Commercial Epoxy Research Articles

High performance epoxy resin with ultralow coefficient of thermal expansion cured by conformation-switchable multi-functional agent

Epoxy resins with low or negative thermal expansion have been widely searched for a long time owing to their great potential application in aerospace and microelectronics field. For the filler/epoxy resin composites, one key parameter of epoxy resins is to have suitable low coefficient of thermal expansion (CTE) to match with the fillers, however, it still remains a big challenge. In this work, we design and synthesize a new kind of conformation-switchable curing agent that contains dibenzocyclooctadiene (DBCOD) unit, named as cis-diamine-DBCOD. The epoxy resins cured by cis-diamine-DBCOD possess controllable CTE from negative to positive due to the conformational switch of DBCOD units, and the CTE can be tuned by the DBCOD content. We demonstrate the DBCOD units can undergo conformational change from boat to chair conformer with the rise of temperature based on the theoretical calculation and experimental results. Several commercial epoxy resins cured by cis-diamine-DBCOD also exhibit low CTE (around 10 ppm/K), reflecting the universality of the conformation-switch curing agent. Compared with conventional arylamine curing agents, the epoxy resins cured by cis-diamine-DBCOD possess higher Tg (218 °C) from DMA, which has 49 °C increase comparing with the corresponding epoxy resin with similar elongation at break. Meanwhile, the cured epoxy resin has superior mechanical properties, the tensile strength has 46.3 % increase. Therefore, the cis-diamine-DBCOD as a multi-functional conformation-switchable curing agent endows the cured epoxy resin with high dimension stability, thermal and mechanical performances for the specific applications.

Laboratory development and evaluation of an oleylamine curing Epoxy Asphalt

ABSTRACT There are still some deficiencies in the development and applications of epoxy asphalt materials, and the chemistry and curing mechanism of epoxy asphalt materials remain unknown. Based on the curing mechanism of commercial epoxy asphalt, an oleylamine curing epoxy asphalt (OCEA) material was prepared, and it was systematically described from the perspective of engineering application and reaction mechanism. The viscosity properties of OCEA were mainly used to predict its reserved time range and temperature during construction. The tensile properties of OCEA and commercial epoxy asphalt are evaluated to show the mechanical properties. The fluorescence microscopy and infrared spectroscopy of the OCEA were analyzed to understand its micromorphology and curing mechanism, and its current advantages are further explained in combination with the tensile properties of OCEA. The results show that the OCEA has the advantage of high strength and toughness. The asphalt phase can participate in the curing reaction of epoxy resin, enhancing the miscibility between constituents, which further enhances the miscibility of the asphalt binder and epoxy resin. This study can provide new materials for engineering epoxy asphalt and implications for further research on epoxy asphalt materials.

Development of Molding Compounds Based on Epoxy Resin/Aromatic Amine/Benzoxazine for High‐Temperature Electronic Packaging Applications

AbstractHeat‐resistant molding of compounds is an indispensable part in encapsulating future electronic power devices. Herein, it is used for polyfunctional epoxy resin (EP) and diamine‐phenol benzoxazine (BOZ) as resin matrix, 4,4'‐diaminodiphenylmethane (DDM) as curing agent, and iron acetylacetonate (Fe(acac)3) as curing accelerator, as well as inorganic fillers and other auxiliaries, to prepare heat‐resistant molding compounds. The curing behavior, processability and thermal performance of the EP/DDM/BOZ (EDB) resin blends containing different contents of DDM, BOZ, and Fe(acac)3 are first systematically investigated. The EDB molding compounds (MCEDB) with suitable BOZ content show good processability, and the molding process can be compatible with that of commercial epoxy molding compounds (EMC). With increasing the BOZ content, the glass transition temperature of cured MCEDB is greatly enhanced to a maximum of 261 °C determined by dynamic mechanical analyzer, owing to the hydrogen‐bond interaction generated after polymerization of BOZ increasing the rigidity of network chains. Moreover, the cured MCEDB also exhibits higher thermal decomposition stability, better high‐temperature (200 °C) mechanical properties, and lower water absorption compared to the cured EMC. After high‐temperature (200 °C) aging for 500 h, the cured MCEDB with suitable BOZ content still maintains outstanding performance. This study provides a promising strategy for preparing heat‐resistant electronic packaging molding compounds.

Boronic ester bonds crosslinked vitrimer elastomers with mechanical robustness, shape memory, self-healing and recyclability properties

Permanently cross-linked networks confer chemical and mechanical stability to cross-linked elastomers, making their recycling a serious environmental issue. Recyclable covalently crosslinked elastomers have recently been developed by building covalently adaptive networks in elastomers. Here, we demonstrate a simple and general strategy to construct covalent adaptable networks with mechanical robustness, self-healing, shape memory, and recyclability. The dynamic boronic ester linkage between silica and epoxidized natural rubber endows the material with high stretchability and high tensile strength. The boronic ester bond exchange enables the cross-linked network to achieve self-healing, remodeling, and shape memory through network structural rearrangement. The materials can be recovered by hot pressing or dissolution, and the structure of the sample recovered by dissolution remains basically unchanged. Furthermore, a self-healing flexible electronic device can be fabricated by spraying conductive graphite on the surface of these elastomers. Considering that this interfacial boronic ester bond cross-linking can be easily achieved between different commercial epoxy polymers and hydroxyl-rich nanoparticles, we believe that this work has great potential in the development of rubber-based vitrimer elastomers and flexible wearable devices.

Post-cure and γ-irradiation effects on the elastoplastic behavior of structural epoxy adhesive bulk specimens

The present work studies the effects of γ-irradiation on 3M™ Scotch-Weld™ EC-2216 B/A Gray, a commercial two-part flexible epoxy adhesive. The study aims to determine its mechanical characteristics by tensile testing bulk adhesive specimens and quantify the effect of different γ-ray doses (generated from a 60Co source) on the mechanical behavior of the adhesive. The elastoplastic stress-strain curve of the adhesive has been described until failure, varying the absorbed dose up to 500 kGy.Furthermore, a behavior evolution of the adhesive after the cure has been observed and described. The mechanical stabilization occurs between 48 and 85 days after the nominal end of the cure. It has been found that young specimens show a behaviour well described with a two-parameter power law, while for the other specimens, the Ramberg-Osgood model is more appropriate since it can also modelize their initial linear trend. A crosslinking increment can be hypothesized during this period, which could justify the overall embrittlement and stiffening of the adhesive.The adhesive, on the whole, has good mechanical stability after irradiation in the inspected interval, showing a reduction of Young’s modulus. Tensile strength and elongation at break result being quite stable with the absorbed dose, though the statistics for those parameters is poor because of the relevant quantity of invalid fractures.Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR-FTIR), Electron Paramagnetic Resonance (EPR) spectroscopy, and colorimetric analysis have also been performed to investigate the modifications induced by γ-irradiation.

Synthesis of a Curing Agent Derived from Limonene and the Study of Its Performance to Polymerize a Biobased Epoxy Resin Using the Epoxy/Thiol-Ene Photopolymerization Technique.

This study describes the synthesis of a curing agent derived from limonene as well as its application to prepare biobased thermoset polymers via the epoxy/thiol-ene photopolymerization (ETE) method. A biobased commercial epoxy resin was used to synthesize a crosslinked polymeric matrix of polyether-polythioether type. The preparation of the curing agent required two steps. First, a diamine intermediate was prepared by means of a thiol-ene coupling reaction between limonene and cysteamine hydrochloride. Second, the primary amino groups of the intermediate compound were alkylated using allyl bromide. The obtained ditertiary amine-functionalized limonene compound was purified and characterized by FTIR and NMR spectroscopies along with GC-MS. The curing agent was formulated with a tetrafunctional thiol in stoichiometric ratio, and a photoinitiator at 1 mol % concentration, as the components of a thiol-ene system (TES). Two formulations were prepared in which molar concentrations of 30 and 40 mol % of the TES were added to the epoxy resin. The kinetics of the ETE photopolymerizations were determined by means of Real-Time FTIR spectroscopy, which demonstrated high reactivity by observing photopolymerization rates in the range of 1.50–2.25 s−1 for the epoxy, double bonds and thiol groups. The obtained polymers were analyzed by thermal and thermo-mechanical techniques finding glass transition temperatures (Tg) of 60 °C and 52 °C for the polymers derived from the formulations with 30 mol % and 40 mol % of TES, respectively. Potential applications for these materials can be foreseen in the area of coatings.

Synthesis and characterisation of epoxy-functional cyclotriphosphazenes and investigation of their thermal behaviour in powder epoxy resin formulations

Epoxy-functionalized cyclotriphosphazene compounds were designed and synthesized from nucleophilic substitution reactions of hexachlorocyclotriphosphazene. The synthesized compounds were purified and their structures were characterized using spectroscopic techniques. The prepared compounds were then used as part of a commercial powder epoxy resin formulation with varying feed ratios. Thermal analysis results showed that the addition of the epoxy-functionalized phosphazenes improved the thermal stability and thus flame retardancy of the final coatings. The epoxy-functionalized phosphazene derivatives developed in this study can become a potential candidate for fire- and heat-resistant powder coating applications with more safety and performance.

Study of Water Absorption Properties of Annealed Nanodiamond/Epoxy Nanocomposites

Water absorption behavior of annealed Nanodiamond (ND) particle filled epoxy composite, has been studied. Removal of impurity present in the pristine ND and its surface modifications, were carried out by heat treatment. Different weight percent of ND (0.1, 0.3 and .05 wt. %) were incorporated in a commercial grade epoxy resin (L-12) in a controlled manner. A good and homogeneous distribution of ND in the composite, was observed. This resulted in reduction of mobility of the epoxy chain due to formation of highly immobile mono-layers around ND as well as formation of hydrogen bond between the ND and the epoxy. The water absorption and the contact angle properties of the resulting composites are measured. The results indicate that the water absorption as well as contact angle of the composite decrease with the increase of incorporated ND. It is observed that incorporation of ND into epoxy matrix, enhances the water resistance property of the composite.

The application of liquid crystalline epoxy resin for forming hybrid powder coatings

The purpose of the study was to check whether the addition of a liquid crystalline epoxy resin containing rigid mesogenic groups would have a positive effect on the properties of epoxy/polyester hybrid powder coating. The research included the preparation of three hybrid compositions of epoxy/polyester powder coating consisting of polyester resin GS 7371 with the addition of commercial bisphenol A-based epoxy resin E 011 (Composition 1), mixture of epoxy resin E 011 and liquid crystalline diepoxy resin MU22 (Composition 2) and only liquid crystalline diepoxy resin MU22 (Composition 3). By using the DSC method, the course of the cross-linking process of the prepared compositions was analyzed, and the curing conditions were selected. Based on the DSC analysis, it was also found that the addition of diepoxide MU22 reduces the glass transition temperature of the obtained coatings. For coatings cured on a steel substrate, a number of tests were carried out on the basis of which the surface structure was correlated with the chemical structure of the coatings and macroscopic surface behavior, i.e.: color, thickness, gloss, roughness, abrasion and scratch resistance, hardness, elasticity, contact angle, surface free energy, as well as adhesion to steel surface. It has been found that the modification of polyester/epoxy hybrid powder paint with liquid crystalline epoxy resin had a positive effect on its properties.

Colorimetric High-Throughput Screening Assay to Engineer Fungal Peroxygenases for the Degradation of Thermoset Composite Epoxy Resins

At present, the end-of-life management of thermoset composite epoxy resins is limited to incineration and landfill storage, highlighting the demand for the development of more sustainable measures. Due to their broad spectrum of C-H oxyfunctionalization reactions, fungal unspecific peroxygenases (UPOs) are becoming important biotechnological tools in organic synthesis while their potential use in biodegradation processes should not be underestimated. Here, we present a colorimetric screening assay aimed at engineering UPOs for the degradation of epoxy resins. We based our study on Hexflow® RTM-6, a commercial epoxy resin used extensively in the aeronautics sector. UPO mutants from the short and long families were initially benchmarked by GC/MS to determine their potential N-dealkylation activity on N,N-bis(2-hydroxypropyl)-p-toluidine (NNBT), the main structural scaffold of Hexflow® RTM-6. A reliable high-throughput colorimetric screening method was developed to quantify the lactaldehyde released by UPO attack on the tertiary amine of NNBT. Based on an evolved UPO from Psathyrella aberdarensis that was expressed by yeast, a small subset of mutant libraries with different mutational loadings was constructed and screened for NNBT N-dealkylation, thereby establishing a directed evolution platform as a vehicle to engineer UPO composite degrading variants.

Synthesis of bio-based flame-retardant epoxy co-curing agent and application in wood surface coating

A phosphaphenanthrene-containing epoxy co-curing agent (PDD) was successfully synthesized by a one-pot nucleophilic addition reaction from protocatechualdehyde (PH), 4,4′-diaminodiphenylether (DDE) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The chemical structure of the PDD was characterized with FTIR, NMR and HRMS techniques. The physical properties of the coatings containing PDD were comparable to the EP-0 (control group phosphorus content with of 0). Various loadings of PDD and 4,4′-diaminodiphenylmethane (DDM) were incorporated into commercial epoxy resin to fabricate epoxy coating on wood surface to achieve flame retardancy. The thermal stability and fire-retardant properties of epoxy coatings were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), differential scanning calorimetry (DSC) and cone calorimetry (CCT). With 1.09 wt% phosphorus content, the epoxy coating exhibited excellent flame retardancy, LOI value reached 32.6%, total heat release (THR) and total smoke release (TSP) of the EP-1.09 coated wood samples were declined by 39.8% and 61.4%, respectively. Moreover, PDD played an effective flame-retardant action both in the gas and condensed phase, not only promoting formation of continuous and dense char layer but also releasing phosphorous radicals and nonflammable gases. Hence, the bio-based co-curing agent endowed flame-retardant performance to epoxy and wood for developing functional thermosetting coating.

A Study on Biocompatible Polymer-Based Packaging of Neural Interface for Chronic Implantation.

This paper proposed and verified the use of polymer-based packaging to implement the chronic implantation of neural interfaces using a combination of a commercial thermal epoxy and a thin parylene film. The packaging’s characteristics and the performance of the vulnerable interface between the thermal epoxy layer and polyimide layer, which is mainly used for neural electrodes and an FPCB, were evaluated through in vitro, in vivo, and acceleration experiments. The performance of neural interfaces—composed of the combination of the thermal epoxy and thin parylene film deposition as encapsulation packaging—was evaluated by using signal acquisition experiments based on artificial stimulation signal transmissions through in vitro and in vivo experiments. It has been found that, when commercial thermal epoxy normally cured at room temperature was cured at higher temperatures of 45 °C and 65 °C, not only is its lifetime increased with about twice the room-temperature-based curing conditions but also an interfacial adhesion is higher with more than twice the room-temperature-based curing conditions. In addition, through in vivo experiments using rats, it was confirmed that bodily fluids did not flow into the interface between the thermal epoxy and FPCB for up to 18 months, and it was verified that the rats maintained healthy conditions without occurring an immune response in the body to the thin parylene film deposition on the packaging’s surface.

Three-Dimensional Printing and Recycling of Multifunctional Composite Material Based on Commercial Epoxy Resin and Graphene Nanoplatelet

3D printing of commercial thermosetting epoxy resin is of great significance for the rapid and low-cost construction of high-strength objects with complex structures. Meanwhile, recycling these commercial epoxy resins is essential for environmental protection and sustainable development. This paper reports direct ink writing 3D printing of a multifunctional composite material based on commercial bisphenol A epoxy resin and a 3D printing compatible technique to recycle the printed composite material. Graphene nanoplatelet is designed as an efficient functional thixotropic additive that turns the liquid epoxy resin prepolymer shear-thinning and suitable for direct ink printing. Composite materials with high resolution and high mechanical strength are printed with epoxy resin/graphene nanoplatelet inks, and they also show high thermal and electrical conductivity and fast thermo-induced shape memory response. The printed objects can be recycled by comminuting them into micropowders, which are then used as a thixotropic agent to prepare recycled DIW ink. The physical properties of the materials printed with recycled inks maintain unchanged for successive four recycling cycles. The graphene nanoplatelets at the surface of recycled comminuted powder are found to modulate the surface energy of the powder, thus making the powder able to serve as a thixotropic agent for the recycled inks. The method here provides a new solution to process commercial epoxy resin and opens a new direction to the more sustainable use of thermosetting plastics.

An Environmentally Friendly Supramolecular Glue Developed from Natural 3,4-Dihydroxybenzaldehyde.

Liquid adhesive suffers from the emission of volatile organic compounds (VOCs) that have detrimental effects on human beings. Herein, an environmentally friendly glue containing a novel supramolecule dissolved in non-toxic ethanol is developed. Poly (ether amine) (PEA) and 3,4-dihydroxybenzaldehyde (dhba) is utilized to synthesize catechol-terminated PEA, and subsequent complexation by Fe3+ results in the supramolecular component (PEA-dhba-Fe3+). The Fourier transform infrared (FTIR) spectrum together with the UV-vis spectrum reveal the existence of quinone converted from catechol. Raman spectra prove the existence of a successful complex of catechol-terminated PEA with Fe3+. The tri-complex is found to be the predominant mode and can successfully form into clusters, serving as a physical cross-linking network. The PEA-dhba-Fe3+ exhibits strong adherence to metal substrates compared to polymeric substrates, with its shear strength reaching as high as 1.36 ± 0.14 MPa when the pH of the glue is adjusted to 8. The obvious improvement of adhesion originates from the formation of interfacial coordination bonds between quinone/catechol and metal atoms, as well as their cations, as revealed by X-ray photoelectron spectroscopy (XPS) and theoretical calculations. With consideration of its merits, including strong adhesion and the minor emission of VOCs compared to commercial epoxy and acrylic adhesives, this environmentally friendly supramolecular glue has a range of cutting-edge applications as an adhesive for metal substrates.

Synthesis of TiO2 nanogel composite for highly efficient self-healing epoxy coating

IntroductionOrganic coatings are the most effective and facile methods of protecting steel against corrosion, which shields it from direct contact with oxygen and moisture. However, they are inherently defective and susceptible to damage, which allows the penetration of the corrosive media into the underlying substrates. Self-healing coatings were developed to address this shortcoming. ObjectiveThe current research aims to develop a coating with superior self-healing ability via embedment of titanium dioxide (TiO2) nanogel composite (NC) in a commercial epoxy. MethodsThe TiO2 NC was prepared by efficient dispersion of TiO2 nanoparticles in copolymer gel of acrylamide (AAm) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS) with the help of 3-(trimethoxysilyl) propyl methacrylate (MPS). The chemical structure, morphology, and thermal properties of the modified and functionalized nanoparticles were assessed by infrared spectroscopy, electron microscopy, X-ray diffraction, and thermogravimetric analysis, respectively. In addition, TiO2 nanoparticles, nano-TiO2 functionalized monomer (NTFM), and NTFM/AAm/AMPS in different weight percentages were incorporated into epoxy resin to prepare a self-healing coating. ResultsThe results confirmed the successful fabrication of the NC. In addition, the incorporation of 1 wt% NTFM/AAm/AMPS led to homogenous dispersion, enhanced anti-corrosive and self-healing performance with the healing efficiencies of 100% and 98%, which were determined by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods, respectively. ConclusionThe prepared NC was sensitive towards salt concentration, pH, which aids the quick reaction of the TiO2 NC to corrosive ions, once the cracks occur. In addition, this is a unique feature compared to the other self-healing mechanisms, especially, the encapsulation of healing agents, which can be effective as long as the healing agent is present.

Life-Cycle Analysis and Evaluation of Mechanical Properties of a Bio-Based Structural Adhesive

For this present paper, we performed a life-cycle analysis and an evaluation of the mechanical properties of an epichlorohydrin/cardanol adhesive in a neat and a nano-filled form. Six different potentials and the cost of the adhesives were derived and compared with those of a commercial epoxy resin. Overall, the neat adhesive was found to be more environmentally friendly and to have a lower production cost. However, the addition of carbon nanotubes increased both the environmental footprint and the cost. The evaluation with regards to the mechanical properties was performed through a comparison of bulk properties and joint properties with the respective average values of commonly used structural and nonstructural adhesives from the literature. It was found that for all properties except for the Young’s modulus the novel adhesive had values greater than the average values of the cosmetic adhesives and for most properties it had values close to the average values of the structural adhesives. Moreover, the presence of the carbon nanotubes enhanced the mechanical properties of the adhesive except for the tensile strength.

Influence of Air Plasma Pretreatments on Mechanical Properties in Metal-Reinforced Laminated Wood

The use of wood-based materials in building and construction is constantly increasing as environmental aspects and sustainability gain importance. For structural applications, however, there are many examples where hybrid material systems are needed to fulfil the specific mechanical requirements of the individual application. In particular, metal reinforcements are a common solution to enhance the mechanical properties of a wooden structural element. Metal-reinforced wood components further help to reduce cross-sectional sizes of load-bearing structures, improve the attachment of masonry or other materials, enhance the seismic safety and tremor dissipation capacity, as well as the durability of the structural elements in highly humid environments and under high permanent mechanical load. A critical factor to achieve these benefits, however, is the mechanical joint between the different material classes, namely the wood and metal parts. Currently, this joint is formed using epoxy or polyurethane (PU) adhesives, the former yielding highest mechanical strengths, whereas the latter presents a compromise between mechanical and economical constraints. Regarding sustainability and economic viability, the utilization of different adhesive systems would be preferable, whereas mechanical stabilities yielded for metal-wood joints do not permit for the use of other common adhesive systems in such structural applications. This study extends previous research on the use of non-thermal air plasma pretreatments for the formation of wood-metal joints. The plasma treatments of Norway spruce [Picea abies (L.) Karst.] wood and anodized (E6/EV1) aluminum AlMgSi0.5 (6060) F22 were optimized, using water contact angle measurements to determine the effect and homogeneity of plasma treatments. The adhesive bond strengths of plasma-pretreated and untreated specimens were tested with commercial 2-component epoxy, PU, melamine-urea formaldehyde (MUF), polyvinyl acetate (PVAc), and construction adhesive glue systems. The influence of plasma treatments on the mechanical performance of the compounds was evaluated for one selected glue system via bending strength tests. The impact of the hybrid interface between metal and wood was isolated for the tests by using five-layer laminates from three wood lamellae enclosing two aluminum plates, thereby excluding the influence of congeneric wood-wood bonds. The effect of the plasma treatments is discussed based on the chemical and physical modifications of the substrates and the respective interaction mechanisms with the glue systems.

Real-Time Monitoring Polymerization Reactions Using Dipolar Echoes in 1H Time Domain NMR at a Low Magnetic Field.

1H time domain nuclear magnetic resonance (1H TD-NMR) at a low magnetic field becomes a powerful technique for the structure and dynamics characterization of soft organic materials. This relies mostly on the method sensitivity to the 1H-1H magnetic dipolar couplings, which depend on the molecular orientation with respect to the applied magnetic field. On the other hand, the good sensitivity of the 1H detection makes it possible to monitor real time processes that modify the dipolar coupling as a result of changes in the molecular mobility. In this regard, the so-called dipolar echoes technique can increase the sensitivity and accuracy of the real-time monitoring. In this article we evaluate the performance of commonly used 1H TD-NMR dipolar echo methods for probing polymerization reactions. As a proof of principle, we monitor the cure of a commercial epoxy resin, using techniques such as mixed-Magic Sandwich Echo (MSE), Rhim Kessemeier—Radiofrequency Optimized Solid Echo (RK-ROSE) and Dipolar Filtered Magic Sandwich Echo (DF-MSE). Applying a reaction kinetic model that supposes simultaneous autocatalytic and noncatalytic reaction pathways, we show the analysis to obtain the rate and activation energy for the epoxy curing reaction using the NMR data. The results obtained using the different NMR methods are in good agreement among them and also results reported in the literature for similar samples. This demonstrates that any of these dipolar echo pulse sequences can be efficiently used for monitoring and characterizing this type of reaction. Nonetheless, the DF-MSE method showed intrinsic advantages, such as easier data handling and processing, and seems to be the method of choice for monitoring this type of reaction. In general, the procedure is suitable for characterizing reactions involving the formation of solid products from liquid reagents, with some adaptations concerning the reaction model.

Improving Surface Functionality, Hydrophilicity, and Interfacial Adhesion Properties of High-Density Polyethylene with Activated Peroxides.

Polyolefins have had limited application in advanced technologies due to their low surface energy, hydrophobicity, and weak interfacial adhesion with polar coatings. Herein, we propose the use of transition metals at their lowest oxidation state and inorganic peroxides to improve the functionality, surface free energy, hydrophilicity, and adhesion properties of high-density polyethylene (HDPE). Among the nine combinations of transition metals and peroxides used in this study, the combination of Co(II) and peroxymonosulfate (PMS) peroxide was the most effective for surface modification of HDPE, followed closely by the combination of Ru(III) and PMS. After chemical treatment, HDPE's surface functionality, composition, and energy were analyzed via Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements. Hydroxyl, carbonyl, and carboxylic acid functional groups were detected on the surface, which explained the improved hydrophilicity of the modified HDPE surface; the contact angle of HDPE with DI water decreased from 94.31 to 51.95° after surface treatment. To investigate the effect of HDPE's surface functionality on its interfacial properties, its adhesion to a commercial epoxy coating was measured via pull-off strength test according to ASTM D54541. After only 20 min of surface treatment with Co(II)/PMS solution, the adhesion strength at the interface of HDPE and the epoxy coating increased by 193%, confirming the importance of polyolefins' surface functionality on their interfacial adhesion properties. The method outlined herein can improve HDPE's surface functionality by introducing sulfate radicals. It improves HDPE's hydrophilicity and adhesion properties without requiring strong acids or time-consuming pre- or post-treatment processes. This process has the potential to increase the use of polyolefins in various industries, such as for protective coatings, high performance lithium-ion battery separators, and acoustic sensors.

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.