Diglycidyl Ether Of bisphenol-A Epoxy Resin Research Articles

Study of the Curing Process of DGEBA Epoxy Resin Through Structural Investigation

In this work, a multi‐scale approach with different analytical methods is applied to study the curing process and the structural properties of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin. This monomer, thermally cured using 4,4′‐diaminodiphenilsulfone (DDS) as hardener, is analyzed after 10, 45, 90, and 120 min of reaction time at 180 °C to obtain information on samples with different cross‐linking densities. Samples are also characterized after extraction in acetone in order to obtain structural information on the insoluble parts. For this purpose, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), solid‐state nuclear magnetic resonance (ss‐NMR), and positron annihilation lifetime spectroscopy (PALS) are employed. The importance of this multi‐method approach lies in the possibility to obtain a more complete knowledge of the investigated system, overcoming the limits inherent to the use of a single technique, through the correlation among results obtained from different structural investigation methodologies. image

Chemical degradation of amine-cured DGEBA epoxy resin in supercritical 1-propanol for recycling carbon fiber from composites

Chemical degradation of diglycidyl ether of bisphenol A (DGEBA) epoxy resin cured with an aliphatic amine in supercritical 1-propanol was investigated under different reaction temperature and time. The combination of GC-MS and LC-MS proved that the epoxy resin was decomposed to five main products including phenol, 4-isopropylphenol, 4-isopropenylphenol, bisphenol A, and 4,4'-(cyclopropane-1,1-diyl)diphenol. The 13 C-NMR results verified the chemical structures of the degradation products. The change of the productsyield with time was evaluated by an effective means of HPLC. In addition, the GPC analysis confirmed the formation of soluble low molecular weight clusters during the degradation reaction. A possible free-radical reaction mechanism was proposed for chemical depolymerization of the epoxy resin in supercritical 1-propanol. After the homolytic cleavage of the aromatic ether linkages, the resulting bisphenol A biradical either produced 4,4'-(cyclopropane-1,1-diyl)diphenol after intramolecular rearrangement or generated bisphenol A after capturing hydrogen from 1-propanol.

Preparation and characterization of epoxy–silica networks chemically bonded through aminophenyl-trimethoxysilane

Epoxy–silica hybrids with interfacial bonding using aminophenyl-trimethoxysilane (APTMOS) have been prepared by the sol–gel process. In a sequential polymerization procedure the amine groups present on the APTMOS were used to partially cure diglycidyl ether of bisphenol-A (DGEBA) whereas the methoxy groups created silica-network simultaneously, through the sol–gel process. Complete curing and cross-linking were carried out later using curing agent jeffamine D-400 at higher temperature. The nature of silica network structure chemically bonded with the epoxy chains was studied by Fourier transformed infrared spectroscopy and the morphology of the hybrid through scattering electron and atomic force microscopies. The visco-elastic properties of the resulting hybrids were measured through dynamical thermal mechanical analysis. The effect of inter-phase bonding of the resulting hybrids and their thermal mechanical properties are compared with the similar DGEBA epoxy matrix where un-bonded silica network was produced from tetraethoxysilane. The properties of the hybrids using APTMOS show considerable improvement in thermal mechanical properties and the coefficient of thermal expansion is reduced in contrast to the un-compatiblized system.

Recycling of carbon fibers inserted in composite of DGEBA epoxy matrix by thermal degradation

In this study, carbon fibers inserted into an epoxy resin derived from diglycidyl ether of bisphenol-A (DGEBA) were recovered based on the complete removal of the matrix by thermal treatment. The degradation of the composite was carried out at various experimental conditions and the ideal one was obtained at 450 °C for 2 h. Under this condition, all of the resin was removed without degrading the C fibers to any significant degree. The results of thermogravimetric analysis revealed several stages of thermal decomposition depending on the material analyzed. It was established by thermogravimetry analyses that the epoxy matrix starts to experience intense degradation at temperatures above 280 °C with maximum loss in the temperature range of 360–410 °C. In the case of composite samples above 800 °C a residue of approximately 50% by weight can be observed, which is related to carbon fibers. Confirmation of the removal of the resin from the carbon fiber was obtained by means of scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The kinetic of release of CH4, CO2 and N2O gases during degradation process was accompanied by gas chromatography. The concentrations of methane and carbon dioxide increased significantly during the first 10 min of the processing and after this, no released quantities were verified. On the other hand N2O continues to be released even after 3 h of the process of burning the composite in air atmosphere. The treatment proposed in this study can be considered to be a low-cost one as well as being interesting for the recovery of C fibers present in DGEBA matrix which would normally be discarded after use.

Crystallization in PHB/DGEBA blends

ABSTRACTReal‐time experiments using small‐angle X‐ray scattering and differential scanning calorimetry on blends of the semicrystalline polyester poly(3‐hydroxybutyrate) (PHB) and amorphous monomer epoxy DGEBA (diglycidyl ether of bisphenol A) were performed. Differences in the processes of melting and re‐crystallization were observed in blends relative to pure PHB. The results obtained in this study indicated that re‐crystallization is more important in blends with 50% DGEBA than in pure PHB. Moreover, segregation toward the interfibrillar region would facilitate re‐crystallization. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 882–886

Proton conductive membranes based on poly(styrene-co-allyl alcohol) Semi-IPN

The optimization of fuel cell materials, particularly polymer membranes, for PEMFC has driven the development of methods and alternatives to achieve systems with more adequate properties to this application. The sulfonation of poly (styrene-co-allyl alcohol) (PSAA), using sulfonating agent:styrene ratios of 2:1, 1:1, 1:2, 1:4, 1:6, 1:8 and 1:10, was previously performed to obtain proton conductive polymer membranes. Most of those membranes exhibited solubility in water with increasing temperature and showed conductivity of approximately 10-5 S cm-1. In order to optimize the PSAA properties, especially decreasing its solubility, semi-IPN (SIPN) membranes are proposed in the present study. These membranes were obtained from the diglycidyl ether of bisphenol A (DGEBA), curing reactions in presence of DDS (4,4-diaminodiphenyl sulfone) and PSAA. Different DGEBA/PSAA weight ratios were employed, varying the PSAA concentration between 9 and 50% and keeping the mass ratio of DGEBA:DDS as 1:1. The samples were characterized by FTIR and by electrochemical impedance spectroscopy. Unperturbed bands of PSAA were observed in the FTIR spectra of membranes, suggesting that chemical integrity of the polymer is maintained during the synthesis. In particular, bands involving C-C stretching (1450 cm-1), C=C (aromatic, ~ 3030 cm-1) and C-H (2818 and 2928 cm-1) were observed, unchanged after the synthesis. The disappearance or reduction of the intensity of the band at 916 cm-1, attributed to the DGEBA epoxy ring, is evidenced for all samples, indicating the epoxy ring opening and the DGEBA crosslinking. Conductivity of H3PO4 doped membranes increases with temperature, reaching 10-4 S cm-1.

Effect of Electric Frequency on the Partial Discharge Resistance of Epoxy Systems with Two Diluents

Partial discharge resistance for the epoxy systems with two diluents was investigated in the rod-plane electrodes arrangement, and the effect of electric frequency on the partial discharge resistance was also studied. Diglycidyl ether of bisphenol A (DGEBA) type epoxy was used as a base resin, and 1,4-butanediol diglycidyl ether (BDGE) or polyglycol (PG) as a reactive diluent was introduced to the DGEBA system, in order to decrease the viscosity of the DGEBA epoxy system. BDGE was acted as a chain extender, and PG acted as a flexibilizer, after the curing reaction. To measure the partial discharge resistance, 5 kV alternating current (ac) with three different frequencies (60, 500 and 1,000 Hz) was applied to the specimen in a rod-plane electrode arrangement, at <TEX>$30^{\circ}C$</TEX>. PG had a good effect, while BDGE had a bad effect on the partial discharge resistance of the DGEBA system, regardless of the electric frequency.

Impact of aliphatic amine comonomers on DGEBA epoxy network properties

This study characterized the mechanical and thermal properties of the oligomer‐based formulations of the diglycidyl ether of bisphenol A (DGEBA) cured with series aliphatic amines (triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and O,O bis (2‐aminopropyl propylene glycol) (Jeffamine D230) with different functionalities in the glassy state. Impact Izod and three‐point bending tests were conducted to determine the networks' impact energy (Ei), elasticity modulus (Ey), yield stress (σy) and fracture toughness (KIC) values. The same three‐point bending mode was also employed to characterize the systems' thermo‐mechanical properties (DMA) and storage modulus (E') and damping modulus (tan δ = E"/E') values. The DGEBA/D230 network showed greater flexibility, maximum impact energy, higher fracture toughness, and a lower yield stress than the DGEBA/TETA and DGEBA/TEPA networks. The fracture behavior of these epoxy systems was correlated to the molecular weight between the crosslink points, Mc, and the plastic zone size (rp) at the crack tip carved in the samples. The DGEBA/D230 network had the highest storage modulus and tan δ intensity, together with higher toughness and deformation during the network's fracture. These results were a consequence of the structural characteristics of comonomers, including their chain segment flexibility, molecular weight between crosslink points and functionality. POLYM. ENG. SCI., 54:2132–2138, 2014. © 2013 Society of Plastics Engineers

Experimental studies of the deformation mechanisms of core-shell rubber-modified diglycidyl ether of bisphenol-A epoxy at cryogenic temperatures

Epoxy polymers, although often used in fiber-reinforced polymeric composites, have an inherent low toughness that further decreases with decreasing temperatures. Second-phase additives have been effective in increasing the toughness of epoxies at room temperature; however, the mechanisms at low temperatures are still not understood. In this study, the deformation mechanisms of a diglycidyl ether of bisphenol-A epoxy modified with MX960 core-shell rubber particles were investigated under quasi-static tensile and impact loads at room temperature and liquid nitrogen temperature. Overall, the core-shell rubber had little effect on the tensile properties at room temperature and liquid nitrogen temperature. The impact strength decreased from neat to 1 wt% and 3 wt% but increased from neat to 5 wt% at room temperature and liquid nitrogen temperature, with a higher impact strength at room temperature at all core-shell rubber loadings. While a large toughening effect was not seen in this study, the mechanisms analyzed herein will likely be of use for further material investigations at cryogenic temperatures.

Hyperbranched polysiloxane‐based diglycidyl ether of bisphenol a epoxy composite for low k dielectric application

A new type of diglycidyl ether of bisphenol A (DGEBA) epoxy‐based hybrids has been developed by the incorporation of varying percentages of glycidyl‐terminated hyperbranched polysiloxane (HPSiE) into DGEBA resin and are characterized for their physicochemical, thermal, mechanical, and dielectric behaviors by modern analytical techniques. Data resulted from different studies indicate that the incorporation of HPSiE into DGEBA epoxy resin significantly improved the impact strength, thermal, and dielectric properties with an increase in the HPSiE loading. The contact angle [water and diiodomethane (DI)] increase with increases according to the weight percentages of HPSiE, which indicates the HPSiE‐modified DGEBA shows hydrophobic in nature. The resulting epoxy‐based hybrid composites can be used effectively for different industrial and engineering applications for better performance with improved longevity. POLYM. COMPOS., 34:904–911, 2013. © 2013 Society of Plastics Engineers

AFM and XRD characterization of silver nanoparticles films deposited on the surface of DGEBA epoxy resin by ion sputtering

In this work, silver atoms were deposited by ion sputtering on the surface of diglycidyl ether of bisphenol A (DGEBA) epoxy resin cured at 150 °C for 6 hours in air. The films of DGEBA and its precursors were characterized by Raman spectroscopy to identify the main functional groups and their relationship with the deposited silver atoms. Silver thin films of 5, 10, 15 and 20 nm were deposited on the epoxy resin at room temperature. Both the initial film of DGEBA and the subsequent silver thin film were analyzed by Atomic Force Microscopy (AFM) in the non-contact mode. Silver thin films were also analyzed using X-ray diffraction (XRD) at room temperature. The AFM results showed the formation of silver crystallites on the surface of DGEBA at very low coverage whereas XRD indicated that most of them had their main axis aligned to the normal of the surface. An increase in the coverage led to an increase in the grain size as indicated by AFM. However, XRD results indicated that the crystallite size remained almost constant while the appearance of peaks corresponding to other crystalline orientations suggests the coalescence of the original crystallites and an increase in size of the more dense planes, namely [111].

Miscibility in crystalline/amorphous blends of poly(3‐hydroxybutyrate)/DGEBA

AbstractA differential scanning calorimetry (DSC) and small‐angle X‐ray scattering (SAXS) study of miscibility in blends of the semicrystalline polyester poly(3‐hydroxybutyrate) (PHB) and amorphous monomer epoxy DGEBA (diglycidyl ether of bisphenol A) was performed. Evidence of the miscibility of PHB/DGEBA in the molten state was found from a DSC study of the dependence of glass transition temperature (Tg) as a function of the blend composition and isothermal crystallization, analyzing the melting point (Tm) as a function of blend composition. A negative value of Flory–Huggins interaction parameter χPD was obtained. Furthermore, the lamellar crystallinity in the blend was studied by SAXS as a function of the PHB content. Evidence of the segregation of the amorphous material out of the lamellar structure was obtained. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013

Curing Reaction Kinetics of Epoxy/MWCNT-P Composites

The effects of the functionalized multi-walled carbon nanotubes (MWCNT-P) on the curing behavior of a diglycidyl ether of bisphenol-A epoxy (DGEBA) in the presence of 4,4'-methylenedianiline were investigated by non-isothermal differential scanning calorimetry. Activation energy (Ea) was obtained through Kissinger and Ozawa methodsItalic text respectively, and reaction order(n) was educed by Crane equation. The results showed that the addition of MWCNT-P enhanced the cure reaction of DGEBA with 4,4'-methylenedianiline, compared with pure epoxy system, epoxy containing MWCNT-P exhibited a lower activation energy. Both systems presented the same reaction orders, which indicated MWCNT-P did not change the auto-catalytic cure reaction mechanism of the epoxy resin.

Curing of DGEBA epoxy using a phenol-terminated hyperbranched curing agent: Cure kinetics, gelation, and the TTT cure diagram

The cure of diglycidyl ether of bisphenol A (DGEBA) epoxy with a novel phenol-terminated hyperbranched curing agent in stoichiometric ratio was studied comprehensively. The cure behavior was investigated using differential scanning calorimetry (DSC) in both isothermal and dynamic modes. The gelation times were determined by thermal mechanical analysis (TMA). Ramp cure data were analyzed by means of the Vyazovkin's model free method. The isothermal cure data were analyzed using the Kamal model and the time–temperature-superposition (TTS) kinetic method. In spite of a high ultimate conversion, onset of diffusion control sets in well before vitrification. The effects of diffusion were incorporated into the overall kinetics expression using a diffusion factor. The gel conversion is found to be independent of cure temperature, and an effort has been made to compare the measured gel conversion with the theoretical prediction. In addition, the isothermal time–temperature-transformation (TTT) cure diagram was reported.

Synthesis of a hyperbranched polyether epoxy through one-step proton transfer polymerization and its application as a toughener for epoxy resin DGEBA

A novel liquid hyperbranched polyether epoxy (HBPEE) based on commercially available hydroquinone (HQ) and 1,1,1-trihydroxymethylpropane triglycidyl ether (TMPGE) was synthesized through an A2 + B3 one-step proton transfer polymerization. In order to improve the toughness, the synthesized HBPEE was mixed with diglycidyl ether of bisphenol A (DGEBA) in different ratios to form hybrids and cured with triethylenetetramine (TETA). Thermal and mechanical properties of the cured hybrids were evaluated. Results show that addition of HBPEE can improve the toughness of cured hybrids remarkably at < 20 wt% loading, without compromising the tensile strength. However, the glass transition temperature (T g) of the cured hybrids decreases with increasing HBPEE content. Fracture surface images from scanning electron microscope show oriented fibrils in hybrids containing HBPEE. The formation and orientation of the fibrils can absorb energy under impact and lead to an improvement of toughness. Furthermore, based on the morphology of fractured surfaces and the single T g in each hybrid, no sign of phase separation was found in the cured hybrid systems. As a result, the toughening mechanism could be explained by in situ homogeneous toughening mechanism rather than phase separation mechanism.

Blowing-out effect in epoxy composites flame retarded by DOPO-POSS and its correlation with amide curing agents

A novel polyhedral oligomeric silsesquioxane containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-POSS) has been used to flame retard DGEBA (diglycidyl ether of bisphenol A) epoxy resins cured by two amides, namely the aliphatic oligomeric polyamide 650 (PA650) and the aromatic 4,4′-diaminodiphenylsulphone (DDS). The epoxy composites with DOPO-POSS showed different flame retardant properties depending on the amide used. The results of UL-94 tests show that the DEGBA/DDS with DOPO-POSS exhibits a blowing-out effect through vigorous emission of pyrolytic gases, but the DEGBA/PA650 does not. Moreover, only 2.5 wt.% DOPO-POSS imparts to the epoxy resin DEGBA/DDS a LOI value of 27.1% and UL-94 V-1 rating. In contrast, 10 wt.% DOPO-POSS in the DEGBA/PA650 results in a LOI value of 25.9% and a UL-94 V-1 rating. The details of fire behaviour, such as the values of TTI, HRR, p-HRR, COPR, and CO2PR have been tested using a cone calorimeter. DOPO-POSS in the DEGBA/DDS causes a lower value of p-HRR and longer TTI than in the DEGBA/PA650. The DEGBA/DDS with even as little as 2.5 wt.% DOPO-POSS easily forms a compact char. However, the DEGBA/PA650 with DOPO-POSS does not char until 10 wt.% DOPO-POSS has been added. The thermal stability and pyrolytic gases of the two kinds of epoxy resins were assessed by TGA-FTIR under a nitrogen atmosphere. DOPO-POSS performs better in accelerating charring in the DDS curing system compared with the PA650 curing system. It is postulated that for the DEGBA/DDS/DOPO-POSS, fast and dense charring and accumulating of pyrolytic gases in the char contribute to the blowing-out effect. By contrast, the aliphatic chain of the PA650 is easy to break down and produce combustible gases, so does not easily form a crosslinked structure in the condensed phase until enough DOPO-POSS has been added. These results may be very helpful for investigation of the conditions under which the blowing-out effect in epoxy resins can be caused by synergy of phosphorous (DOPO) and silicon (POSS).

Disecondary amine synthesis and its reaction kinetics with epoxy prepolymers

Abstract3,3′‐Diaminodiphenyl sulfone (3,3′‐DDS) was reacted with acetaldehyde in the presence of sodium triacetoxy borohydride via reductive amination to yield a 3,3′‐DDS based secondary diamine, N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone. Near IR analysis indicated that the 5060 cm−1 peak for primary amine (NH2) in 3,3′‐DDS was absent in the reaction product spectrum. The NH2 proton peak at δ 5.66 ppm shifted to δ 6.16 ppm in the product. Methyl and methylene protons of CH3CH2NHPh group were observed at δ 3.01 and 1.12 ppm, respectively, in the product. The carbon NMR spectrum of the reaction product showed new peaks at δ 37.46 and 14.47 ppm that further confirmed secondary amine formation. The liquid chromatography coupled mass spectra peaks at 248–250 for 3,3′‐DDS and 304 for the reaction product further supported the formation of N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone. A blend of N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone with diglycidyl ether of bisphenol‐A (DGEBA) epoxy prepolymer started reacting at about 110–125°C surpassing an energy barrier of ∼ 66 kJ/mol as determined via differential scanning calorimetry analysis. Reaction kinetics were characterized via near IR spectroscopy specific to the reaction between secondary amine and DGEBA epoxy prepolymer. The results confirmed &gt;97% conversion at a cure protocol of 5 h at 80°C, 5 h at 100°C, 11 h at 125°C, and 6 h at 185°C. N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone‐DGEBA thermoplastics displayed tensile and flexural modulii of 3.08 and 2.86 GPa, respectively, and glass transition temperature (Tg) of 120.77°C. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis and properties of trifluoromethyl groups containing epoxy resins cured with amine for low Dk materials

AbstractThe study synthesized a trifluoromethyl (CF3) groups with a modified epoxy resin, diglycidyl ether of bisphenol F (DGEBF), using environmental friendly methods. The epoxy resin was cured with 4,4′‐diaminodiphenyl‐methane (DDM). For comparison, this study also investigated curing of commercially available diglycidyl ether of bisphenol A (DGEBA) with the same curing agent by varying the ratios of DGEBF. The structure and physical properties of the epoxy resins were characterized to investigate the effect of injecting fluorinated groups into epoxy resin structures. Regarding the thermal behaviors of the specimens, the glass transition temperatures (Tg) of 50–160°C and the thermal decomposition temperatures of 200–350 °C at 5% weight loss (Td5%) in nitrogen decreased as amount of DGEBF increased. The different ratios of cured epoxy resins showed reduced dielectric constants (Dk) (2.03–3.80 at 1 MHz) that were lower than those of pure DGEBA epoxy resins. Reduced dielectric constant is related to high electrronegativity and large free volume of fluorine atoms. In the presence of hydrophobic CF3 groups, the epoxy resins exhibited low moisture absorption and higher contact angles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Preparation of cationic latent initiators containing imidazole group and their effects on the properties of DGEBA epoxy resin

The thermal cationic latent initiators, N-benzyl-3-methylimidazolium hexafluoroantimonate (BMH1) and N-butyl-3-methylimidazolium hexafluoroantimonate (BMH2) were synthesized and applied to the thermal cationic polymerization of diglycidyl ether of bisphenol A (DGEBA). The performance of BMH1 and BMH2 was examined by differential scanning calorimetry (DSC), which showed good thermal latent properties and excelled epoxy resin curing behavior. The morphology, thermal, mechanical, and water sorption properties of DGEBA resin cured by 1 wt% of BMH1 and BMH2 were measured by X-ray diffraction (XRD), scaming electron microscopy (SEM), thermogravimetric analysis (TGA), nanoindentation, and thin film diffusion analysis. The cured DGEBA/BMH1 system showed relatively higher thermal stability than the DGEBA/BMH2 system. The diffusion coefficient and water uptake were 14.2×10−9 cm2/s and 1.15 wt% for the DGEBA/BMH1 system and 11.5×10−9 cm2/s and 1.07 wt% for the DGEBA/BMH2 system, respectively. Therefore, DGEBA/BMH2 showed higher resistance to water sorption than DGEBA/BMH1. On the other hand, hardness and elastic modulus of DGEBA/BMH2 were higher than those of DGEBA/BMH1. This can be attributed to the difference in the end group of initiators as well as the degree of crosslinking in the cured resin network. Open image in new window

Structure, thermal and fracture mechanical properties of benzoxazine-modified amine-cured DGEBA epoxy resins

First, traditional diamine hardeners of epoxy resins (EP) were checked as potential accelerators for the benzox- azine (BOX) homopolymerization. It was established that the acceleration effect depends on both the type and amount of the diamine compounds. In the follow-up work amine-curable diglycidyl ether bisphenol A (DGEBA) type EP was modi- fied with BOX keeping the EP/BOX ratio constant (75/25 wt.%). The amine hardeners, added in the EP in stoichiometric amounts, were of aliphatic and aromatic nature, viz. diethylenetriamine (DETA), 4,4!-diaminodiphenyl methane (DDM), and their 1/1 mixture. The thermal, viscoelastic, flexural and fracture mechanical properties of the EP/BOX hybrids were determined and compared to those of the reference EPs. Based on dynamic-mechanical thermal analysis and atomic force microscopy the formation of co-network between EP and BOX was concluded. Homopolymerized BOX was built in the network in nanoscaled inclusions and it was associated with internal antiplasticization. Incorporation of BOX improved the charring, enhanced the flexural modulus and strength, and reduced the glass transition of the parent EP. The fracture tough- ness and energy were not improved by hybridization with BOX.