Bisphenol A-based Epoxy Research Articles

Advanced hybrid materials from epoxy, oxidized UHMWPE fibers and silane surface modified silicon nitride nanoparticles

Aiming the development of highly performant polymer-based hybrid materials, the typical bisphenol-A based epoxy resin was reinforced with oxidized UHMWPE fibers and various amounts of silane surface modified silicon nitride (Si3N4) nanoparticles. The reinforcing phases underwent optimized surface modifications to create a fully connected network for an improved stress transfer between the constituents. The efficiency of the grafting methodology was confirmed by vibrational and morphological analyses. Meanwhile, the effects of the adopted modifications techniques on the mechanical properties were thoroughly discussed. Furthermore, static and dynamic mechanical investigations along with impact tests were conducted to study the effects of various amounts of Si3N4 nanoparticles on the overall performances of the epoxy/UHMWPE composite. The obtained results confirmed the great benefits from creating a fully connected hybrid network. The as such developed hybrids can be seen as promising materials for the intended use.

Enhancing the Recyclability of a Vegetable Oil-Based Epoxy Thermoset through Initiator Influence

Bisphenol A-based epoxy thermosets involve both environmental and health risks. By reacting a vegetal oil-based epoxide with an aromatic diacid containing S–S bonds a thermoset is produced. Herein, reprocessable thermosets were synthesized, the recyclability being designed through a dual mechanism: that of disulfide metathesis and of transesterifications. To assess the feasibility of the reprocessing, a series of 10 initiators was tested to probe their effect not only on the cross-linking reaction but also on the recyclability. This study introduces for the first time the key role of the initiator on the material performance and on their reprocessing. A very good reprocessability was obtained for thermosets prepared using as initiator the imidazole. Moreover, the thermosets exhibit complete chemical recyclability in 1 N NaOH at 80 °C, after 3 days, without needing additional chemicals. The reprocessed materials have similar performance with the virgin ones, even after 10 cycles of reprocessing.

Epoxy based hybrid nanocomposites: Fracture mechanisms, tensile properties and electrical properties

This work explore the effect of addition of a combination of rigid nanofillers and core–shell rubber nanoparticles on the fracture mechanics, tensile, electrical and thermo-mechanical properties of epoxy resins. SiO2 nanoparticles, multi-walled carbon nanotubes (MWCNT's), as rigid nanofillers, and core–shell rubber (CSR) nanoparticles, as soft nanofillers were used with bisphenol-A based epoxy resin. Further, the rigid fillers were added systematically with core–shell rubber nanoparticles and MWCNT’s to study the combined effect of rigid nanofillers and soft CSR nanoparticles. The resulting systems will be characterized by standard methods. This includes a thorough characterization of tensile, fracture mechanics, electrical, and thermal properties. The results show that the maximum increase of fracture toughness (207%) and fracture energy (910%) was obtained for system containing 5 wt% of CSR and 10% SiO2. The electrical conductivity threshold was obtained at 0.075 wt% of MWCNT’s modified system. The introduction of CSR nanoparticles significantly increase the fracture energy of the matrix with decrease in tensile strength and tensile modulus, which was further recovered with the addition of SiO2 nanoparticles. The analysis of the fracture surfaces revealed the toughening micro-mechanisms.

Chemical modification of SBS star block copolymer for templating nanostructures in epoxy resin blends

Star-shaped polystyrene-block-polybutadiene-block-polystyrene (SBS) block copolymer (BCP) was subjected to epoxidation reaction using m-chloroperoxy benzoic acid (MCPBA). The epoxidized SBS block copolymer (eSBS) was then blended with diglycidyl ether of bisphenol-A based epoxy resin (EP) and cross-linked with methylene dianiline (MDA). The materials were characterized by different techniques such as Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The FTIR spectrumwith the peak located at 890 cm−1 and 1230 cm−1 attested the occurrence of epoxidation reaction. The nanophase separated structures as demonstrated by transmission electron microscopy were induced in the eSBS/EP blends by epoxidized eSBS.

Curing behavior and properties of high biosourced epoxy resin blends based on a triepoxy monomer and a tricarboxylic acid hardener from 10-undecenoic acid

Renewable propane-1,2,3-triyl tris(9-(oxiran-2-yl) nonanoate) (EGU, 100 wt% biogenic) and a tricarboxylic acid triglyceride (CGTU) hardener (85.7 wt% biogenic) were synthesized from 10-undecenoic acid (10-UDA) and used to produce epoxy resins with 52–92 wt% biobased carbon. CGTU was prepared by thermally activated thiol-ene coupling of thioglycolic acid onto propane-1,2,3-triyl tris(undec-10-enoate), (GUD) in the absence of solvent. The characterized CGTU was used as a green hardener of blends based on EGU and a conventional bisphenol A-based epoxy pre-polymer (DGEBA) at various mass percentages (0–100 wt%) with an stoichiometric epoxy/acid equivalent ratio. Calorimetric studies revealed higher peak temperature, lower reaction heats, and longer gelation times in resins with high EGU proportion, evidencing the lower reactivity of aliphatic EGU compared with aromatic DGEBA. Cured resins were yellowish transparent rubber-like materials with glass transition temperatures (Tg) varying from −14 °C to −42 °C and tensile strength in the range of 1750 kPa–790 kPa, for 0 and 100 wt % EGU, respectively. The soluble fraction of all resins was less than 4.3%, reflecting a high level of crosslinking. Thermosets with high biobased content showed both UV-light protection and visible light transparency.

Prediction and optimization of epoxy adhesive strength from a small dataset through active learning

ABSTRACT Machine learning is emerging as a powerful tool for the discovery of novel high-performance functional materials. However, experimental datasets in the polymer-science field are typically limited and they are expensive to build. Their size (< 100 samples) limits the development of chemical intuition from experimentalists, as it constrains the use of machine-learning algorithms for extracting relevant information. We tackle this issue to predict and optimize adhesive materials by combining laboratory experimental design, an active learning pipeline and Bayesian optimization. We start from an initial dataset of 32 adhesive samples that were prepared from various molecular-weight bisphenol A-based epoxy resins and polyetheramine curing agents, mixing ratios and curing temperatures, and our data-driven method allows us to propose an optimal preparation of an adhesive material with a very high adhesive joint strength measured at 35.8 ± 1.1 MPa after three active learning cycles (five proposed preparations per cycle). A Gradient boosting machine learning model was used for the successive prediction of the adhesive joint strength in the active learning pipeline, and the model achieved a respectable accuracy with a coefficient of determination, root mean square error and mean absolute error of 0.85, 4.0 MPa and 3.0 MPa, respectively. This study demonstrates the important impact of active learning to accelerate the design and development of tailored highly functional materials from very small datasets.

Epoxidized soybean oil grafted with CTBN as a novel toughener for improving the fracture toughness and mechanical properties of epoxy resin

We prepared epoxidized soybean oil (ESO) grafted with carboxyl-terminated poly(acrylonitrile-co-butadiene) (CTBN) (ESO-g-CTBN) by a ring-opening reaction between the epoxide group and the carboxyl group. The structural features of the resulting product were determined using modern analytical techniques, such as Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, and gel permeation chromatography (GPC). The ESO-g-CTBN was applied as a toughener for an epoxy resin-based composite that was fabricated by blending the epoxy resin with diethylenetriamine (DETA) as the curing agent. The main aim of this procedure is to simultaneously improve the mechanical properties and fracture toughness of a bisphenol A-based epoxy resin. When 15 phr of ESO-g-CTBN was added to the EP/DETA mixture, the resin fracture toughness (KIC) and tensile strength increased from 0.65 to 1.09 MPa m1/2 and from 34.42 to 42.55 MPa, respectively. The ESO-g-CTBN existed in the EP matrix as a separate phase and induced an increase in the KIC via stopping crack growth or changing the crack direction. The epoxydized soybean oil grafted with CTBN (ESO-g-CTBN) was synthesized from ring opening reaction between epoxide group and carboxyl group. The ESO-g-CTBN help to improve the fracture toughness of epoxy resin by the mechanism as shown in the figure.

Designing of low-cost, eco-friendly, and versatile photosensitive composites / inks based on carboxyl-terminated quantum dots and reactive prepolymers in a mixed solvent: Suppression of the coffee-ring strain and aggregation

Today, solution processable quantum dots (QDs) are receiving great attention as photon down converters for various photoluminescent device architectures such as next-generation solid-state lighting (SSL) and micro-light emitting diodes (LEDs). However, fabrication of QDs in commercial applications is still limited due to the lack of suitable QD composites that can address current technical issues such as polymer induced QD aggregation, ring-like deformation (called the coffee-ring effect), and so on. In the present study, carboxyl-terminated QD based composites are proposed as a potential solution. As a ligand molecule for model carboxyl-terminated QDs, 3-mercaptosuccinic acid (MSA) was used and MSA-capped QDs (MSA-QDs) showed excellent dispersion properties (up to 70%, by weight) in industrial solvents such as propylene glycol monomethyl ether (PGME) and propylene glycol monomethyl ether acetate (PGMEA). For photosensitive composites (e.g., photoresist, ink), photoreactive bisphenol A-based epoxy resins (e.g., SU-8) and cardo-based acrylic resins as binders are studied under co-solvent systems. As a result, the bisphenol A-based composite (e.g., SU-8/MSA-QD composites) were found to exhibit good QD uniformity in the matrix. In addition, corresponding resin-based QD inks are shown to significantly suppress ring-like deformation in droplets when cyclopentanone (CP) is used as co-solvent.

Thermally Healable and Recyclable Graphene-Nanoplate/Epoxy Composites Via an In-Situ Diels-Alder Reaction on the Graphene-Nanoplate Surface.

In this work, thermally healable graphene-nanoplate/epoxy (GNP/EP) nanocomposites were investigated. GNPs were used as reinforcement and crosslinking platforms for the diglycidyl ether of bisphenol A-based epoxy resin (DGEBA) through the Diels-Alder (DA) reaction with furfurylamine (FA). The GNPs and FA could then be used as a derivative of diene and dienophile in the DA reaction. It was expected that the combination of GNPs and FA in DGEBA would produce composites based on the interfacial properties of the components. We confirmed the DA reaction of GNPs and FA at the interface during curing of the GNP/EP nanocomposites. This procedure is simple and solvent-free. DA and retro DA reactions of the obtained composites were demonstrated, and the thermal healing properties were evaluated. The behavior of the GNP/EP nanocomposites in the DA reaction is similar to that of thermosetting polymers at low temperatures due to crosslinking by the DA reaction, and the nanocomposites can be recycled by a retro DA reaction at high temperatures.

Evaluation of bisphenol A-based epoxy resin containing multiwalled carbon nanotubes to improve resistance to degradation

The influence of exposure to UV light and moisture on the durability of a multiwalled carbon nanotube(MWCNT)/epoxy nanocomposite was investigated. Samples of epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) cured with 2,2,4-trimethylene-1,6-hexadiamine (TMDA), and epoxy nanocomposite containing 0.5% MWCNT were exposed to different accelerated weathering times between one and six months. Changes in surface chemistry, mechanical properties (tensile tests), thermal properties (thermogravimetric analysis and differential scanning calorimetry), and morphology were evaluated before and after exposure to accelerated weathering for a period of up to six months. Epoxy nanocomposite (DGEBA–TMDA/0.5%MWCNT) samples had improved thermal stability and resistance to degradation, compared to epoxy resin (DGEBA–TMDA). The effect of MWCNT at reducing degradation was more pronounced than previously found for resins prepared with hydrogenated DGEBA.

A physico-mechanical investigation of a novel hyperbranched polymer-modified clay/epoxy nanocomposite coating

Abstract A series of epoxy-polyamide based nanocomposites is developed utilizing hyperbranched polymer (HBP)-modified nanoclay particles. To this aim, the pristine nanoclay is surface modified by a polyester-amide hyperbranched polymer (HBP) at various polymer to clay (P/C) ratios of 0.5, 1, 2.5, 5 and 10. The microstructure of the modified clays is investigated by X-ray diffraction (XRD) analysis. The results demonstrate that HBP adsorbs on the clay lamellae and the interlayer distance becomes larger due to interfacial interactions. The greater the P/C ratio is, the better intercalated morphology is obtained. In the next step, 1 wt.% of the pristine and modified nanoclay particles is introduced into a bisphenol-A based epoxy resin and the mixture is then cured by an amido polyamine based hardener to obtain nanocomposite specimens. Prior to curing process, the resulting dispersions undergo rheological measurements. The rheological behavior clarifies that HBP-modified nanoclay particles have reached to some extent to an exfoliated morphology. The inferred nanocomposites are then analyzed by XRD, thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA), tensile test and eventually scanning electron microscope (SEM) analyses. It is concluded by the outcomes that intercalated and/or exfoliated morphologies become more probable when the clays are modified by HBP and due to such nanostructure of the nanocomposites, the physical-mechanical characteristics are meaningfully enhanced.

Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials

Mechanically and thermally robust microcapsules containing diglycidyl ether bisphenol A-based epoxy resin and a high-boiling-point organic solvent were synthesized in high yield using in situ polymerization of urea and formaldehyde in an oil-in-water emulsion. Microcapsules were characterized in terms of their size and size distribution, shell surface morphology and thermal resistance to the curing cycles of commercially used epoxy polymers. The size distribution of the capsules and characteristics such as shell thickness can be controlled by the specific parameters of microencapsulation, including concentrations of reagents, stirrer speed and sonication. Selected microcapsules, and separated core and shell materials, were analysed using thermogravimetric analysis and differential scanning calorimetry. It is demonstrated that capsules lose minimal 2.5 wt% at temperatures no higher than 120°C. These microcapsules can be applied to self-healing carbon fibre composite structural materials, with preliminary results showing promising performance.

Development of technology to industrialise the production of 80000 MTPY epoxy resins

Purpose – The purpose of this paper is to establish a technology that is suitable for the production of the 80,000 MTPY series of epoxy resins on an industrial scale. Design/methodology/approach – This paper introduces the synthesis and processing of epoxy resins, including liquid epoxy resins (DGEBA) (E-51 and E-44), brominated bisphenol A-based epoxy resins (EX-23-80A), semisolid epoxy resins based on DGEBA (E-39D) and solid epoxy resins based on DGEBA (E-21). The study analyses the theoretical raw materials of epoxy resins per tonne, and lists an example of a distributed control system (DCS) to explain that the production process of 80,000 MTPY epoxy resins can be automated. Findings – A two-step method was used to produce either E-51 or E-44 sequentially in the pre-reactor, the reactor, the recycling kettle, refining kettle (1), the refining kettle (2) and the desensitizing kettle or the falling-film evaporator. An advancement process was adopted to manufacture EX-23-80A, E-39D and E-21 using E-51 as a raw material in the predominating kettle and the mixing kettle, the adding kettle (1) and the adding kettle (2), separately. All the processes were controlled automatically by DCS to yield the products. Originality/value – The results support the assertion that the technology developed by the authors ' company to produce 80,000 MTPY epoxy resins results in fewer side reactions and higher yield production.

A simple method to make mechanically robust, adhesive and superhydrophobic surface based on epoxy resin

A robust micro/nano-structured superhydrophobic surface was facilely prepared by applying composite coating consisting of epoxy resin and silica nanoparticles on glass substrates. The whole process only needed bisphenol A-based epoxy resin and silica nanoparticles to be mixed, coated, and dried. Field emission scanning electron microscopy, atomic force microscopy, and a drop meter were utilized to evaluate its morphology, accurate topography, quantitative roughness, and wettability, respectively. After considering adhesive force and the superhydrophobicity of the coating, it was shown that the best result was gained when the solid content of the silica nanoparticles was 45.5 wt%. In addition, the coating showed excellent surface mechanical stability and acid-alkali resistance which offers great potential for durable application in various fields.

Zirconium-methacrylate oxoclusters as new hybrid materials for the modification of epoxy systems

Oxozirconium clusters bearing methacrylate moiety (ZrMe) were synthesized by sol–gel process and used in epoxy networks to develop epoxy-based nanocomposites with potential application as encapsulant for light-emitting diode. Diglycidyl ether of bisphenol A-based epoxy resin was previously functionalized with acrylic acid to introduce some vinyl groups in the matrix and improve its interaction with the oxocluster. The ZrMe particles were previously dispersed in the epoxy matrix or in the 4-methyl-tetrahydrophthalic anhydride used as hardener, and the systems were cured with anhydride or with a combination of anhydride and benzoyl peroxide. The last compound promotes the covalent bond between the epoxy matrix and the ZrMe through free radical reactions between the vinyl groups. The dispersion of ZrMe into the epoxy matrix resulted in a significant increase in viscosity, mainly for systems dispersed with a combination of high shear mechanical mixing and ultrasonification. The dispersion of ZrMe into the anhydride resulted in nanocomposites with higher transparency, better dispersion of the oxocluster into the matrix bulk, as observed by transmission electron microscopy, and higher thermal conductivity, mainly for systems cured with anhydride and peroxide. The use of anhydride in combination with BPO also resulted in significant increase in glass transition temperature.

Effects of sepiolite clay on degradation and fire behaviour of a bisphenol A-based epoxy

As-received and pre-treated sepiolite/epoxy systems, characterised by an inorganic content from 2 to 10wt.%, were investigated in order to assess induced-filler effect on degradation and fire behaviour.Thermogravimetrical results show that the thermal stability of the hosting epoxy, is slightly affected by the presence of sepiolite for both typologies; whereas, changes induced in char morphology by the pre-treated clay will significantly affect the fire behaviour of the final nanocomposite.Modelling of thermo-gravimetrical results in air atmosphere, by means of Kissinger procedure, shows a noteworthy reduction of activation energies associated with each degradation steps, especially at highest sepiolite content either by using as-received and pre-treated inorganic filler. This substantially indicates that the presence of sepiolite shorten the whole degradation process on the temperature scale. On the other hand, the different morphology of the char layer during the burning process can have relevant flame retardant effects acting on both condensate and vapour phase. Analysing the cone calorimetric data, a reduction of about 27% of the peak of heat release rate for the highest sepiolite percentage is measured and the burning total period is increased thus confirming that sepiolite when pre-treated represents a valid fire retardant inorganic filler for such a system.

Synthesis of novel metal-containing epoxy polymers and their structural characterization by means of FT-IR and coupled TG/MS measurements

Novel copper containing epoxy polymers have been synthesized using copper(II) formamidine complex [Cu(ampf)Cl2], ampf = N,N′-bis(4-acetyl-5-methylpyrazole-3-yl)formamidine, as curing agent for diglycidyl ether of bisphenol A-based epoxy resins (Araldite and its oligomer consisting of 3–4 monomer units). The curing reaction was performed at room temperature without catalyst. In order to prove the polymerization reaction, differential scanning calorimetry (DSC) was applied. Highly exothermic peaks around 150 °C refer to the polymerization, and according to DSC results, the epoxy resins above 200 °C were almost completely converted to the corresponding metal-containing polymer. The proposed structure of the hybrid polymers was confirmed by FT-IR analysis. Gel permeation chromatography analysis shows that the average molar masses of the polymers are in the range from 3,000 to 50,000 g mol−1. The low conductivities of the hybrid materials in tetrahydrofuran confirm the non-ionic structure of the new polymers in solution. The thermal stability and the decomposition mechanism of the components of the reaction mixture and the new polymers were studied by coupled TG/DTA-MS measurements. The thermal data were analysed also with the aim to obtain additional information about the composition of the synthesized materials.

Synthesis and thermal properties of urethane-containing epoxy resin

A urethane-containing epoxy resin was successfully synthesized by reacting bisphenol A with 1,6-hexamethylene diisocyanate and epichlorohydrin. The chemical structure of urethane-containing epoxy resin was confirmed using FT-IR, 1HNMR, and elemental analysis. DSC results indicated that the initial curing and maximum exothermic peak temperatures of urethane-containing epoxy resin cured with 4,4′-diaminodiphenylmethane were 60°C and 135°C, respectively; these values were lower than those of a bisphenol A-based epoxy resin. The thermal stability of epoxy resins was studied using TGA, and it was found that the degradation temperature of urethane-containing epoxy resin was lower than that of bisphenol A-based epoxy resin under the same conditions.

Effect of functionalized magnetite nanoparticles and diaminoxanthone on the curing, thermal degradation kinetic and corrosion property of diglycidyl ether of bisphenol A-based epoxy resin

To prepare a high-performance epoxy resin with excellent thermal, chemical and corrosion stability, diaminoxanthone (DAX) was used to cure diglycidylether of bisphenol-A (DGEBA)-based epoxy resin and blend of DGEBA with functionalized Fe3O4 nanoparticles. Kinetic parameters of curing and thermal degradation of epoxy resin systems were estimated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The 10% weight loss temperature has been increased from 340 °C to 366 °C and there was an increase in the char yield from 32.6% to 45.3% for the above systems. The corrosion performance of epoxy coated carbon steel was examined by potentiodynamic polarization, along with immersion test in 1.0 mol/L HCl solution. The results showed that epoxy resins cured with DAX had low tendency to corrosion. In addition, the cured epoxy resin containing 10% Fe3O4 had higher anticorrosion activity than bare DGEBA system. The results showed that functionalized Fe3O4 nanoparticles enhanced char formation and improved the thermal stability as well as anticorrosion activity of the resin.

Effect of sepiolite filler on mechanical behaviour of a bisphenol A-based epoxy system

Sepiolite/epoxy systems, characterised by an inorganic content from 2% to 10% by weight, were tested by using different experimental techniques in order to assess the effects thermo-mechanical and fracture behaviour.It was found that filler dispersion is independent on the type of sepiolite used, i.e. hydrated and de-hydrated, whereas the addition of hydrated sepiolite strongly increases the viscosity of the final suspension. Mechanical properties have been investigated and discussed. The conservative modulus of the sepiolite/epoxy system increases as much as 21% and 94% respectively, at 35°C and 200°C respect to the unfilled polymer, with the incorporation of 10wt% of sepiolite, both hydrated and dehydrated, with a slightly increasing of the corresponding glass transition temperature. The effect of sepiolite on the coefficient of thermal expansion lead to a variation in both glassy and rubbery region, respectively of about 7–8% and 9%. Fracture toughness analysis revealed that the critical stress intensity factor negligibly changes by increasing the sepiolite content, whereas the critical strain energy release rate (GIC) reaches an noteworthy value around 30% higher than neat epoxy.