Diglycidyl Ether Of Bisphenol A Matrix Research Articles

Sustainably sourced and DOPO-derived triols as hardeners for epoxy thermosets: A promising solution to synchronously improve flame retardancy, mechanical strength and toughness

The flammability and brittleness of the diglycidyl ether of bisphenol A (DGEBA)-type epoxy resin greatly restrict its application in electronic appliances and structural materials. However, the synchronous improvement in the flame retardancy, mechanical strength, and toughness of DGEBA-type epoxy thermosets remains a significant challenge. To overcome this challenge, in this study, a sustainably sourced and DOPO-derived triol (DOPO-GL-DCDA) was synthesized from a bio-based material, glycerol 1, 3-diglycerolate diacrylate (GL-DCDA). A series of epoxy thermosets with different phosphorus contents were prepared by introducing DOPO-GL-DCDA into the DGEBA matrix. EP/DOPO-GL-DCDA demonstrated excellent flame retardancy and mechanical properties without compromising transparency. Specifically, EP/DOPO-GL-DCDA-1.0P exhibited a limit oxygen index (LOI) of 34.0 % and a UL-94 V-0 rating, and the total heat release (THR) and peak heat release rate (PHRR) of EP/DOPO-GL-DCDA-1.5P decreased by 36.6 % and 46.8 %, respectively, compared with those of pure EP. In addition, compared with those of pure EP, the tensile strength, impact strength, fracture toughness (KIC), and fracture energy (GIC) of EP/DOPO-GL-DCDA-1.5P increased by 62.8 %, 69.9 %, 62.9 %, and 99.0 %, respectively. Moreover, EP/DOPO-GL-DCDA had better dielectric properties than pure EP. Under the premise of maintaining transparency, this work provided a promising solution to synchronously improve the flame retardancy, mechanical strength, and toughness of epoxy thermosets.

Improved thermal conductivity of epoxy resins using silane coupling agent‐modified expanded graphite

AbstractA silane coupling agent was used to modify the surface of expanded graphite (EG), which was subsequently used as a thermally conductive filler to fabricate diglycidylether of bisphenol‐A (DGEBA)/EG composites with high thermal conductivity via hot blending and compression‐curing processes. The surface characteristics of silane coupling agent‐modified EG (Si@EG) were characterized by a variety of analytical techniques. The effects of the Si@EG content on the thermal conductivity, thermal stability, impact strength, and morphology of the DGEBA/Si@EG composites were investigated. The results revealed that the addition of 80 wt.% Si@EG increased the thermal conductivity of the composites from 0.17 to 10.56 W/m K, which was 61.1 times higher than that of pristine DGEBA. The initial decomposition temperature of the composite containing 80 wt.% Si@EG was 60.6°C higher than that of pristine DGEBA. The impact strength of the composites decreased from 2.0 to 0.87 kJ/m2 when the Si@EG content increased from 0 to 80 wt.%. The scanning electron microscopy images of the fractured surfaces revealed that the EG sheets in the DGEBA matrix formed a continuous thermally conductive path at high Si@EG contents.

Rheological and Electrical Study of a Composite Material Based on an Epoxy Polymer Containing Cyclotriphosphazene.

In this work, we have studied, formulated, prepared, and characterized the rheological and electrical behavior of a composite material based on an epoxy resin Diglycidyl Ether of Bisphenol A (DGEBA) reinforced with hexaglycidyl cyclotriphosphazene (HGCP). The epoxy system was cured with 4,4’-methylene dianiline (MDA). DGEBA-HGCP-MDA epoxy composite materials with reinforced HGCP which varied from 5% to 10% by weight were prepared by mixing in the molten state. The morphology was evaluated by SEM. The rheological behavior was studied using small deformation rheology. The electrical characterization was carried out with a frequency variation range from 1 Hz to 100 KHz at room temperature. These measurements revealed that the rheological and electrical behaviors strongly depend on the quantity of HGCP in the DGEBA matrix. The linear viscoelastic properties study reveals that the modulus of elasticity G’ is dependent on the amount of HGCP present in the epoxy resin DGEBA. The capacitance-frequency measurements suggest a distribution of localized states in the band gap of the blends.

Synthesis of a novel flame retardant based on cyclotriphosphazene and DOPO groups and its application in epoxy resins

A novel flame retardant additive with phosphazene and phosphaphenanthrene groups hexa-[4-(p-hydroxyanilino-phosphaphenanthrene-methyl)-phenoxyl]-cyclotriphosphazene defined as CTP-DOPO was successfully synthesized from hexachlorocyclotriphosphazene, p-hydroxybenzaldehyde, 4-aminophenol and 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO). Its chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (1H NMR) and 31P nuclear magnetic resonance (31P NMR). The prepared flame retardant additive CTP-DOPO was incorporated into diglycidyl ether of bisphenol-A (DGEBA) to prepare flame retardant epoxy resins thermosets. The flame retardant properties, thermal degradation behavior and combustion behavior of the DGEBA thermosets cured by 4, 4′ -Diamino-diphenyl sulfone (DDS) were investigated by limiting oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis/infrared spectrometry (TG-IR) and cone calorimeter tests. The structure and surface morphology of the char residues after cone calorimeter tests was measured by FTIR and scanning electron microscopy (SEM). The results revealed that DGEBA/CTP-DOPO thermosets successfully passed UL-94 V-0 flammability rating and its LOI value dramatically increased from 21.7% for cured pure DGEBA to 36.6% when the loading amount of CTP-DOPO was 10.6 wt % and the phosphorus content was only 1.1 wt % in thermosets, which indicated that the prepared CTP-DOPO possessed excellent flame retardancy for DGEBA thermoset. The TG-IR results indicated that the introduction of CTP-DOPO stimulated epoxy resins matrix decomposed and char forming ahead of time, which led to a higher residual char and thermal stability for epoxy resins thermosets at high temperature. The cone calorimeter tests revealed that the incorporation of CTP-DOPO effectively reduced the combustion parameters of DGEBA thermosets, such as heat release rate (HRR), total heat release (THR), smoke production rate (SPR) and total heat production (TSP), and so on. The SEM results showed that the phosphazene and phosphaphenanthrene groups in CTP-DOPO obviously stimulated the formation of the intumescent, compact and strong char layer, which enhanced the flame retardany of the DGEBA matrix during combustion. Therefore, the underlying materials were protected from further degradation and combustion and resulted in the efficient flame retardancy for EDGEBA thermoset.

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.

Controlled network structure and its correlations with physical properties of polycarboxyl octaphenylsilsesquioxanes-based inorganic–organic polymer nanocomposites

Polycarboxyl octaphenylsilsesquioxanes (polycarboxyl-OPS) containing different numbers of reactive carboxyl groups per OPS molecule were synthesized, which were then utilized as nanofillers and macromolecular cross-linkers to cure diglycidyl ether of bisphenol-A (DGEBA) to yield a series of novel inorganic/organic polymer nanocomposites. The network structures and cross-linking densities were modulated by varying the contents of polycarboxyl-OPS in the system. The interface between OPS and DGEBA matrix was remarkably enhanced by the strong covalent bonds as evidenced by the complete disappearance of the carboxyl absorption at 1699 cm−1, the epoxy group at 915 cm−1 and the newly emerged strong peak of ester bond at 1725 cm−1 in the FTIR spectra. All the OPS/DGEBA cured samples are transparent, and the wide angle X-ray diffractions (WAXD) exhibited similar amorphous patterns to the pure DGEBA resin, whereas the peak at ∼8° corresponding to OPS aggregations were absent, indicating a homogeneous dispersion of OPS within the DGEBA matrix. The correlations between network structures, viscoelastic behaviors, cross-linking densities, inter-segmental distances, glass transition temperatures, flexural properties and thermal stability of OPS/DGEBA products were systematically investigated by means of dynamic mechanical analysis (DMA), DSC, TGA, scanning electron microscopy (SEM) and WAXD methods.

Thermal Insulation Properties of Epoxy/Mesoporous Carbon Composites

This study aimed to investigate the influence of mesoporous carbons on the thermal insulation properties of epoxy/mesoporous carbon composites. The mesoporous carbon (CMK-3) was prepared by conventional templating method using SBA-15. The epoxy/mesoporous carbon composites were prepared by mixing the synthesized CMK-3 with diglycidylether of bisphenol A (DGEBA). As experimental results, the curing reactivities of the DGEBA/CMK-3 composites were found to decrease with the addition of the CMK-3. Also, the thermal conductivities of DGEBA/CMK-3 composites were found to decrease with increasing CMK-3 content. This could be interpreted in terms of the slow thermal diffusion rate resulting in pore volume existing in the gaps in the interfaces between the mesoporous carbon and the DGEBA matrix.

Effect of silane coupling agent on the dielectric and thermal properties of DGEBA-forsterite composites

Diglycidyl ether of bisphenol A (DGEBA) -forsterite composites have been prepared through mechanical mixing process and the influence of silane coupling agent on the microstructure, dielectric and thermal properties were studied. Phase pure forsterite (Mg2SiO4) powder was prepared through solid state ceramic route. Filling fraction of forsterite in DGEBA matrix was varied from 10 to 40 vol%. The morphology and filler distribution of filled composite were studied by Scanning Electron Microscopy. Waveguide cavity perturbation technique was employed to measure the dielectric properties of composites. It is found that aminosilane treatment increased the dielectric constant and dielectric loss of the composites in both microwave and radio frequency ranges compared to composites prepared using untreated powders. Coefficient of thermal expansion of composites decreased with the forsterite addition and attains a relatively low value of 45 ppm/°C for composite containing 40 vol% surface treated filler.

Electrical properties of the DGEBA/PANI-Ag composites

The metallopolymer polyaniline-silver (PANI-Ag) was synthesized and used as conductive filler in crosslinked diglycidyl ether of bisphenol A (DGEBA) epoxy network. The hybrid organic/inorganic PANI-Ag powders were successfully synthesized via in situ chemical oxidation of polyaniline-emeraldine base (PANI-EB) by the capped Ag+ on the polyaniline-emeraldine base (PANI-EB) surface. The UV–Vis and FT-IR spectra confirmed the pernigraniline structure (PN) of PANI in the hybrid PANI-Ag. The PANI-Ag dispersion in epoxidic matrix was analyzed by optical microscopy (OM). The images analysis from OM showed that the particle agglomerate size of the metallopolymer increased with increasing PANI-Ag concentration in the DGEBA composite, owing to the aggregation effect. The dc conductivity and impedance spectroscopy of the DGEBA/PANI-Ag composite was measured at different PANI-Ag concentrations in the DGEBA network. The electrical dc conductivity of the PANI-Ag was 35.1 S cm−1 and was dependent of the PANI-Ag concentration in DGEBA matrix. The real and imaginary part of impedance complex measurements indicates a strong interfacial polarization at low frequency for both PANI-Ag and DGEBA/PANI-Ag, respectively. The imaginary part of impedance complex Im(Z) data decrease with the PANI-Ag hybrid concentration in the frequencies range of 102–106 Hz. The dependence of the Im(Z) on the frequency exhibited a relaxation process in both, PANI-Ag and DGEBA/PANI-Ag composite with 10 phr of PANI-Ag powder.

Aging behavior of a hot‐cured epoxy system

AbstractThe thermal and hydro‐thermal aging of a hot‐cured epoxy system (diglycidylether of bisphenol A (DGEBA) + dicyandiamide (DDA)) in the glassy state is revisited using DSC and IR attenuated total reflection spectroscopy. Because of the diffusion of DDA from the solid particles into the liquid DGEBA matrix, curing produces a highly crosslinked amorphous matrix that contains low crosslinked amorphous regions. After full curing, the network possesses a relatively low molecular mobility and no residual reactive groups. Thermal and hydro‐thermal loading is performed at 60°C, well below the principal glass transition temperature (Tg1 = 171°C). Both aging regimes cause significant chemical and structural changes to the glassy epoxy. It undergoes a phase separation of relatively mobile segments inside the low mobile matrix, providing a second glass transition that shifts from Tg2 = 86–114°C within 108 days of aging. This phase separation is reversible on heating into the viscoelastic state. Hydro‐thermal aging leads to a reversible and a nonreversible plasticizing effect as well. On thermal aging, no chemical changes are observed but hydro‐thermal aging causes significant chemical modifications in the epoxy system. These modifications are identified as a partial degradation of crosslinks produced by the cyano groups of the DDA and correspond to the nonreversible plasticitation. These changes in the cured epoxy should exert an influence on the mechanical properties of an adhesive bond. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

Time‐resolved method for the measurement of volume changes during polymerization

AbstractA new laser scanning dilatometer, based on a simplified capillary‐type dilatometer using a laser scan micrometer for the detection of changes of the sample dimension, is described. The method can be applied to time‐resolved measurements of volume changes for transparent and nontransparent samples. The time resolution of the setup is below 1 s, the absolute error in determining the volume change is below 0.0004 cm3, and the accuracy of the measured shrinkage is better than 0.2 vol. %. The operation temperature ranges from room temperature to 160 °C. The setup has been applied to the investigation of the volume shrinkage during the curing of epoxy resins [diglycidyl ether of bisphenol A (DGEBA)] without and with fillers. Furthermore, the effect of a phase transformation on the volume has been demonstrated by the melting of a crystalline phase (succinic anhydride) dispersed in a DGEBA matrix due to the heat of reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2314–2325, 2005

Clay‐reinforced epoxy nanocomposites

AbstractEpoxy/clay nanocomposites were prepared using a conventional diglycidyl ether of bisphenol A (DGEBA) epoxy, cured with diethyltoluene diamine (DETDA). The nanocomposites were characterized by dynamic mechanical analysis. A modest increase in glass transition temperature and significant increase in storage modulus were achieved as a result of incorporation of clay. The formation of nanocomposite was confirmed by wide‐angle X‐ray analysis. The higher impact strength of the nanocomposite compared the DGEBA matrix was explained in terms of with the morphology observed by SEM.© 2003 Society of Chemical Industry

Studies on blends of epoxy-functionalized hyperbranched polymer and epoxy resin

An epoxy-functionalized hyperbranched polymer (HBP) was used to toughen a conventional epoxy resin, diglycidyl ether of bisphenol A (DGEBA) cured with diethyltoluene-2,6-diamine (DETDA). There was little change in gel time as a result of addition of HBP, even though the HBP reacts at a slower rate with amine hardeners compared to DGEBA alone. Phase separation was investigated for various HBP contents and as a function of cure conditions as well. The thermal and dynamic viscoelastic behavior of the modified matrices have been examined and compared to the DGEBA epoxy matrix. It appears that the HBP which phase separates does not react as fully as when it is reacted with the amine alone. Nonetheless, good improvement in impact strength as a result of incorporation of HBP were observed and explained in terms of morphological behavior for a DGEBA matrix modified with various amounts of HBP.

Preparation and properties of polydimethylsiloxane-modified epoxy resins

In this work, polydimethylsiloxane (PDMS) with different molecular weight were used to modify diglycidyl ether of bisphenol A (DGEBA). A PDMS-block-DGEBA copolymer that acted as a compatibilizer was prepared via DGEBA, hydroxy terminated PDMS, and silane coupling agent in the presence of a catalyst. The reaction mechanisms and compatibilizing effects of the block copolymer were studied by means of Fourier transform infrared (FTIR) spectrum analysis and observation under scanning electron microscopy (SEM). The thermal and mechanical behaviors were analyzed as well. Results indicated that the block copolymer has good compatibilizing effect, and PDMS with low molecular weight could be dispersed in the DGEBA matrix more evenly. Moreover, the PDMS modified DGEBA systems had higher impact strength and lower weight loss rate than those of the pristine DGEBA system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1683–1690, 2000

Polyurethane‐crosslinked epoxy resins. II. Compatibility and morphology

AbstractThe polyurethane(PU)‐crosslinked diglycidyl ether of bisphenol A (DGEBA) was prepared from the reaction of the pendent secondary hydroxy group in DGEBA with the isocyanate‐terminated group present in the PU prepolymer. Though the PU acted as a crosslinking agent for the DGEBA, the morphology and dynamic mechanical behaviour of these PU‐crosslinked DGEBA could be different among themselves depending on the type and molecular weight of polyols employed in the PU. There was no significant shift in the loss modulus (E″) peaks of the DGEBA crosslinked with the polyester‐type and polyether‐type polyurethanes, but the intensity of the E″ peaks increased as the polyester‐type PU employed. The morphology of this polyester‐type PU‐crosslinked DGEBA exhibited a homogeneous one‐phase system, while the DGEBA crosslinked with the polyether‐type PU showed a two‐phase morphology with the PU particles dispersed in DGEBA matrix.