Epoxy Equivalent Weight Research Articles

Improving flame retardancy in BADGE epoxy via novel phosphorus‐functionalized epoxy integration

AbstractA novel epoxy resin, DPHP, was synthesized from diphenolic acid, which contains biobased levulinic acid, with triethylphosphite, to improve the flame retardancy of bisphenol‐A diglycidyl ether (BADGE) epoxy. Curing experiments were conducted using isophorone diamine as a curing agent for BADGE and DPHP mixtures. Variations in cure kinetics, mechanical properties, and flame retardancy were evaluated across different DPHP contents. The introduction of phosphorus functional groups into DPHP affected the polarization of epoxide CO bonds, resulting in reduced apparent activation energy for epoxy curing reactions. However, the higher epoxy equivalent weight of DPHP compared with that of BADGE led to a decrease in the tensile strength and the glass transition temperature of the cured material with increasing DPHP content. A significant increase in char yield for combustion of the epoxy blend was observed, ranging from 8.3% at 0 wt% DPHP to 20.1% at 50 wt% DPHP. Additionally, cone calorimeter measurements showed significant reductions in heat release rate and total heat release, leading to a decrease in fire spread from 1.07 MJm−2 s−1 at 0 wt% DPHP to 0.43 MJm−2 s−1 at 50 wt% DPHP. These results show that the flame retardancy of the cured material improved significantly as the DPHP content increased.

Upgrading of kraft lignin with phosphoric acid purification: A promising route for the synthesis of renewable epoxy resins

Obtaining bioproducts of industrial interest from kraft lignin not only adds value to this residual biomass while reducing environmental impact, but also fosters the circular economy and promotes sustainable development. However, its use without the removal of ash, metals, sulfur, and nitrogen implies a reduction in the final product properties, limiting its applications. This study aims to present a simple and efficient route for the production of purified kraft lignin (LKP) with low ash 0.51% and total sulfur 0.74% content. It is produced from impure kraft lignin (LKI), with high ash 9.74% and total sulfur 1.39% content which was treated with hot H3PO4/H2O solution (dilute acid purification), aiming at the synthesis of lignin-based epoxy resins. Elemental Analysis of carbon (C), hydrogen (H), and nitrogen (N) (wt%); ash (wt%); total sulfur (wt%); moisture contents (wt%); X-ray Fluorescence; X-ray Diffraction; Infrared Spectroscopy; Thermogravimetric Analysis; and Differential Scanning Calorimetry showed that LKP improved its structural, functional; and chemical properties, particularly thermal properties: 17% increase initial decomposition temperature (Tonset), 18% decrease final decomposition temperature (Tendset), 14% increase maximum decomposition temperature (Tdmax.), 35% increase carbonaceous residue (CR) and 8% increase in the value of glass transition temperature (Tg). The limiting oxygen index (LOI) calculated for this sample was around 34%, thus configuring a “self-extinguishing” material. Moreover, its high phenolic and aliphatic hydroxyl content 8.02 mmol L−1, high aromaticity (H/C = 1.11), high weight average molar mass (Mw̅≅1900g mol−1), and ash and total sulfur low contents justify its use in the synthesis of lignin-based epoxy resins. A sample of LKP was tested in a classic epoxidation reaction to obtain the prepolymer denominated of lignin-based epoxy resin (E-LKP), whose epoxy equivalent weight (EEW) was around 3500 g mol−1, which is similar to that of the high molar mass epoxy resin, D.E.R. 668-20 2000, commercialized by Dow Chemical Company®. E-LKP was polymerized with a conventional curing agent (polyetheramine) to produce the cured lignin-based epoxy resin (R-ELKP) with good physical-chemical properties. The high glass transition temperature (Tg2 = 133 ºC), a good limiting oxygen index (LOI = 27%), and excellent aesthetic characteristics (homogeneity and high brightness) stand out. These promising results suggest that it is possible to develop cured lignin-based epoxy resin with properties comparable to cured petroleum-based epoxy resin. The use of purified kraft lignin to obtain materials (prepolymers and polymers epoxy, among others) will also favor the environment, developing greener and renewable products.

Design and synthesis of epoxy prepolymer containing aromatic imide structures for thermoset with excellent thermal, mechanical and dielectric properties

Recently, the development of epoxy thermosets with imide rings has received extensive attention due to their superior integrated properties, especially for thermal, mechanical and dielectric properties, compared to those of commercialized bisphenol A epoxy thermosets, yet remains substantial challenges, such as the high epoxy equivalent weight (EEW) of the epoxy prepolymers and the poor processibility of the epoxy systems. In this work, an imide-containing epoxy prepolymer (BAPT-EP) was facilely synthesized. It had a relatively low EEW of 340 g/equiv. and could be dissolved in hardener methylhexahydrophthalic anhydride (MHHPA) to give a homogeneous BAPT-EP/MHHPA system with good processibility. Thanks to the aromatic imide structures, the cured BAPT-EP/MHHPA showed improved overall properties. In particular, it had a 47.9 °C, 24.7 °C, 29.4%, 77.3% and 10.0% increase in the glass transition temperature, temperature at 5% mass loss, tensile strength, Young’s modulus and tensile toughness, respectively, compared to those of bisphenol A epoxy prepolymer (DGEBA)/MHHPA thermoset. Meanwhile, BAPT-EP/MHHPA thermoset featured good charring ability with a high char yield of 26.4% (800 °C/N2), remarkable dimensional stability with a low coefficient of thermal expansion of 52.5 ppm/°C and good dielectric properties with a low dielectric constant of 3.24 at 100 MHz. This work provides an elegant strategy to prepare high-performance epoxy thermosets with imide structures, which have promising applications in electronics.

Development of cardanol-derived epoxidized and Si-modified pressure-sensitive adhesives (PSAs)

This research attempts to create a pressure-sensitive adhesive (PSA) from cardanol as an outset material. The two kinds of formulations were established; the first scheme followed the epoxidation of cardanol, dihydroxylation, and PSA development. In the latter system, cardanol was pretreated with dichlorodimethysilane (DCDMS) in the second scheme, continuing the same procedure to obtain PSA resin. The chemical nature and structure confirmation were done using FTIR and NMR spectroscopy, hydroxyl value, epoxy equivalent weight (EEW), etc. To evaluate PSA resin's crystallinity, thermal stability and hydrophilicity the film was separately obtained for both the schemes by curing whereas to obtain PSA tapes the obtained PSA and tackifying resins were applied onto PET sheets. XRD analysis showed a decrease in the degree of crystallinity after incorporating DCDMS. The gel content values decreased, whereas the water absorption values increased, which could be related to the increase in the hydrophilic nature of PSA with an increasing number of tacky sites. TGA and DSC showed the formation of a high amount of char yield (∼31%) and a higher Tg (−37.72 °C) in Si containing film. The probe tack, peel strength, and shear strength values were high for the formulation with equal amounts of PSA and tackifying resin. Finally, the contact angle measurements showed that the hydrophobicity of film was also improved after incorporating DCDMS. The materials resembling PSA tape and including only small amounts of tackifying resins and crosslinkers displayed the ideal characteristics with satisfactory results.

Development of tetra glycidyl epoxy-based nanocomposites and analysis of its mechanical, XRD, EDS, and physical properties for high-performance applications

This research work presents an investigation on N, N, N’, N’-tetraglycidyl-4,4′-diaminodiphenylmethane containing epoxy nanocomposites to seek out its suitability to be employed in high-performance applications. The synthesis and characterization of this epoxy denoted as ‘A’ was done. The nano reinforcement polyhedral oligomeric silsesquioxane -amine-based represented as ‘N2′ was incorporated into the synthesized epoxy. Curing of the tetraglycidyl epoxy was finished with diaminodiphenylmethane and bis (3-aminophenyl) phenyl phosphine oxide curing agents marked as X and Y respectively. The mechanical, X-ray diffraction, energy dispersive spectroscopy, viscosity, epoxy equivalent weight, and gel permeation chromatography studies were disbursed and the results thus obtained are presented.

Rapid and in-situ determination of epoxy equivalent weight of bisphenol-based epoxides by micro-Raman spectroscopy

Rapid and in-situ determination of epoxy equivalent weight of bisphenol-based epoxides by micro-Raman spectroscopy

Mechanical flexible epoxy resins with 100% bio‐based carbon content based on epoxidized vegetable oils

AbstractThis work describes the development and characterization of mechanical flexible epoxy resins based on epoxidized vegetable oils (EVO) and sebacic acid. Different oil types (linseed oil, hempseed oil, and soybean oil) with varying epoxy equivalent weight (EEW) were used. Formulation and processing parameters were systematically optimized by differential scanning calorimetry and Fourier‐transform infrared spectroscopy. The effect of the EVO type and EEW on thermo‐mechanical and mechanical properties were investigated by dynamic mechanical analysis and tensile tests at different temperatures. The EVO type had a strong effect on the thermo‐mechanical and mechanical properties of the resin. However, for the investigated commercial epoxidized linseed oils, the EEW had no effect on these properties. With epoxidized linseed oil the highest Tg and the best mechanical properties (highest tensile strength and toughness) were achieved.

Synthesis and properties of bioplastics from corn starch and citric acid-epoxidized soybean oil oligomers

Citric acid-epoxidized soybean oil oligomers (CESO) were prepared and utilized to improve the properties of corn starch-based bioplastics. CESO were synthesized by controlling the stoichiometric ratio of acid equivalent weight and epoxy equivalent weight at 3:1. Starch-based bioplastics with satisfactory properties were fabricated through solution casting. Analysis including FTIR, molecular distribution, and polydispersity index validated the ring opening polymerization of ESO and CA. The hydrogen bond and crosslinking interactions between CESO and starch were evidenced by the FTIR. SEM micrographs suggested that CESO exhibited better compatibility with starch than ESO. X-ray diffraction patterns of the bioplastics were changed apparently by CESO due to the crosslinking interaction. Swelling degree and opacity of the bioplastics reduced significantly after the introduction of CESO, while tensile strength increased remarkably from 5.62 to 6.93 MPa (p < 0.05). The bioplastic with 4 wt% CESO revealed the most comprehensive properties. Higher content of CESO (16 wt%) displayed poor interaction with starch and led to deteriorated properties of the bioplastics. The synthesized bioplastics exhibited enormous potential to partially replace petroleum-based plastics for various applications such as packaging.

Effect of reaction time on the molecular weight distribution of polyurethane modified epoxy and its properties

This paper studied the synthesis of polyurethane modified epoxy via simultaneous reaction by varying the reaction time to 30, 60, and 90 min. The polypropylene glycol and tolonate as polyurethane components were reacted simultaneously with epoxy in the presence of catalyst dibutyltin dilaurate without prepolymer polyurethane first. The effect of various reaction times on polyurethane modified epoxy (PME) properties was studied by analyzing molecular weight distribution, viscosity, epoxy equivalent weight, pot life, dry-to-touch time, elongation at break, tensile strength, and compared to the unmodified epoxy. The various reaction time processes of polyurethane-modified epoxy tend to increase the molecular weight and influence the molecular weight distribution of PME. It indicated that the reactivity polymerization of epoxy resin with polyurethane component increased with reaction time. Furthermore, these properties affect other properties, i.e., viscosity, epoxy equivalent weight, pot life, and tensile strength increase.

Utilization of Polymer Composite for Development of Sustainable Construction Material

Polymers have gained an extensive application due to their versatility of properties and benefits. Hence, the polymer blends and composites reinforced with different infusions at different scales, macro to nanofillers, can be fabricated, leading to specific tailormade applications. The main objective of this investigation is to overview the various studies carried out to reuse the waste materials like electroplating sludge, fly ash, etc. For the development of construction materials. This paper summarizes the use of polymers in composite material formulations for the development of building materials such as lightweight concrete, protective coatings, paver blocks, bricks, and structural components. Different tests, namely viscosity, density, flash point, amine value, and epoxy equivalent weight, were performed on polymers to find their suitability as binder materials. Various laboratory tests such as compressive strength, water absorption, tear resistance, flexural strength, and split tensile tests were carried out to determine the mechanical properties of the developed materials. By using polymers with the addition of sustainable filler and waste materials, the replacement of costly raw material can be achieved by more than 50% in the case of paver blocks, up to 60% in bitumen-polymer composite, 80% in case of lightweight concrete and polymer-based panels. This insight gives the framework for the selection of different materials, optimization of combining ratio of materials, and their testing for the development of polymer-based materials.

Enhancing the shelf life of epoxy monoacrylate resins using acryl phosphate as a reactive additive

Epoxy monoacrylate resins are widely used in a myriad of industrial applications; however, their shelf life still requires improvement. This work investigates the use of acryl phosphate [mixture of 2-(methacryloyloxy)ethyl phosphate and bis(2-(methacryloyloxy)ethyl) phosphate] as a reactive additive to increase the long-term storage stability of epoxy monoacrylate resins. A series of epoxy monoacrylate resins were synthesized via addition esterification reaction of diglycidylether bisphenol-A (DGEBA) with acrylic acid at different mole ratios. The epoxy equivalent weight, viscosity, and acrylation portion of the synthesized epoxy monoacrylate resin increased with increasing the acrylic acid content, and the optimization of the mole ratio of DGEBA and acrylic acid allowed obtaining a high-purity epoxy monoacrylate resin. The investigation of the storage stability of the epoxy monoacrylate resin formulated with acryl phosphate revealed that no viscosity was developed after 12 weeks, which demonstrates that the additive increased the long-term shelf life of the resin.

Physicochemical Characterization of Novel Epoxidized Vegetable Oil from Chia Seed Oil.

In this study, a novel epoxidized vegetable oil (EVO) from chia seed oil (CSO) has been obtained, with the aim to be employed in a great variety of green products related to the polymeric industry, as plasticizers and compatibilizers. Previous to the epoxidation process characterization, the fatty acid (FA) composition of CSO was analyzed using gas chromatography (GC). Epoxidation of CSO has been performed using peracetic acid formed in situ with hydrogen peroxide and acetic acid, applying sulfuric acid as catalyst. The effects of key parameters as temperature (60, 70, and 75 °C), the molar ratio of hydrogen peroxide:double bond (H2O2:DB) (0.75:1.0 and 1.50:1.0), and reaction time (0–8 h) were evaluated to obtain the highest relative oxirane oxygen yield (Yoo). The evaluation of the epoxidation process was carried out through iodine value (IV), oxirane oxygen content (Oo), epoxy equivalent weight (EEW), and selectivity (S). The main functional groups were identified by means of FTIR and 1H NMR spectroscopy. Physical properties were compared in the different assays. The study of different parameters showed that the best epoxidation conditions were carried out at 75 °C and H2O2:DB (1.50:1), obtaining an Oo value of 8.26% and an EEW of 193 (g·eq−1). These high values, even higher than those obtained for commercial epoxidized oils such as soybean or linseed oil, show the potential of the chemical modification of chia seed oil to be used in the development of biopolymers.

Synthesis characterization and application of hexafunctional epoxy resin and comparison against commercial epoxy resin

Current study compares the various analytical results of hexafunctional epoxy resins based on bisphenol-A with conventional epoxy resins. Reaction of bisphenol-A, formaldehyde, and epichlorohydrin produces hexafunctional epoxy resin. The curing properties of commercial epoxy resin and hexafunctional epoxy resin were determined using a variety of hardeners, including diethylenetriamine, triethylenetetramine, phenalkamine, polyamido amines, and polyamides. The epoxy equivalent weight (EEW), hydrolyzable chlorine content, volatile content, Brookfield viscosity, weight average molecular weight, elemental analysis (C, H, N, O analysis), and Fourier transform infrared spectroscopy were used to characterize the hexafunctional resin (FT-IR). Jute and glass reinforced composites were also prepared by using hexafunctional epoxy resins and commercial epoxy resins. Mechanical properties (tensile strength, flexural strength, Izod impact strength, and Rockwell hardness), thermal properties, and chemical resistance were determined for each composite. Hexafunctional epoxy resin-based composites exhibited superior mechanical characteristics, thermal resistance, and chemical resistance properties than commercial epoxy resin-based composites.

Novel bio-based epoxy resins from eugenol as an alternative to BPA epoxy and high throughput screening of the cured coatings

A novel vinyl ether monomer from eugenol, 2-eugenoloxyvinyl ether (EEVE), was synthesized and used as a building block for polymeric epoxy resins. The EEVE monomer was polymerized via cationic polymerization of the vinyl ether group leaving the allylic functionality of eugenol available for further epoxidation. Epoxidized poly(EEVE) resins varying in levels of epoxidation (epoxy equivalent weights from 360 to 870 g/eq) were produced and cured with twelve amine curatives at ambient and elevated temperatures for different time intervals to evaluate and optimize the curing regime. The cured coatings were screened with high throughput dye extraction and “conventional” coating testing methods and compared to coatings produced from diglycidyl ether of bisphenol-A (DGEBA). Results showed that coatings derived from epoxidized poly(EEVE) [Epoly(EEVE)] can be tuned from soft and elastic with hardness <50 GPa and glass transition temperatures (Tgs) < 20 °C to hard and brittle with hardness >500 GPa and Tgs > 60 °C by varying the extent of epoxidation and the nature of curative, whereas DGEBA resulted in hard and brittle coatings irrespective of the type of curative used in the study. Compared to DGEBA resin, coatings with similar or higher crosslink densities and hardness were obtained from Epoly(EEVE) resins with >50% epoxidation of EEVE moieties using the same curative and curing regime. These partially biobased epoxy compounds derived from eugenol have the potential to be competitive with petroleum-based DGEBA resins in coatings applications.

Kinetic study of in situ epoxidation of mustard oil

• This work explores the epoxidation and kinetics of mustard oil. • A structural study was carried out using NMR and FTIR spectroscopy. • Determined epoxy equivalent weight (EEW) for calculation of reactive groups. • Reaction rate constant calculated using maximum and minimum oxirane oxygen content. This work explores the kinetics of epoxidation of mustard oil in the presence of liquid inorganic acid catalysts by in situ generation of peroxyacetic acid. The formation of the epoxide group was studied over the reaction time for various temperatures. It was found that about 84% conversion to oxirane was achieved with significantly less oxirane cleavage by in situ epoxidation process. Peroxyacetic acid was found to be a more efficient epoxidising agent than peroxyformic acid. A structural study of epoxidised mustard oil was carried out using NMR spectroscopy as well as FTIR technique. For sulphuric acid-catalysed epoxidation of mustard oil, the rate constants ranged from 34.7 to 65. 8 × 10 −6 L mol −1 s − 1, for the temperature range of 55 to 70 °C. The activation energy was found to be 44.7 kJ mol −1 . Other associated thermodynamic parameters of change in entropy, change in enthalpy, and change in free energy of activation were calculated to be –206.8 J mol −1 K −1 , 40.2 kJ mol −1, and 109.1 kJ mol −1 , respectively.

Microcellular foaming of poly(lactic acid) branched with food‐grade chain extenders

AbstractThis study evaluated the effectiveness and efficiency of two food‐grade multifunctional epoxies chain extenders (CE) in branching PLA and improving its foamability. Both CE grades were effective in branching PLA causing increased end mixing torque, shear, elongational viscosities, molecular weight but decreased crystallinity of poly(lactic acid) (PLA) with CE content, due to chain entanglements. CE with low epoxy equivalent weight (EEW) was more efficient than the counterpart with high EEW due to its high reactivity. Neat PLA foams showed poor cell morphology with areas without nucleated cells and had a low expansion, owing to its low elongational viscosity. By contrast, there was a considerable change in the morphology of the PLA foam structure caused by its branching. Chain‐extended PLA foams had uniform cell morphology with a high void fraction (up to ~85%) and expansion ratio (an eightfold expansion over unfoamed PLA) due to their high elongational viscosities, suggesting that melt properties of branched PLA were appropriate for optimum cell growth and stabilization during foaming. Overall, CE with low EEW was the most effective grade and 0.25% the optimum content that provided appropriate melt viscosity to produce PLA foams with a homogeneous structure, fine cells, high void fraction, high volume expansion ratio, and cell‐population density.

Development of waterborne polyurethane dispersions (WPUDs) from novel cardanol-based reactive dispersing agent

The objective of the current research work is to prepare a difunctional reactive dispersing agent derived from cardanol which can be used as an alternative for dimethylol propionic acid (DMPA) in waterborne polyurethane dispersion synthesis. The novelty of the research lies between the use of bio-based resource and utilizing the sulfonic acid group as an anionic dispersible group. The cardanol was sulfonated using oleum followed by the reaction of the hydroxyl group of phenol with the epichlorohydrin (ECH). The obtained product was then hydrolyzed to generate double functionalities which can be introduced in the PU backbone through a chemical reaction with a diisocyanate. The obtained intermediates and product were characterized using hydroxyl values, epoxy equivalent weights (EEW), CHNS analysis, FTIR and 1H-NMR analysis. The typical acetone process was used for the preparation of WPUDs, and the cured films were further analyzed for the various coating properties in which thermal properties showed significant improvements with the incorporation of HESC to the PU system along with the increased char yield and glass transition temperature (Tg), whereas the mechanical properties did not show any improvements, which could be attributed to the bulky structure of HESC and increased rigidity in the polymeric network. The detailed synthesis, characterizations and obtained results are presented and discussed here.

Comparative studies on carbon fiber reinforced composites based on trifunctional epoxy resin and commercial epoxy resin

The present work focuses on comparative properties of β-naphthol based trifunctional epoxy resin and commercial epoxy resin. Reaction of β-naphthol, formaldehyde and epichlorohydrin forms trifunctional epoxy resin. β-Naphthol based trifunctional epoxy resin characterized by FT-IR, elemental analysis (C, H, N, O analyzer), epoxy equivalent weight (EEW), weight average molecular weight [Formula: see text], viscosity, rise in viscosity, hydrolysable chlorine content and volatile content. β-Naphthol based trifunctional epoxy resin cured by five different hardeners and used as matrix material for carbon reinforced composites. Composites were characterized by their mechanical properties, chemical resistance and thermal properties. Results showed excellent chemical and thermal resistance. All results were compared against commercially available epoxy resin (Diglycidyl ether of bisphenol-A based epoxy resin having EEW of 400). Results showed that β-naphthol based trifunctional epoxy resin was superior than commercial epoxy resin.

Bio-based unidirectional composite made of flax fibre and isosorbide-based epoxy resin

Abstract Ultrasound-assisted synthesis of diglycidyl ethers of isosorbide (DGEI) with different epoxy equivalent weight (EEW) with isophorone diamine (IPD) hardener have been performed. Interestingly, it was found that one specific epoxy formulation exhibits high reactivity with amine hardener inducing high glass transition and indentation stiffness. Associated with flax fibres, this new bio-based resin has made it possible to develop performing and promising unidirectional biocomposites with characteristics comparable to commercial petroleum-based epoxy resins.

Synthesis, Thermal Properties and Curing Kinetics of Hyperbranched BPA/PEG Epoxy Resin.

The hyperbranched epoxy resins (HBE) composed of bisphenol A (BPA) and polyethylene glycol (PEG) as reactants and pentaerythritol as branching point were successfully synthesized via A2 + B4 polycondensation reaction at various BPA/PEG ratios. The 13C NMR spectra revealed that the synthesized HBE mainly had a dendritic structure as confirmed by the high degree of branching (DB). The addition of PEG in the resin enhanced degree of branching (DB) (from 0.82 to 0.90), epoxy equivalent weight (EEW) (from 697 g eq−1 to 468 g eq−1) as well as curing reaction. Adding 5–10 wt.% PEG in the resin decreased the onset and peak curing temperatures and glass transition temperature; however, adding 15 wt.% PEG in the resin have increased these thermal properties due to the lowest EEW. The curing kinetics were evaluated by fitting the experimental data of the curing behavior of all resins with the Šesták–Berggren equation. The activation energy increased with the increase of PEG in the resins due to HBE’s steric hindrance, whereas the activation energy of HBE15P decreased due to a large amount of equivalent active epoxy group per mass sample. The curing behavior and thermal properties of obtained hyperbranched BPA/PEG epoxy resin would be suitable for using in electronics application.