.15 GPa (+44%); the flexural strength and modulus are improved to 209.6 ± 9.4 MPa (+42%) and 3.70 ± 0.14 GPa (+37%); the notch impact strength is improved by 32%. Crucially, the heat resistance of EP almost remains unchanged. Furthermore, the flexural properties and interlaminar shear strength of the carbon fiber composite are also comprehensively increased. Compared with other modified fillers, the fully aminated‐PPTA is simple to prepare and blend, and is an efficient reinforcing agent for TGDDM and its carbon fiber composite benefitting from its rigid‐rod main chain and amino side groups.Highlights Molecular composite can achieve excellent strengthen and toughen effects. Fully aminated‐PPTA is embedded uniformly in EP network by chemical bonds. TGDDM is effectively reinforced without deteriorated heat resistance. Fully aminated‐PPTA is also a comprehensive reinforcement for EP/CF composite.

Synthesis and characterization of epoxy resin composites modified by reactive polyimide containing hydroxyl groups

Reactive polyimide (PI) containing phenolic hydroxyl groups was prepared by the polymerization of 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane and mixed thiodiphthalic anhydride. A series of epoxy resin composites were obtained by adding reactive PI to N,N,N′,N′-tetraglycidyl-4,4′-diamino-diphenylmethane (TGDDM) epoxy resin in different proportions. The effect of PI content on curing behavior, thermal properties, and mechanical properties was carefully investigated. Even a small amount of PI addition improved the mechanical properties and heat resistance of the epoxy resin, particularly the fracture toughness. Among them, epoxy resin composites EP-PI-1.5 with the addition of 1.5 wt% PI showed the best mechanical properties, whose impact strength, fracture toughness, and tensile strength were increased by 114%, 59%, and 34%, respectively. The phase morphology was also investigated to illustrate the fracture mechanism by scanning electron microscope (SEM) characterization.

Effects of Proportion of BF3-MEA on Curing Properties of AG-80/DDS Resin System

Through differential scanning calorimeter (DSC), the systematic analysis is carried out on the issues including: the curing properties of the resin system composed of 4,4’-diaminodiphenylmethane epoxy resin (AG-80), 4,4’-diaminodiphenylsulfone (DDS) and boron trifluoride monoethylamine complex (BF3-MEA); the effect imposed by the varying content of BF3-MEA on the temperature, extent and rate of reaction; and the effect imposed by the varying DSC heating rates on the curing properties of the AG-80/DDS/BF3-MEA resin system. In the meantime, Ti0, Tp0 and Tf0 are derived, and the curing regimes of the three proportioning schemes are determined accordingly. The gel time of the AG-80/DDS/BF3-MEA resin system is measured through the gel drawing method, and the effect of the BF3-MEA content on the gel time is assessed, so as to determine that 0.7 times of the gel time shall be the pressure time for the forming of composite materials. Furthermore, tests are carried out on the mechanical properties of the resin cast and the carbon fiber composite materials prepared through the three proportioning schemes. The results have shown that when the content of BF3-MEA is 2%, the AG-80/DDS/BF3-MEA resin system outperforms the other proportioning schemes in terms of the curing process and the processability of its composite materials. Besides, the comprehensive mechanical properties of the resin cast and the carbon fiber composite are better.

Mechanical properties of reactive polyetherimide-modified tetrafunctional epoxy systems

Highly crosslinked multifunctional epoxy resins are commonly brittle. Thermoplastic toughening agents have been used to improve the fracture toughness of crosslinked epoxy resins. However, toughness improvement is limited due to poor interfacial adhesion between epoxy matrix and thermoplastic toughener. Furthermore, it is desired that toughness improvements should not come at the expense of other properties, including modulus, thermal properties and processability. In this work, amine functionalized reactive polyetherimide (rPEI) having two different molecular weights and loading levels were incorporated in tetraglycidyl-4, 4′-diaminodiphenyl methane (TGDDM) epoxy resin to study the structure-property relationship, including effects of reaction-induced phase separation on fracture toughness. Results demonstrate that the phase morphologies of rPEI in an epoxy resin can be drastically affected by the functionality, molecular weight and loading levels of rPEI. The mode-I fracture toughness (KIC) of rPEI-toughened epoxy is increased by up to 140% versus untoughened epoxy control. An investigation into the fracture mechanisms of rPEI-toughened TGDDM epoxy showed evidence of rPEI particle bridging as one of the key mechanisms of toughening. Our work further demonstrated that the rPEI-toughened TGDDM epoxy maintained both high modulus and high Tg, rendering it suitable for a wide range of applications.

Bonding mechanism on TGDDM/CF and the influences of functional groups and interfacial water: An MD and DFT investigation

Bonding mechanism between tetraglycidyl diamino diphenyl methane (TGDDM) epoxy resin and carbon fiber (CF) is investigated by employing MD and DFT methods. Edge sites of CF surface (CF(100) and (110)) are focused due to they are chemically active than the inert basal planes. Two kinds functional groups (OH and COOH) are anchored on these sites, and the impacts of interfacial water are examined. The most negative adsorption energy (Ead) goes to the model of TGDDM absorbed onto COOH-functionalized CF(110) (noted as CF(110)COOH). Mulliken population analysis implies that O-H hydrogen bonds have formed across the interface. More bonds tend to form with CF(110) surface and COOH groups. The energy per each hydrogen bond is around 25.95–31.07 kJ/mol, and bond length ranges around 1.81–2.49 Å, which are consistent with previous reports. For the interfacial bonds associated with OH-functionalizaion, TGDDM and OH groups are hydrogen acceptors and donors, respectively. While for the cases with COOH groups, both the TGDDM and COOH groups can act as either acceptors, or donors. Caused by interfacial water, the interfacial hydrogen bonds will be detached, and the interaction energy (Eint) between TGDDM-CF(110) decreases 84.04%. Meanwhile, new hydrogen bonds will form between H2O-TGDDM (and H2O-CF).

Effect of the Aromatic Amine Curing Agent Structure on Properties of Epoxy Resin-Based Syntactic Foams.

Epoxy resin is one of the commonly used matrixes of syntactic foams as a buoyancy material, the curing agents of which affect some of the properties for syntactic foams. Therefore, the curing reactions of N,N,N′,N′-tetraepoxypropyl-4,4′-diaminodiphenylmethane (AG-80) epoxy resin between 4,4-diaminodiphenyl methane (DDM) and the mixture of m-xylylenediamine and DDM (DDM-m-XDA) systems are studied. The DDM mixed with m-XDA enhances curing reactions with the AG-80 epoxy resin, and the mechanisms of the two curing systems are different through nonisothermal kinetics. Compared with a single curing system, there are some wrinkles on the surface of the AG-80/DDM-m-XDA matrix because of the disordered network. Composited with hollow glass microspheres (HGMs), the more flexible m-XDA structure enhances the interfacial adhesion between the matrix and HGM for syntactic foams. However, the wrinkles in the matrix increase the broken degree of HGMs; especially at HGM contents higher than 55%, the flaw increases the density and water absorption of syntactic foams; meanwhile, it decreases the compressive strength. Therefore, the properties of syntactic foams can be improved by mixing different molecular structure curing agents and the mixture liquid curing agent simplifies the preparation process to some extent.

Tetrafunctional Epoxy Resin-Based Buoyancy Materials: Curing Kinetics and Properties.

In order to synthesize a new kind of buoyancy material with high-strength, low-density and low-water-absorption and to study the curing reaction of tetraglycidylamine epoxy resin with an aromatic amine curing agent, the non-isothermal differential scanning calorimeter (DSC) method is used to calculate the curing kinetics parameters of N,N,N′,N′-tetraepoxypropyl-4,4′-diaminodiphenylmethane epoxy resin (AG-80) and the m-xylylenediamine (m-XDA) curing process. Further, buoyancy materials with different volume fractions of hollow glass microsphere (HGM) compounded with a AG-80 epoxy resin matrix were prepared and characterized. The curing kinetics calculation results show that, for the curing reaction of the AG-80/m-XDA system, the apparent activation energy increases with the conversion rates increasing and the reaction model is the Jander equation (three-dimensional diffusion, 3D, n = 1/2). The experimental results show that the density, compressive strength, saturated water absorption and water absorption rate of the composite with 55 v % HGM are 0.668 g·cm−3, 107.07 MPa, 0.17% and 0.025 h−1/2, respectively. This kind of composite can probably be used as a deep-sea buoyancy material.

Curing and Characteristics of N,N,N′,N′-Tetraepoxypropyl-4,4′-Diaminodiphenylmethane Epoxy Resin-Based Buoyancy Material

Buoyancy material is a type of low-density and high-strength composite material which can provide sufficient buoyancy with deep submersibles. A new buoyancy material with N,N,N′,N′-tetraepoxypropyl-4,4′-diaminodiphenylmethane epoxy resin (AG-80) and m-xylylenediamine (m-XDA) curing agent as matrix and hollow glass microsphere (HGM) as the filler is prepared. The temperature and time of the curing process were determined by the calculations of thermal analysis kinetics (TAK) through differential scanning calorimetry (DSC) analysis. The results show that the better mass ratio of AG-80 with m-XDA is 100/26. Combined TAK calculations and experimental results lead to the following curing process: pre-curing at 75 °C for 2 h, curing at 90 °C for 2 h, and post-curing at 100 °C for 2 h. The bulk density, compressive strength, and saturated water absorption of AG-80 epoxy resin-based buoyancy material were 0.729 g/cm3, 108.78 MPa, and 1.23%, respectively. Moreover, this type of buoyancy material can resist the temperature of 250 °C.

Critical absorbed dose of resinous adhesive material towards non-destructive chemical-state analysis using soft X-rays

The local electronic state of the N,N,N',N'-tetraglycidyl-4,4′-diaminodiphenylmethane epoxy resin cured with 4,4′-diaminodiphenylsulfone (TGDDM-DDS), one of model adhesive materials, was investigated by the O K-edge X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES). The total-electron-yield XAS spectra for TGDDM-DDS as a function of the X-ray dose exhibit the exponential-like decrease in the curing-derived pre-edge intensity due to the radiation damage. The quantitative analysis on the pre-edge intensity with respect to the X-ray dose enables the determination of the critical absorbed dose for the chemical change on TGDDM-DDS as 3.83 ± 0.01 MGy at 300 K. By using resonant XES with the well-focused X-ray beam, we found that (i) the charged-particle equilibrium exists for the soft X-rays in the range of at least 0.001–0.847 mm2 beam spot and that (ii) the half of the critical absorbed dose can be regarded as the limit indicator for the non-destructive chemical-state characterization on resinous adhesive materials and interfaces using soft X-rays.

Ultra-low phosphorus loading to achieve the superior flame retardancy of epoxy resin

A novel phosphorus-containing compound (DOPO-THPO) is synthesized via the Atherton-Todd-reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and trihydroxymethylphosphine oxide (THPO), and then employed as flame retardant for diglycidyl ether of bisphenol A/4-4 diaminodiphenylmethane epoxy resin (DGEBA/DDM). Based on the ultra-low phosphorus loading, the highly efficient flame retarded epoxy resin (EP) systems are successfully established in this work. Remarkable improvements in the limited oxygen index (LOI) values and UL-94 rating of flame retarded EP systems are observed. In detail, when the phosphorus content is only 0.33 wt%, the EP composite receives V-0 rating in the UL-94 vertical burning test with LOI value of 30%. Heat release of EP composites is obviously inhibited with the formation of intumescent char residue. Furthermore, TG-IR result of DOPO-THPO shows the generation of phosphorus containing products, which may provide a gaseous phase flame retardant function on EP. This work may open the new door for the construction of highly efficient flame retardant EP system based on the ultra-low phosphorus loading.

Synthesis and characterization of the nano alumina-filled tetraglycidyl-4, 4′-diaminodiphenylmethane epoxy resin

In this study, the in situ incorporation of the inorganic alumina nanoparticles into the reactants of tetraglycidyl-4, 4′-diaminodiphenylmethane (TGDDM) epoxy resin represented an efficient way for the preparation of alumina/TGDDM nanocomposite. The surface modification of the alumina nanoparticles was carried out using two individual silane coupling agents, namely, aminopropyltriethoxysilane (APS) and glycidoxypropyltrimethoxysilane (GPS). The degree of silane grafting was evaluated for both coupling agents using FTIR spectroscopy and thermogravimetric analysis. The epoxy equivalent weight (EEW) of the epoxy resin in addition to the weight percentage of the lost nanoparticles during TGDDM polymerization was used as measurements of the polymerization yield. The neat nano alumina has more adverse effect on the epoxy EEW value (171 g/mol) than both silane-modified nano alumina (143–157 g/mol, depending on the reaction conditions). The degree of nano alumina dispersion in the epoxy matrix was investigated using SEM micrographs. The longer and more deflected crack pathways on the fractured surface of the alumina/TGDDM nanocomposites may be attributed to a relatively good degree of dispersion of the silane-modified alumina nanoparticles in the epoxy matrix. Compared to neat alumina, the better dispersion of the silane-modified alumina nanoparticles may be related to the improved interfacial interactions between the oxiran or amine groups available on the silane-modified alumina nanoparticles and the TGDDM epoxy functional groups. Besides, the higher exothermic heat of cure (i.e., 30–53 %) as evidenced in differential scanning calorimetry may be due to a rather good state of dispersion of silane-modified alumina nanoparticles.

An investigation of epoxy/thermoplastic blends based on addition of a novel copoly(aryl ether nitrile) containing phthalazinone and biphenyl moieties

In this paper, a novel soluble copoly(aryl ether nitrile) containing phthalazinone and biphenyl moieties (PPBEN) was synthesized for the first time to improve the impact resistance of tetraglycidyl 4,4'-diaminodiphenylmethane epoxy resin cured with 4,4-diaminodiphenylsulfone. Then a series of blends were prepared via solution blending with different contents of PPBEN. The thermal and mechanical properties and the micromorphology of the cured blends were investigated by differential scanning calorimetry, dynamic mechanical analysis (DMA), parallel plate rheometry, mechanical property tests and SEM analysis, respectively. The results indicated that the incorporation of thermoplastic PPBEN delayed the epoxy curing reaction, and the crosslinking density of epoxies was also reduced. The no-notch impact strength of the cured blend with 15% PPBEN was up to 16.7 kJ m−2, higher by about 104% than that of pure epoxy resin without sacrificing the modulus due to a specific sea-island structure. All the blends showed two-phase morphology characterized by DMA and SEM. The size of the thermoplastic morphology was only 70−80 nm, much less than that of commonly used thermoplastics, due to the special segment structure of PPBEN. © 2015 Society of Chemical Industry

Effect of phosphorus‐containing flame retardants on flame retardancy and thermal stability of tetrafunctional epoxy resin

Hexaphenoxycyclotriphosphazene (HPCTP) and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) were used to flame retard N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane epoxy resins. The curing behaviors and glass transition temperature were investigated by differential scanning calorimetry. The limiting oxygen index (LOI), UL‐94 vertical burning, and cone calorimetry tests were used to assess the flame retardancy of the cured epoxy resins. The increase in LOI value and UL‐94 rating was strongly dependent on the phosphorus content. The reduction in peak of heat release rate and total heat release showed that the incorporation of flame retardants could improve the flame retardancy of epoxy resin. The higher smoke release and CO yield of the flame‐retardant epoxy resins indicated that both DOPO and HPCTP showed a gas phase flame retardancy action. Thermogravimetric analysis of the flame‐retardant epoxy resins indicated that the incorporation of the flame retardants reduced the initial decomposition temperature of epoxy resin. Copyright © 2015 John Wiley & Sons, Ltd.

Cure behaviors and thermal stabilities of tetrafunctional epoxy resin toughened by polyamideimide

The effect of polyamideimide (PAI) content on the cure behaviors and thermal stabilities of 4,4′-tetraglycidyl diaminodiphenyl methane (TGDDM) epoxy resin/polyamideimide (PAI) blends was investigated. The experimental results revealed that the main exothermic peak and cure activation energy (E a ) of the blends decreased with increasing PAI content, presumably because the curing reaction was accelerated by the presence of secondary amine groups of the PAI backbone. The decomposition activation energy (E d ) of the blends was maximized at 5 phr PAI and decreased above this content; this was attributed to the short-chain structural network in TGDDM/PAI blends, which was derived from etherification and chain-scission reactions caused by the secondary amine of PAI.

Synergetic catalytic effect of carbon nanotubes and polyethersulfone on polymerization of glassy epoxy-based systems – isothermal kinetic modelling

The effect of multiwalled carbon nanotubes (MWCNTs) and polyethersulfone (PES) on the polymerization kinetics of N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenyl-methane epoxy resin (TGMDA) and 4,4diaminodiphenyl-methane-methylenebis(2,6-diethylaniline) hardener (MDEA) was studied by means of isothermal differential scanning calorimetry. The autocatalytic (Kamal–Sourour) model was applied to fit the experimental values of epoxy conversion and the total reaction order of 3 with partial orders m and n both equal to 1.5 were found. PES alone did not have any significant effect on epoxy crosslinking kinetics due to its phase separation at the beginning of the epoxy–amine reaction. The presence of MWCNTs substantially increases the epoxy reaction rate but lowers the final epoxy conversion. The important synergetic catalytic effect of MWCNTs and PES on the epoxy kinetics was observed.

Thermal Analysis of a Novel Tetrafunctional Epoxy Resin Cured with Anhydride

The viscoelastic behavior and thermal property of 3, 3'-diethyl-N, N, N', N'-tetraglycidyl-4, 4'-diaminodiphenylmethane (C2H5-TGDDM) epoxy resin in presence of methyl nadic anhydride (MNA) as curing agent and 2-ethyl-4-methyl imidazole (2,4-EMI) as accelerator were investigated by dynamic mechanical thermal analysis (DMTA) in single cantilever mode at different frequencies and non-isothermal DSC-TGA, respectively. According to the DMTA data, the results show that the storage and loss moduli and loss factor curves were shifted to higher temperatures region with increasing frequencies. The value of glass transition temperature (Tg) is in the range of 224 °C to 247 °C, and the difference between the Tg determined by the loss modulus and loss factor peaks is ca. 15 °C, and the glass transition activation energy was calculated. The results of DSC-TGA show that the curing and the decomposition heat-release peaks of epoxy resin were occurred at ca. 191 °C and 360 °C, respectively. The onset temperature of degradation is 324°C, and the epoxy resin system was heat-resistant.

Thermal, electrical and morphological properties of DGEBA/DDM and TGDDM/DDM epoxies modified by a flexible diepoxide and octaphenylamine-POSS

Polyhedral oligomeric silsesquioxane (POSS) nanocrosslinker namely octaaminophenyl silsesquioxane reinforced with 1,1-bis(3-methyl-4-glycidyloxyphenyl)cyclohexane (diepoxide) modified diglycidyl ether of bisphenol-A (DGEBA) and tetraglycidyl diamino diphenyl methane (TGDDM) epoxy resins and cured with 4,4′-diaminodiphenylmethane (DDM). The chemical reactions that occurred between epoxy resins and DDM with POSS were confirmed by Fourier transform infrared spectroscopy. POSS-reinforced hybrid diepoxide-epoxy resin nanocomposites were characterised for their thermal, electrical and morphological properties. Tg and heat distortion temperature of hybrid epoxy increases with increased incorporation of POSS. The data obtained from thermal studies indicated that the incorporation of nano-POSS into diepoxide-modified hybrid systems possess improved thermal stability. Dielectric properties decreased with increasing percentage of POSS in both systems. The nanolevel dispersion of octaaminophenyl silsesquioxane (POSS) was confirmed by X-ray diffraction analysis and transmission electron microscope studies.

Studies on synthesis and characterization of hydroxyl-terminated polydimethylsiloxane-modified epoxy bismaleimide matrices

This work reports the development of hydroxyl-terminated polydimethylsiloxane (HTPDMS)-toughened tetraglycidyl diaminodiphenyl methane (TGDDM) epoxy matrix systems. The siliconized epoxy systems were further modified with various percentages of (5, 10 and 15 wt%) 10-phenyl-phenonoxaphosphine-3,8-di(2-hydroxy-3-( p-male-imidobenzoyloxy)propyl) ester-10-oxide (EPBMI) and cured by diaminodiphenyl sulfone. Thermal, mechanical and morphological properties of the prepared samples were studied by standard methods. In comparison with the unmodified epoxy resin, HTPDMS-incorporated TGDDM resin showed increased impact strength with a reduction in tensile strength, flexural strength and glass transition temperature ( Tg). But in the case of bismaleimide (BMI; EPBMI)-incorporated epoxy resin, tensile strength, flexural strength and Tg showed an increasing trend. However, the introduction of both siloxane and BMI into epoxy influences the mechanical and thermal properties according to their percentage content. The morphology of the silconized and the BMI-modified epoxy systems was also studied by scanning electron microscopy.

Preparation and Characterization of Cyclohexyl Moiety Toughened POSS-Reinforced Epoxy Nanocomposites

Polyhedral oligomeric silsesquioxane (POSS)-reinforced epoxy nanocomposites were prepared by reacting commercially available diglycidyl ether of bisphenol-A (DGEBA) and tetraglycidyl diamino diphenyl methane (TGDDM) epoxy resins with 1,1-bis(3-methyl-4-glycidyloxyphenyl)cyclohexane (Cy-Ep) separately and reinforced with POSS nanocluster. POSS (OAPS)-reinforced hybrid Cy-Ep-epoxy resin castings were characterized for their mechanical and morphological properties. The data obtained from mechanical studies indicated that the incorporation of nano OAPS into Cy-Ep modified hybrid systems results in improved stability. Among the epoxy systems studied, the TGDDM-based hybrid epoxy system exhibited higher values of tensile and flexural properties than that of the DGEBA hybrid epoxy system, whereas the impact strength of the DGEBA system was higher than that of the TGDDM system. The dispersion of POSS was confirmed by scanning electron microscopy and visual observation studies.

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.