Diglycidyl Ether Of bisphenol-A Epoxy Resin Research Articles

Synergistic flame retardancy and electrical conductivity in di-glycidyl ether of bisphenol-A epoxy composites with polyaniline and aluminum Tri-hydroxide

This study focuses on developing and characterizing multifunctional composites based on the diglycidyl ether of bisphenol-A (DGEBA) epoxy matrix. The aim is to enhance fire resistance and electrical conductivity properties for applications in various fields. To achieve this, aluminum tri-hydroxide (ATH) was incorporated as a flame retardant (FR) agent, while polyaniline (PANI) was added to impart electrical conductivity. The composites were categorized into three groups: the first containing flame retardant (FR), the second containing PANI for conductivity, and the third containing both PANI and FR for combined effects. E 60-FP emerged as the optimal multifunctional composite, exhibiting superior mechanical properties among the tested formulations. Thermogravimetric analysis (TGA) results provided valuable insights into the thermal stability of E 60-FP, revealing that it retained 42% of its initial mass at a temperature of 600 °C. Additionally, the composite achieved a V-0 rating in the UL 94 test, confirming its excellent fire resistance. Notably, E 60-FP displayed impressive mechanical strength, with a tensile strength of 7.2 MPa and a tensile modulus of 1117.6 MPa. Its flexural strength and modulus were measured at 31.2 MPa and 2800.2 MPa, respectively. Furthermore, the composite E 60-FP exhibited remarkable electrical conductivity, measuring 6.1 × 10–6 S cm−1. These findings highlight the potential of DGEBA epoxy composites containing PANI and ATH as promising materials for applications requiring fire resistance and electrical conductivity properties.

Foaming epoxy-amine-carbamate: The effect of different neat amines on rheological and cellular morphology

The use of carbamate to foam epoxy depends significantly on the precured modulus to stabilize the cellular structure. The optimum precured modulus is developed from the reaction of epoxy resin and the neat amine. The selection of the neat amine relies on its reaction temperature with epoxy, which is required to be below the decomposition temperature of carbamate. This study investigates the effect of three different neat amines on the rheological behavior of foaming epoxy-carbamate-amine. They are bisphenol-A diglycidyl ether epoxy (DGEBA), isophorone diamine carbamate (IDPA.CO2), N-aminoethylpiperazine (AEP), 2,4-Diamino-1-methyl-cyclohexan (DMC) and isophorone diamine (IDPA). The mixtures of DGEBA-amine-carbamate are filled in 25% and 75% of the volume of a closed mold. Precuring is carried out at 60°C for 2 h. The foaming and complete curing are conducted at 180°C for 1 h. Having H-active at piperazine, AEP reacts with DGEBA faster and develops a higher precured modulus compared to DMC and IDPA. It is important to note that DGEBA-AEP-IDPA.CO2 exhibits viscoelastic behavior beyond 138°C, seen by its rheological storage modulus lower than loss modulus and its tan delta larger than 1. The reaction between DGEBA and the H-active piperazine of AEP leads only to linear linkage and is unable to further crosslink compared to the primary amine (-NH2). This results in a lower glass transition temperature Tg of DGEBA-AEP-IPDA.CO2. The effect of amine on foaming is more obviously at 25% filling level. DGEBA-AEP-IPDA.CO2 has more spherical and homogeneous cellular structure and the density of 285 kg/m3. Having quite similar chemical structure, both DGEBA-DMC-IPDA.CO2 and DGEBA-IPDA-IPDA.CO2 produce the epoxy foams having cell-interconnection and coalescence; their densities are also similar 301 kg/m3 and 305 kg/m3, respectively. All the foams are closed-cell at 75% of filling level. The cell morphologies are well reflecting the foaming modulus and tan delta behavior.

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.

Rethinking the Analysis of the Linear Viscoelastic Behavior of an Epoxy Polymer near and above the Glass Transition

In this communication, we propose a different approach for analyzing linear viscoelastic relaxation data that is more faithful to the underlying physics and naturally accommodates the thermorheological complexity that is observed in glass-forming polymers. Specifically, the linear viscoelastic behavior was evaluated for a diglycidyl ether of bisphenol-A epoxy cured with 4,4′-methylenedianaline with a glass transition temperature (Tg) of 101.5 °C. The dynamic storage and loss moduli were measured from 10–2 to 101.7 Hz for 19 temperatures between 90 and 180 °C. The experimental window was extended by two orders of magnitude using stress relaxation experiments for temperatures between 90 and 112.5 °C. The G′ and G″responses for this single-phase polymer are thermorheologically complex, thus precluding the construction of master curves via time–temperature superposition. The traditional method of determining the relaxation spectrum implicitly assumes a constant spectral density where the spectral strength cha...

Epoxidation of agricultural byproduct konjac fly powder and utilization in toughening and strengthening epoxy resin

In this work, an efficient renewable approach to the toughening and strengthening of epoxy resins is presented by using agricultural byproducts. The resulting epoxy exhibits low viscosity and good mechanical performance and thermal properties, without sacrificing stiffness. First, we synthesized epoxidized konjac fly powder (EKFP) from konjac fly powder, an agricultural byproduct. Subsequently, the resulting EKFP was successfully used as a green reactive diluent to simultaneously improve the toughness and strength of petroleum-based epoxy diglycidyl ether of bisphenol-A (DGEBA). The experimental results indicated that the free volume of the epoxy resins was increased with the incorporation of the EKFP. The fracture morphology of the resulting epoxy thermosets displayed shallow cleavages and roughness that contribute to the increased toughness. The addition of the EKFP to the DGEBA significantly improved the tensile strength, flexural strength, and impact strength of the resulting epoxy thermosets. The tensile strength, tensile modulus, flexural strength, impact strength, fracture toughness and fracture energy of epoxy thermosets with 20 wt% EFKP are increased by 61.2 %, 29.7 %, 24.5 %, 119.3 %, 83.3 % and 159.1 %, respectively. The enhancement of the toughness and strength was associated with the increased free volume and reduction in internal stress of the epoxy. The simultaneous reinforcement and enhancement of the resin’s toughness demonstrated the possibility to use the byproducts of konjac glucomannan production for the creation of high-performance bio-based epoxy thermosets, which have the potential to be employed in coatings, the aerospace industry, and various electronic applications.

Curing kinetics of bio-based epoxy resin-toughened DGEBA epoxy resin blend

In the present study, TEIA bioresin was blended with the diglycidyl ether bisphenol A (DGEBA) epoxy resin in different ratios (i.e. 10, 20, 30, 40 mass%), cured with methylhexahydrophthalic anhydride curing agent in the presence of 2-methylimidazole catalyst. The optimized composition of DGEBA and TEIA bioresin blends system was employed as an adhesive strength. The adhesive strength of the TEIA-modified DGEBA epoxy resin blend system was increased from 4.14 to 6.31 MPa on an aluminium substrate compared to the DGEBA epoxy resin. The curing kinetics of non-isothermal, DGEBA epoxy resin and its bio-based blend systems were investigated employing differential scanning calorimetry. An increase in the peak temperature and reduction in a heat of curing as well as activation energy in DGEBA epoxy resin were observed with the addition of TEIA bioresin content. The activation energy (Ea) of the DGEBA resin and their bio-based blend system were obtained from Kissinger and Flynn–Wall–Ozawa methods.

Synergistic effect of Ag and ZnO nanoparticles on polyaniline incorporated epoxy/2pack coatings for splash zone applications

In this work, epoxy/2pack coatings containing polyaniline (PANI) in combination with Ag and ZnO nanoparticles have been synthesized. The nanoparticles were incorporated with bisphenol-A diglycidyl ether epoxy resin and polyamino-amide. The mechanical properties of the fabricated coatings, such as the pendulum hardness, scratch resistance, and impact strength, were studied. The composition of the fabricated coatings was confirmed by attenuated total reflectance infrared spectroscopy measurements. The thermal degradation and indentations were characterized through the use of differential scanning calorimetry and nano-indentation techniques, respectively. The surface morphology of the fabricated coatings was characterized using field-emission scanning electron microscopy. The synergistic effects of the Ag and ZnO nanoparticles on the corrosion resistance of the coatings after different exposure periods in 3.5% NaCl solutions were determined by electrochemical impedance spectroscopy. All the results were consistent with one another and confirmed that the addition of Ag and ZnO nanoparticles improved the mechanical properties of the coatings. This effect also led to a notable increase in the corrosion resistance of the PANI coatings.

Reactions of DGEBA epoxy cured with diethanolamine: Isoconversional kinetics and implications to network structure

The curing of diglycidyl ether of bisphenol A (DGEBA) epoxy with diethanolamine (DEA) is studied. DEA has three reactive groups, a secondary amine hydrogen and two hydroxyls. The secondary amine reacts rapidly, forming an adduct containing tertiary amines, epoxides and hydroxyls. The epoxides and hydroxyls then react in the presence of the amines to crosslink and vitrify the epoxy in the “gelation” reaction. The gelation reaction, the subject of this study, is not simple. The reaction exhibits unusual dependencies on both temperature and degree of cure. Previously, the general mechanisms of this curing process were explored by a number of us. In the present paper, both differential scanning calorimetry (DSC) and isothermal microcalorimetry (IMC) are used to determine a number of characteristic times associated with the reaction. The characteristic times show that the reaction rate has different functional forms at different temperatures and extents of reaction. This results from the reaction rate not depending solely upon the temperature and over-all extent-of-reaction. The concentration of a number of auxiliary reactive species that are generated in the course of the reaction (as well as their mobility and steric hindrance) appear to be key factors in defining the reaction kinetics. The dependence of the final network structure on cure schedule for this type of tertiary amine activated reaction is then discussed in the context of the literature. Finally, in the Supplementary Material, Kamal-like functions are fit to the isothermal reaction kinetics, with the reader cautioned in applying the functions to non-isothermal cures.

Biobased flame retardants from tartaric acid and derivatives

Biobased flame retardants represent attractive alternatives to traditional organohalogen compounds which are persistent in the environment, tend to bioaccumulate and may pose risks to human health. Tartaric acid is generated annually in great abundance as a by-product of wine making. It is nontoxic and widely used as a food ingredient. It is tetrafunctional which provides broad opportunity for conversion to a wide spectrum of useful materials. It has been used as a base for the generation of a variety of new compounds that display good flame retardancy in DGEBA (diglycidyl ether of bis-phenol A) epoxy. These range from simple phosphinate and phosphonate esters to oligomeric materials containing bromine, in both saturated and unsaturated units, or bromine and phosphorus.

Enhanced flame retardancy of DGEBA epoxy resin with a novel bisphenol-A bridged cyclotriphosphazene

A novel flame retardant, namely bisphenol-A bridged penta(phenoxy)cyclotriphosphazene (A-BP), was synthesized and characterized successfully. Obtained A-BP was mixed in different proportions with diglycidyl ether of bisphenol-A (DGEBA) in order to prepare a series of flame retardant epoxy resins (EP). The differential scanning calorimeter (DSC) results indicated that the glass transition temperatures (Tg) of EPs containing A-BP had only a slight decrease in comparison to EP. Thermogravimetric analysis (TGA) showed that the incorporation of A-BP improves the thermal stability of EP at a high temperature. Moreover, an increase of LOI value (33.9%) was achieved for EP contained with 9 wt% of A-BP. Furthermore, such sample passed UL-94 V-0 rating. Additionally, according to the cone calorimeter tests, in the whole combustion, the EP/9% A-BP material showed lower heat release and smoke production than neat EP. To elucidate the flame retardant actions of A-BP for EP, comprehensive measurement including Fourier transform infrared (FTIR), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) and TG-FTIR techniques were adopted to analyze the char layers and gaseous products. As a result, a bi-phase flame retardant mechanism was proposed showing the efficiency of inert gas dilution and quenching of existed free radicals in gaseous phase and char formation action in a condensed phase, respectively.

Functional PDMS enhanced strain at fracture and toughness of DGEBA epoxy resin

The thermo-mechanical properties of diglycidyl ether of bisphenol-A (DGEBA) epoxy/silyl-diglycidyl ether terminated polydimethyl siloxane (PDMS) composites have been investigated; PDMS concentration was increased up to 15wt%. Differential scanning calorimetry (DSC) evidenced a phase separated microstructure as two glass transition temperatures, Tg, were detected: a high Tg at ca. 103°C corresponding to DGEBA phase, and a lower Tg at ca. 40°C. The lower Tg suggests interpenetration of PDMS into the DGEBA molecular network. SEM and AFM analyses confirmed the phase separated, droplet morphology, with well dispersed PDMS domains into the epoxy matrix. The PDMS droplets had diameters as small as 0.6μm, and the droplet size increased up to ca. 1.8μm at 15% PDMS content. Detailed EDS elemental mapping of the fractured composites evidenced siloxane residue in epoxy cavities suggesting incorporation of siloxane into the epoxy network, in agreement with DSC. Flexural testing showed a monotonic reduction of modulus (E) as PDMS content increased, as usually observed in rubber reinforced epoxy resins. However, strain at fracture and toughness increased twofold at about 10wt% PDMS content. Water contact angle increased and then decreased as PDMS content increased, reaching maxima at ca. 10wt% concentration. This behavior was apparently driven by surface roughness. The elastic mechanical modulus was found to scale with the droplet size of the rubbery phase.

Cure mechanisms of diglycidyl ether of bisphenol A (DGEBA) epoxy with diethanolamine

Abstract When diethanolamine (DEA) is used as a curative for a DGEBA epoxy, a rapid “adduct-forming” reaction of epoxide with the secondary amine of DEA is followed by a slow “gelation” reaction of epoxide with hydroxyl and with other epoxide. Through an extensive review of previous investigations of simpler, but chemically similar, reactions, it is deduced that at low temperature the DGEBA/DEA gelation reaction is “activated” (shows a pronounced induction time, similar to autocatalytic behavior) by the tertiary amine in the adduct. At high temperature, the activated nature of the reaction disappears. The impact of this mechanism change on the kinetics of the gelation reaction, as resolved with differential scanning calorimetry, infrared spectroscopy, and isothermal microcalorimetry, is presented. It is shown that the kinetic characteristics of the gelation-reaction of the DGEBA/DEA system are similar to other tertiary-amine activated epoxy reactions and consistent with the anionic polymerization model previously proposed for this class of materials. Principle results are the time-temperature-transformation diagram, the effective activation energy, and the upper stability temperature of the zwitterion initiator of the activated gelation reaction. It is established that the rate of epoxide consumption cannot be generically represented as a function only of temperature and degree of epoxy conversion. The complex chemistry active in the material requires specific consideration of the dilute intermediates in the reaction sequence in order to define a model of the reaction kinetics applicable to all time-temperature cure histories.

Co-curing effect of imidazole grafting graphene oxide synthesized by one-pot method to reinforce epoxy nanocomposites

Uniform dispersion of carbon nanomaterials in epoxy matrix is the most fundamental prerequisite to produce epoxy composites with high mechanical strength and high toughness. In order to enhance the interaction between graphene oxide (GO) and epoxy resin, imidazole (MZ) was introduced to GO covalently through isophorone diisocyanate (IPDI) up to the grafting ratio of 31 wt% in this work by one-pot method. This modified GO, GO-IPDI-MZ was capable to cure the diglycidyl ether of bisphenol-A epoxy completely at addition of ca. 33.3 wt%, showing a smooth exothermic peak with a maximum at 182 °C. To avoid aggregation of GO at so high content, the epoxy was co-cured by GO-IPDI-MZ together with 4,4′-diaminodiphenylmethane (DDM), and the cured epoxy composites exhibited maximum tensile strength, flexural strength, impact strength, and thermal conductivity when containing 0.80 wt% of GO-IPDI-MZ. SEM, X-ray diffraction, and thermogravimetry were used to investigate the structure and thermal stability of the cured epoxy composites. This research provides a new approach to disperse GO uniformly in epoxy and to enhance epoxy composites simultaneously by co-curing of curing reagent grafted GO.

Temperature dependence of isothermal curing reaction of epoxy resin studied by modulated differential scanning calorimetry and infrared spectroscopy

The isothermal curing reaction of bisphenol A diglycidyl ether epoxy (BADGE) resin with dimethyl diamino methane (DDM) hardener was investigated by means of modulated differential scanning calorimetry (MDSC) and infrared (IR) spectroscopy at 90, 100 and 120 °C.It was confirmed that the behavior of the bands assigned to the epoxy group, ether group, secondary amine and tertiary amine were different depending on temperature. At stoichiometric amounts of DDM and BADGE, the reaction at 90 and 100 °C compared with that at 120 °C, the oxirane or glycidyl group of epoxy resin and the secondary amine group were left even if reached at the end point of the reaction, and those reaction proceed as diffusion control continues longer. The reaction between 90 and 100 °C, it was different from the reactivity of the epoxy resin, various amino groups and ether group. Hence, the cured epoxy resin had a different composition. Moreover, it was also verified that the reactivity of the various amino groups and the etherification were difference, therefore, it was suggested that the cross-linkage construction of the cured resin at different temperature was different.

Isothermal curing kinetics and mechanism of DGEBA epoxy resin with phthalide-containing aromatic diamine

The curing reaction of diglycidyl ether of bisphenol A (DGEBA) with a novel aromatic diamine containing phthalide structure (BAPP) was studied by differential scanning calorimetery (DSC). The optimal formulation of DGEBA/BAPP system was obtained in terms of the curing behavior and glass transition temperature determined by dynamic DSC. The nth-order reaction model and autocatalytic model were used to analyze the curing kinetics and mechanism based on the isothermal DSC technique. The results indicated that the Kamal autocatalytic model had a great agreement with the experimental data from the start of curing reaction to the initiation of diffusion control stage. Diffusion-controlled effect was also taken into account and then the extended Kamal model could describe precisely the curing reaction of BAPP/DGEBA in the entire conversion range.

Fabrication and evaluation of acrylated epoxidized castor oil‐toughened diglycidyl ether of bisphenol A nanocomposites

AbstractCastor oil‐based epoxy monomer was prepared using a two‐step approach: epoxidation of castor oil, followed by acrylation of epoxidized castor oil. A bio‐based diglycidyl ether of bisphenol A (DGEBA) epoxy nanocomposites was prepared by the incorporation of organo‐modified montmorillonite (OMMT) clay to the DGEBA/AECO system. The cured bio‐based DGEBA epoxy nanocomposites at 0.80:0.2:0.001 g/g exhibited higher tensile strength (56 MPa), tensile modulus (1933 MPa), flexural strength (132 MPa), flexural modulus (2518 MPa), elongation (23.1 %), and impact strength (34 kJ/m2). The nanocomposites at 0.6:0.4:0.001 g/g can easily bend up to 360° without any damage; similarly, the 0.8:0.2:0.001 g/g system can bend up to 180°. Thermal behaviour of the bio‐based epoxy systems was characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The obtained nanocomposites displayed a higher char yield (8.9 %) at 700 °C and glass transition temperature (108 °C) than the DGEBA/AECO systems. Further SEM analysis was used to study the morphological changes in the fractured surfaces of bio‐based epoxy systems, which reveals that crack propagation decreases with addition of AECO to the DGEBA epoxy system.

Epoxidized castor oil toughened Diglycidyl Ether of Bisphenol A epoxy nanocomposites: structure and property relationships

The present study highlights the structure and property relationships of epoxidized castor oil (ECO) toughened Diglycidyl Ether of Bisphenol A (DGEBA) epoxy nanocomposites. Toughened epoxy systems have been prepared by an addition of 10–40 wt% ECO to the DGEBA epoxy resin. Nanocomposites were prepared by mixing small amounts of Cloisite 30B (C30B) clay and 3‐aminopropyltriethoxysilane to the DGEBA/ECO blends. The chemical structure of toughened systems was confirmed using proton nuclear magnetic resonance and fourier transform infrared spectroscopy. The triethylenetetraamine‐cured DGEBA/ECO/C30B (8:2:0.1) nanocomposites exhibited tensile strength (50 MPa), tensile modulus (1.7 GPa), flexural strength (120 MPa), flexural modulus (3.02 GPa), and elongation (19%). The fracture toughness (critical intensity factor, KIC) and fracture energy (critical energy release rate, GIC) of DGEBA/ECO/C30B (8:2:0.1) system found to be higher than the other systems (2.5 MPa.m1/2 and 1.8 kJ/m2 for KIC and GIC, respectively). The thermal stability and heat of reaction of DGEBA/ECO blends increase with the addition of C30B clays that were analyzed using thermogravimetric analysis and differential scanning calorimetry. Rheological characterizations of uncured samples revealed a pronounced effect of the C30B clay on the DGEBA/ECO blend systems that exhibited a shear‐thickening behavior. On the other hand, the dynamic mechanical properties also revealed that the addition of C30B clays to the DGEBA/ECO blend a significant enhancements in viscoelastic and cross linking density behavior. Scanning electron microscope analysis was used to study the fractured morphology of DGEBA, DGEBA/ECO, and its nanocomposite systems. Copyright © 2015 John Wiley & Sons, Ltd.

Tough, natural-fibre composites based upon epoxy matrices

Flax fibres and cellulose fibres were used to manufacture composites with particle-modified epoxy matrices in order to develop ‘green’ composites which possess relatively high values of interlaminar fracture energy, G c. The flax used had a unidirectional architecture of continuous yarns spun from short, interlocked fibres. The regenerated cellulose consisted of continuous and non-twisted pure cellulose fibres in a plain-woven architecture. The natural-fibre-reinforced-polymer (NFRP) composites employed an anhydride-cured diglycidyl ether of bisphenol-A epoxy as the matrix. The epoxy polymeric matrix was modified with (a) silica nanoparticles, (b) rubber microparticles, and (c) a combination of both of these types of particles to give a hybrid-toughened epoxy matrix. The composites were manufactured via a resin infusion under flexible-tooling (RIFT) process. Preliminary studies on the NFRP composites manufactured using the initial-RIFT process clearly showed the deleterious effect that moisture present in the natural fibres had upon the properties of the NFRP composites, since the trapped water cannot escape from the composite panel. Hence, an optimised-RIFT process was developed whereby the natural fibres were dried in a fan oven prior to being employed in the RIFT process. This reduced the water content of the fibres from around 9 to 10 wt% to about 1 wt%. Significant improvements in the physical and mechanical properties were recorded for the NFRP composites manufactured using this optimised-RIFT process. Indeed, in particular, very dramatic improvements in the G c of the NFRP composites were measured, especially when the epoxy polymeric matrix was modified using the silica nanoparticles and/or rubber microparticles. For example, a steady-state propagation value of G c of about 1935 J/m2 was measured for the flax–fibre composite with the hybrid epoxy matrix, compared to values of 1110 and 535 J/m2 for the flax–fibre and glass–fibre composites based on the unmodified (i.e., the ‘control’) epoxy matrix, respectively.

Epoxy-functionalized star-shaped polymers as novel tougheners for epoxy resin

A novel epoxy resin toughener based on star-shaped copolymer of butyl acrylate (BA) and glycidyl methacrylate (GMA) [poly (BA-co-GMA)] with low viscosity was developed. The star polymers were synthesized by initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) using tri, tetra and hexa-functional initiators. The branching parameters of star poly (BA-co-GMA) were characterized by gel permeation chromatography with a laser light scattering-viscometry triple detection system. Copolymer composition and glass transition temperatures of the copolymers were analyzed by proton nuclear magnetic resonance (1H-NMR) and differential scanning calorimetry (DSC), respectively. The results showed that the branching ratio decreased as the number of arms increased. The epoxide groups of the GMA units were kept intact during ICAR ATRP. Rheological, mechanical tests and dynamic mechanical analysis revealed that star poly (BA-co-GMA)/diglycidyl ether of bisphenol A (DGEBA) epoxy resin formulation exhibited better processability, higher impact resistance and thermal resistance than those of linear poly (BA-co-GMA)/DGEBA epoxy resin formulation.

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