Tetraglycidyl Diaminodiphenyl Research Articles

Constructing and characterizing various multi-component crosslinked epoxy resins based on molecular dynamics simulations with a curing reaction model

Epoxy resins are extensively used as the matrix for carbon-fiber-reinforced plastic (CFRP) in commercial airplanes due to their outstanding thermomechanical properties. Until now, few researchers have simulated multicomponent epoxy resins. In this work, the impact of stoichiometric variations in the base resins in the Di Glycidyl Ether of Bisphenol A (DGEBA)/Tetra Glycidyl Diamino Diphenyl Methane (TGDDM)/4,4′-Diamino Diphenyl Sulfone (4,4′-DDS) system on the curing process and thermomechanical properties is investigated. When the proportions of each component are comparable, the curing process is primarily determined initially by the component with a lower activation energy and subsequently by the component with a relatively greater quantity during the high conversion rate stage. Furthermore, a higher proportion of TGDDM in the DGEBA/TGDDM/4,4′-DDS system results in an increased number of ring structures, which in turn leads to enhanced thermomechanical properties. Our Python-LAMMPS algorithm can be further developed for designing new multi-component epoxy resin materials.

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.

Fracture behavior of high‐performance carbon fiber composites toughened by reactive polyetherimide

AbstractCarbon fiber‐reinforced epoxy composites (CFECs) continue to grow in demand for aerospace, mass transportation, electric vehicle, and energy efficient architecture due to their lightweight, high strength, and high modulus. However, CFECs are susceptible to delamination upon impact which can lead to premature structural failure. This paper investigates the interlaminar fracture toughness of unidirectional CFECs based on reactive polyetherimide (rPEI) modified multifunctional epoxy matrix system. The matrices were cured formulations of tetraglycidyl diamino diphenyl methane, triglycidyl para‐amino phenol, rPEI having different molecular weights (MW) and diaminodiphenyl sulfone. Multi‐phase morphologies were observed from the resin castings and CFECs containing different MW rPEI modifiers. Results show that the mode I fracture toughness (GIC) of the rPEI‐toughened CFECs can be increased by as much as 150% over the unmodified CFECs based on the MW and type of phase morphology that promotes crack‐bridging mechanism. In addition, rPEI‐modified CFECs exhibit better property retention (~80% of GIC) after prolonged solvent exposure.Highlights A processing‐structure–property relationship based on CFECs is established. The amine‐terminated rPEI facilitates the formation of a strong bonding. The molecular weight effect of rPEI on the phase morphology was investigated. The rPEI enhances the interlaminar fracture toughness of the composites. The rPEI particle bridging is found to be responsible for the toughening effect.

Molecular-scale investigation on relationship between thermal conductivity and the structure of crosslinked epoxy resin

Epoxy resins are widely used as matrix resins in many fields due to their excellent physical and mechanical properties. However, their low thermal conductivities restrict their applications, especially in electronic packaging. In this work, nonequilibrium molecular dynamics (NEMD) simulations were used to investigate the relationship between thermal conductivity and epoxy resin structure. Three systems, diglycidyl ether of bisphenol A (DGEBA)/4,4’-diamino diphenyl sulfone (4,4’-DDS), DGEBA/diethylene triamine (DETA), and tetraglycidyl diamino diphenyl methane (TGDDM)/4,4’-DDS, were simulated based on our previous crosslinking algorithm. The thermal conductivity of DGEBA/4,4’-DDS increased with the degree of crosslinking, which is due to increases in new thermal pathways through crosslinking bonds. The sequence of thermal conductivities was found to be TGDDM/4,4’-DDS > DGEBA/DETA > DGEBA/4,4’-DDS which was quantitatively validated with our experimental measurements, consistent with the sequence of crosslink density. To explore the microscopic mechanism governing thermal conductivity, separate heat transfer modes were investigated, revealing that the thermal conductivity contribution of bonded interactions dominates over that of non-bonded interactions for all three systems. This finding verifies that introducing crosslinking bonds dominantly contributes to higher thermal conductivity in epoxy materials. Our research provides suggestions for large scale manufacture of higher thermal conductive epoxy resins.

Internal topology and water transport in tetrafunctional epoxy resins

AbstractWater sorption into epoxy resins limits the performance lifetime of many composites, adhesives, and coatings. One hypothesis for the well‐known hygroscopicity of epoxies is that the well‐known internal nodular topology of epoxy networks enhances permeability. This theory has however remained untested to date, since previous attempts to manipulate the internal topology have been accompanied by changes in the hydrogen bonding capability of resins, which dominates water uptake. Here, the nanostructure of highly cross‐linked network polymers based on tetra glycidyl diaminodiphenyl methane is varied in the absence of significant polarity effects by careful optimization of the cure schedule. The internal morphology of resins cured at 100, 150, and 200°C are characterized using Peakforce tapping mode atomic force microscopy, whilst the cure progression at each temperature is analyzed using in‐situ transmission mode infrared spectroscopy. Distinct nodular morphologies are found to form at high cure temperatures (150 and 200°C), where spectroscopic analysis demonstrates that excess epoxy consumption occurs prior to the gel point, as a result of intra‐cluster cross‐linking and reduced reaction selectivity. Surprisingly, the establishment of an internal nanostructure is, however, found to have negligible effect on the extent and kinetics of moisture sorption.

Preparation Characterization of Modified Poly(Lactic Acid) Using Dicumyl Peroxide and Tetraglycidyl Diamino Diphenyl Methane

Poly(lactic acid) (PLA) was modified using dicumyl peroxide (DCP) and tetraglycidyl diamino diphenyl methane (TGDDM) to improve its melt viscosity and molecular weight for a variety of industrial applications. The PLA was branched or crosslinked with DCP at 180 °C, and gel content was detected as the DCP concentration was over 0.6 phr. However, for TGDDM, it was observed that only chain extension or branching occurred; the number- and weight-average molecular weights and polydispersity index (PDI) increased. The melt flow index decreased as the concentration levels of DCP and TGDDM increased. However, when the TGDDM was over 0.5 phr, the opposite results were observed. The variations in the mechanical properties of modified PLA were marginal; however, the elongation at break slightly decreased. The onset value of the decomposition temperature of the DCP-modified PLA slightly decreased. In contrast, with TGDDM, the onset value slightly increased. As the branching and crosslinking of the modified PLA increasingly occurred, relatively low relaxation enthalpy was detected. However, the glass transition temperature (Tg) was not influenced. An increase in the storage modulus (G′), loss modulus (G″), and complex viscosity (η*), and a decrease in tan δ at low frequencies showed that the rheological behavior of the modified PLA turned from liquid-like to solid-like because of the modifications achieved using DCP and TGDDM.

Study of the acoustic emission response to a core-shell rubber-toughened, high-temperature composite

This work explores the effect of core-shell rubber (CSR) addition on the cure reaction and resulting mechanical and thermal properties of a highly cross-linked network made from 4,4′- tetraglycidyl diamino diphenyl methane and 3,3′-diamino diphenyl sulphone. Up to 20 wt% of a CSR rubber, composed of a soft polybutadiene core and a hard poly methyl methacrylate (PMMA) shell was dispersed in the epoxy/amine and after cure was found to increase the glass transition temperature and thermal degradation temperatures modestly, while reducing the char yield. Flexural properties also reduced with CSR addition, although fracture toughness (KIC) was increased by 45% at 20 wt% of CSR. Furthermore, the fracture strain energy release rate (GIC) of the corresponding carbon fibre composite at the same CSR concentration, increased by almost 115%. Acoustic emission spectroscopy is introduced as a tool for investigating crack propagation during mode I loading and identifying any differences in the failure mechanism between the unmodified and the 20 wt% CSR-modified carbon fibre composites.

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).

Analysis of high melt‐strength poly(ethylene terephthalate) produced by reactive processing by shear and elongational rheology

Three grades of poly(ethylene terephthalate) (PET) produced by different synthesis routes and with different molar masses were reactively extruded with two tetra‐functional chain extenders, i.e., pyromellitic dianhydride (PMDA) and tetraglycidyl diamino diphenyl methane (TGDDM). The preferred reactivity of the coupling agents led to different long‐chain branched (LCB) structures, which can be related to different hydroxyl and carboxyl end group concentrations of the PET grades investigated. The complex viscosity and the transient elongational viscosity increased by up to two decades. Both the activation energy of flow and the loss angle indicate long‐chain branching. A more quantitative assessment of the extent of strain hardening was achieved by application of the molecular stress function (MSF) model. The two material parameters of the model revealed different behaviors depending on the chain extender used. The initial molar mass of PET and the concentration of end groups, i.e., hydroxyl and carboxyl, determine the structure of the polymer molecules. PMDA proved to be an excellent coupling agent for industrial processing which induces reproducibly either a star‐like, comb‐like, or randomly branched structure depending on the concentration of coupling agent added and the hydroxyl concentration of the PET employed. TGDDM led to a hyperbranched structure. POLYM. ENG. SCI., 59:396–410, 2019. © 2018 Society of Plastics Engineers

The mechanical behaviors of epoxy-terminated hyperbranched polyester (E-HBP) as toughener in different epoxy resins

Using epoxy-terminated hyperbranched polymer (E-HBP) to modify epoxy resin (EP) is an effective way to improve the toughness of EP. In the present study, two different epoxy resin systems with E-HBP are researched: a commercial diglycidyl ether bisphenol A (DGEBA) resin with anhydride as curing agent and a tetraglycidyl diaminodiphenyl methane (TGDDM) resin with diamine as curing agent. Characterization results show that the addition of E-HBP could improve the mechanical properties of the two epoxy resin systems, such as tensile strength, elongation, and modulus of elasticity. Meanwhile, the glass transition temperature (T g ) of the two systems does not decrease. However, the morphology of the tensile fracture surfaces of the two modified systems shows different behaviors. Significant plastic deformation could be observed in the fracture surfaces of the modified DGEBA/anhydride system, and particle cavitations are clearly shown in the fracture surfaces of the modified TGDDM/diamine systems. The analysis of the tensile fracture surfaces suggests that firstly E-HBP participates in the curing process of the modified resin systems, followed by the chemical-induced phase separation; finally, a gradient transition interface layer (GTIL) is formed. Apart from these, during the external loading process, the mechanical behaviors (deformation or cavitation) of the separated E-HBP particles in the modified epoxy resins are affected by the properties of the epoxy matrix itself.

Rheological and molecular characterization of long-chain branched poly(ethylene terephthalate)

Reactive extrusion with pyromellitic dianhydride (PMDA) and tetraglycidyl diamino diphenyl methane (TGDDM) was conducted to create long-chain branched poly(ethylene terephthalate) (LCB-PET). The mechanical and molecular properties were analyzed by linear and non-linear viscoelastic rheology in the melt state and by size-exclusion chromatography measurements with triple detection. The two tetra-functional chain extenders lead to strong viscosity increases, increasing strain hardening effects, and increasing LCB with increasing chain extender concentration. Molecular stress function model predictions show good agreement with the elongational data measured and allowed a quantification of the strain hardening. Analysis of SEC triple detection data shows a strong increase of the average molar mass, polydispersity, radius of gyration, and hydrodynamic radius with increasing chain extender concentration. Branching was confirmed by a decreasing Mark-Houwink exponent, and the analysis of the contraction of the molecule revealed either star-like, comb-like, random tree-like or hyperbranched structures depending on concentration and type of chain extender.

An efficient healing agent for high temperature epoxy composites based upon tetra-glycidyl diamino diphenyl methane

Poly(ethylene-co-methacrylic acid) (EMAA) as a thermally activated healing agent in a high performance, high temperature tetra-glycidyl methylene dianiline (TGDDM)/diethyl toluene diamine (DETDA) mendable epoxy composite is reported for the first time. Despite curing above EMAAs melting point (Tm=85°C), healing occurred by incorporating a preliminary low temperature curing step of 5h at 80°C, prior to cure at 177°C. Healing occurred via the pressure delivery mechanism derived from tertiary amine catalysed surface condensation reactions between EMAA and hydroxyl groups from the epoxy resin. Healing efficiencies of 36%, 55% and 105% were achieved after heating at 150°C, 200°C and 230°C respectively, but decreased rapidly with continued healing. Healing at 150°C and 200°C revealed significant healing despite remaining in the glassy state. In addition, EMAA enhanced mode I interlaminar fracture toughness by more than 270% for both the DETDA and 4,4-DDS networks.

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.

Reactive Modification of Poly(ethylene terephthalate) and its Foaming Behavior

A methodology for the preparation of chain extended poly (ethylene terephthalate) (PET) and its foams by autoclave batching foaming method was proposed. First, PET was mixed with tetraglycidyl diamino diphenyl methane (TGDDM) as chain extender to generate the branching/crosslinking molecular structure and improve the viscoelasticity of PET. Then, PET foams were prepared using supercritical CO2 as physical blowing agent. The molecular structures of various PET samples were characterized by the nuclear magnetic resonance, gelation degree and crosslinking density test. The results showed that with the introduction of TGDDM, the branching/crosslinking structure of PET appeared. The influences of various molecular structures on the thermal property and rheology of PET were also studied. The results showed that the crystallization temperature, crystallization rate, and crystallinity of various PET samples decreased with the content of TGDDM, but the modified PET had higher melt elasticity than that of pure PET. PET foam with the addition of 0.4% TGDDM had finer cellular morphology and the highest expansion ratio.

Study on flame retardancy of TGDDM epoxy resins loaded with DOPO-POSS compound and OPS/DOPO mixture

The DOPO-POSS (polyhedral oligomeric silsesquioxane containing DOPO) and OPS/DOPO (octaphenyl polyhedral oligomeric silsesquioxane/DOPO) are used to flame retard the TGDDM/DDS (tetraglycidyl diamino diphenyl methane/4,4′-diaminodiphenylsulphone) resins. The blowing-out effect can be detected during the UL-94 tests of them. The LOI and UL-94 results indicate that DOPO-POSS or OPS/DOPO could make the LOI values of TGDDM/DDS resins greater than 34% and the UL-94 test reach V-0 rating. When keeping the same content of Si and P elements in the epoxy resins, the OPS/DOPO shows better flame retardancy and make the epoxy resins have better blowing-out intensity. The condensed phase and the gas products of TGDDM/DDS resins with DOPO-POSS and OPS/DOPO are investigated by the TGA, TGA–FTIR, SEM, FTIR and XPS. In the gas phase, DOPO-POSS and OPS/DOPO have negligible action on the gaseous product species of TGDDM/DDS resins. However, in the condensed phase, quite different performance of DOPO-POSS and OPS/DOPO can be observed. The good flame retardancy of the OPS/DOPO on the TGDDM/DDS resins is attributed to the matching between the melt viscosity and fast swelling, accumulation of the pyrolytic gases in the condensed phase, and fast and firm charring. Furthermore, the superabundant C–O-R structure in the condensed phase may be origin of the melt viscosity matching with melt swelling, and firm char during combustion.

Effect of epoxy resin properties on the mechanical properties of carbon fiber/epoxy resin composites

Abstract Three kinds of epoxy resins, i.e. tetraglycidyl diaminodiphenyl methane (AG80), difunctional diglycidyl ether of bisphenol-A (E51) and novolac type epoxy resin (F46) were selected as matrices for carbon fiber/epoxy composites. The objective of this work is to study the mechanical properties of fiber/epoxy composites by using these three kinds of epoxy resins with different physical and chemical performance. The results show that the composites fabricated with AG80 present the best stiffness and the composites prepared with E51 have the best toughness. The stiffness and toughness of the composites prepared with F46 are middle values located between those for AG80/epoxy and E51/epoxy composites. Thus, the mixed epoxy resin is a promising approach for industrial production.

Fluorine Mobility During SEM-EDX Analysis: A Challenge for Characterizing Epoxy/Fluoropolymer Interfaces

Precisely characterizing epoxy/thermoplastic interfaces on the nanometer scale using scanning electron microscopy energy-dispersive X-ray (EDX) represents a current challenge due to the large X-rays generation volume, specimen decomposition, and related phenomena occurring with polymer samples. Interface characterization is, however, of high interest because the adhesion strength and overall performance of composites depend on the interface region. This work investigates the interface between an aerospace-grade epoxy based on a tetraglycidyl diaminodiphenyl methane/diaminodiphenyl sulphone (TGDDM/DDS) formulation and a semicrystalline fluoropolymer. Monte Carlo simulation is used in combination with EDX spot analysis to evaluate the effect of X-ray generation volume, charging, and phenomena arising from specimen decomposition. The results indicate that fluorine mobility due to specimen damage by electron beam irradiation is the principal factor affecting interface width measurements. An effective solution...

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.