Epoxy Hardener Research Articles

Quantification of anhydride groups in anhydride-based epoxy hardeners by reaction headspace gas chromatography.

We demonstrate a reaction headspace gas chromatographic method for quantifying anhydride groups in anhydride-based epoxy hardeners. In this method, the conversion process of anhydride groups can be realized by two steps. In the first step, anhydride groups in anhydride-based epoxy hardeners completely reacted with water to form carboxyl groups. In the second step, the carboxyl groups reacted with sodium bicarbonate solution in a closed sample vial. After the complete reaction between the carboxyl groups and sodium bicarbonate, the CO2 formed from this reaction was then measured by headspace gas chromatography. The data showed that the reaction in the closed headspace vial can be completed in 15min at 55°C, the relative standard deviation of the reaction headspace gas chromatography method in the precision test was less than 3.94%, the relative differences between the new method and a reference method were no more than 9.38%. The present reaction method is automated, efficient and can be a reliable tool for quantifying the anhydride groups in anhydride-based epoxy hardeners and related research.

Heat-induced bubble expansion as a route to increase the porosity of foam-templated bio-based macroporous polymers

Macroporous polymers were prepared by mechanically frothing a bio-based epoxy resin and hardener mixture to first create air-in-resin liquid foams, followed by curing of these liquid foams. It was found that heating the air-in-resin liquid foams prior to their gelation decreased the viscosity of the resin mixture and increased the pressure of the air bubbles, leading to an isotropic expansion of the air bubbles. This resulted in an increase in the porosity of the resulting foam-templated macroporous polymers from 71% to 85%. Correspondingly, the compressive moduli (E) and strengths (σ) of the foam-templated macroporous polymers decreased from 231 MPa and 5.9 MPa, respectively, to 58 MPa and 1.9 MPa, respectively. This decrease is attributed to an increase in the porosity and pore throat frequency of the foam-templated macroporous polymers when heat was applied to the liquid foams. The deformation of the pores based on in situ SEM micro-compression test of the fabricated foam-templated macroporous polymers is also discussed.

Mesoporous silica as amine immobiliser for endowing healing functionality to epoxy resin

Abstract Feasibility of physical entrapment approach towards the immobilisation of amine hardener in mesoporous silica has been demonstrated for potential applications in the perspective of self-healing. A representative mesoporous silica (SBA-15) was synthesised using polymer-templated technique and employed as a substrate for immobilizing triethylene tetramine, a conventional epoxy hardener. Polymeric composites containing microencapsulated epoxy microcapsules and amine loaded SBA-15 were prepared by room temperature curing. The autocatalytic nature associated with the curing of epoxy remained unaltered due to introduction of either SBA-15 or epoxy loaded microcapsules, as confirmed by calorimetric studies. Healing efficiency, as quantified in terms of the ratio of impact strength before and after healing, was found to increase proportionally with increasing loading of healing additives in the formulation, with complete healing (100%) being exhibited at 20% microcapsule loading.

Comparative Study of Sound Absorption Coefficients of Coir/Kenaf/Sugarcane Bagasse Fiber Reinforced Epoxy Composites

This research focuses on the sound absorption coefficient of three different natural fibers reinforced epoxy composites. The natural fibers used are coconut coir, kenaf, and sugarcane bagasse. All of these fibers were mixed with epoxy resin and hardener with a ratio of 4:1. The mixtures were then poured into a circular mold and compressed by using compression molding technique. It was left for curing for 24 hours at standard room temperature. The results were obtained using the two-microphone transfer functions impedance tube method according to ASTM E1050-12. It is found that as the fiber loading increased, the sound absorption coefficient of the composites increased. 20wt% Coconut coir epoxy composites and 20wt% kenaf fiber epoxy composites have the highest sound absorption coefficient with almost similar sound absorption of 0.078 at 5000Hz. While, 20wt% sugarcane bagasse epoxy composites have sound absorption of 0.075 at 5000Hz.

Multi-scale modelling of carbon nanotube reinforced crosslinked interfaces

In this paper, we study the crosslinking route and interfacial interactions for achieving superior properties in carbon nanotube (CNT)-reinforced epoxy-based nanocomposites by using multi-scale modelling. For that purpose, polymeric epoxy matrices consisting of EPON 862 epoxy and TETA hardener molecules were coarse-grained and simulated using the dissipative particle dynamics (DPD) method. Furthermore, CNTs were coarse-grained as rigid rods and embedded into the uncrosslinked mesoscopic polymer system. Reverse-mapping of the atomistic details onto the coarse-grained models was carried out to allow further simulations at the atomistic scale using molecular dynamics (MD) while keeping the periodicity of the CNTs’ structure. The mechanism of crosslinking was simulated, and both neat and CNT-reinforced thermoset nanocomposites with different degrees of crosslinking were reconstructed. Normal stresses in both tensile and compressive loading directions (up to 0.2% strain) were calculated, and the yield strength (at 0.2% offset) and compressive/elastic modulus in both normal directions are reported, which match well with experimental values. Overall, this paper explores a fast and straightforward procedure to bridge periodic mesoscopic structures, such as CNTs and their nanocomposites, to experimentally tested material properties.

A preliminary evaluation of bio-based epoxy resin hardeners for maritime application

A screening of different hardeners derived from cashew nut shell liquid (CNSL) was performed; they were compared to a conventional hardener in an epoxy resin system for composite production by infusion process. All samples were submitted to different post-curing processes before tensile strength and moisture uptake were evaluated. It was observed that the use of CNSL hardeners produced cured epoxies similar in Young’s Modulus (YM) to the conventional hardener with a lower moisture uptake however, the hardeners resulting in a low YM had a marked reduction in moisture uptake. Studies of the post-curing process showed that the moisture uptake of the conventional system can be improved but, depending on the temperature applied, the process can be detrimental to the CNSL hardeners, provided that moisture uptake was increased after post-curing. The results indicate that biobased content can be introduced to a conventional epoxy resin system by replacing the conventional hardener commonly used by a sustainable one derived from cashew nut shell liquid with an additional moisture uptake reduction.

Silane Modification of the Flax/Epoxy System Interface

Natural fibres (NF) are normally subjected to pre-treatment to ensure good fibre to matrix bonding and consequent mechanical properties and durability. To enhance the sustainability of NF composite systems, it would be sensible to minimise processes that incur environmental burdens. This research considers that addition of silane coupling agent to epoxy resin hardener may be an alternative to the direct chemical pre-treatment of NF before composites manufacture. The current study indicates that silane-in-hardener can eliminate the pre-treatment of fibres and generates composites with optimum mechanical properties.

Ballistic impact response of Kevlar Composites with filled epoxy matrix

Impact resistance and weight are important features for ballistic materials. Kevlar fibres are the most widely reinforcement for military and civil systems due to its excellent impact resistance and high strength-to-weight ratio. Kevlar fibres or spectra fiber composites are used for designing personal body armour to avoid perforation. In this study, the ballistic impact behaviour of Kevlar/filled epoxy matrix is investigated. Three different fillers, nanoclay, nanocalcite and nanocarbon, were used in order to increase the ballistic impact performance of Kevlar-epoxy composite at lower weight. The filler, nanoclay and nanocalcite, content employed was 1 wt.% and 2 of the epoxy resin–hardener mixture while the nanocarbon were dispersed into the epoxy system in a 0.5%, 1% and 2% ratio in weight relating to the epoxy matrix. Specimens were produced by a hand lay-up process. The results obtained from ballistic impact experiments were discussed in terms of damage and perforation. The experimental tests revealed a number of damage mechanisms for composite laminated plates. In the ballistic impact test, it was observed whether the target was perforated completely penetrated at the back or not. The presence of small amounts of nanoclay and nanocalcite dispersed into the epoxy system improved the impact properties of the Kevlar/epoxy composites. The laminates manufactured with epoxy resin filled by 1 wt.% of nanoclay and 2 wt% nanocalcite showed the best performance in terms of ballistic performance. The addition of nanocarbon reduced ballistic performance of Kevlar-epoxy composites when compared the results obtained for laminates with 0% nanoparticles concentration.

Quantification of the amine value in aliphatic amine epoxy hardeners by using a reaction-based headspace gas chromatographic technique

This work investigates a reaction-based and solvent-assisted HS-GC method for the determination of the amine value in aliphatic amine epoxy hardeners.

Effect of Nanoparticles on Wettability of Nanocoating on Carbon Steel

Nanocoatings plays an important role in coating industry. The solution was being prepared through copolymerization of epoxy resin hardener and with the incorporation of metal oxide nanoparticles, Zinc Oxide (ZnO) and Silica (SiO2). ZnO and SiO2 were synthesized using sol-gel. Epoxy hardener acted as host while the metal oxide nanoparticles as guest components. The formulation of nanocoatings with excellent adhesion strength and corrosion protection of carbon steel was studied. The performance of wetting ability with different medium was analysed using contact angle. Water medium showed the addition of 3wt% of hybrid between ZnO and SiO2 was the best nanocoating to form hydrophobic surface and was also the best nanocoating surface to form hydrophilic surface with vacuum oil dropping. In oil dropping, the contact angle was smaller than 90° and the water drop tends to spreads on surface.

STUDI PENGARUH PROSES MANUFAKTUR KOMPOSIT BERMATRIK EPOKSI TERHADAP KEKUATAN TARIK DAN IMPAK PADA KOMPOSIT HYBRID BERPENGUAT SERBUK KAYU ALBASIA DAN SERAT GELAS

A composite material is very efficient to use at a structure which needs a combination between strength and stiffness and light weight. The advantage of composite material compared to a metal is corrosion resistance, accessible, and reasonable price. This study aims to determine the tensile and impact strength composites of the epoxy matrix composite reinforced by glass fiber and albsia sawdust. The composites were made using variations of stirring time 15 minutes and 30 minutes with a stirring speed of 658 rpm and 858 rpm. The composite were made using variations of the drying temperatures 40ºC, 50ºC, 60ºC, 70ºC, and the room temperature. The reinforced materials is used albasia sawdust and woven glass fiber. The matrix was Epoxy Resin Bakelite EPR 174 and Epoxy Hardener V-140. The methodology for making the composite test specimens particles was hand lay-up (open mold). The highest tensile strength testing on a composite was 37.92 MPa with a stirring time of 30 minutes and 858 rpm stirring rotation. For the impact testing, the highest visible impact at 0.0024 J/mm² in the composite with a stirring time of 15 minutes and 858 rpm stirring rotation. Through this test, it was obtained the highest tensile strength of 43.03 MPa in the composite with 50ºC drying temperature variation. Meanwhile, the composites with 60ºC drying temperature variation had the highest impact strength with a value of 0.0037 J/mm². The composite material composition and morphology of the fracture were analyzed by SEM observation.

Strengthening of a RC Beam using Synthetic FRP Laminates

Objectives: The present research paper summarizes the study of use of synthetic polyester fiber for the strengthening of the reinforced concrete beams. Methods: In this experimental study, ten reinforced concrete beams were casted. They were externally strengthened with the help of synthetic polyester fiber using epoxy resin and hardener. The application of Polyester Fibre Reinforced Polymer sheets for strengthening of RC beams was done in u-wrap and bottom wrap. The effect of this on ultimate load carrying capacity and flexural strength was examined. Findings: The reinforced concrete beams were tested to failure using symmetrical two point concentrated static loading system. The results were found experimentally on load, deflection and failure types of each of the beams. The effect of various positions of wrapping of Polyester Fiber Reinforced Polymer on ultimate load carrying capacity was investigated. The results obtained showed increase in the ultimate load carrying capacity and flexural strength of the beams as compared with the control beam. The ultimate load obtained with polyester fibre reinforced beam was, however less compared to Carbon/Glass/Aramid as recorded in the literature. But the results obtained were encouraging and useful. Applications: Defects occur in reinforced concrete due to many factors like-age, corrosion of steel reinforcement, defective structural design etc. Fibre reinforced polymers can be successfully utilized for rehabilitation of these RC structures.

Epoxy Resin Thermosets Derived from Trehalose and β-Cyclodextrin

Epoxy resins are ubiquitous in high-performance composite applications because of their excellent mechanical strength, thermal and chemical resistance, strong adhesion, and low shrinkage after curing. Bio-based epoxy resins derived from natural products such as carbohydrates offer tremendous potential for creating new polymeric materials. Sugars and their derivatives often offer great biodegradability and functionality such as the presence of multiple hydroxyl groups that impart highly cross-linked polymer networks. Moreover, their ring structures can afford polymers with high glass transition temperatures. To develop epoxy resins containing sustainably sourced feedstocks, we designed and synthesized trehalose- and β-cyclodextrin-based carboxylic acid hardeners for epoxy resins and examined the thermal, mechanical, and adhesive properties of the resulting materials. Trehalose and β-cyclodextrin were succinylated with excess succinic anhydride, and the resulting carboxylic acid hardeners formed homogeneous...

Self-healing glass fiber/epoxy composites with polypropylene tubes containing self-pressurized epoxy and mercaptan healing agents

To improve flowability of the healing agent released from micropipelines without manual intervention, this work prepared a proof-of-concept self-healing glass fiber/epoxy composite, in which plastic (polypropylene (PP)) tubes were embedded and used as containers of epoxy/mercaptan healing agent and foaming agent. Decomposition of the foaming agent at 70 °C created inflated gas in the sealed PP tubes in advance, which increased the internal pressure. Upon damage of the composite, the pressurized healing fluid burst out covering larger cracked plane and enhanced mixing of the liberated epoxy monomer and hardener. As a result, higher healing efficiency was observed as compared to the case without pressurization. The factors that influence healing performance of the system (e.g., tube spacing, content of the foaming agent, foaming time, etc.) were discussed in detail. The proposed approach is believed to have adequate expansibility and can be applied in other self-healing composites with micropipelines.

Self-healing of nanofiber-based composites in the course of stretching

Abstract Here we aim to elucidate the self-healing mechanisms in composites with embedded solution-blown nanofibers containing separate reservoirs of epoxy resin and hardener in their cores. In tensile tests of such composite materials with the resin- and hardener-containing solution-blown nanofibers embedded in a polymer matrix, it is shown that the fibers can be ruptured by stretching, thereby releasing the epoxy resin and hardener. Given a resting (or holding) period of 1–2 h, such materials can experience a restoration or even enhancement of stiffness in subsequent stretching, thereby displaying self-healing properties. In two model macroscopic experiments with a single crack tip, conducted in the Appendix with the aim to elucidate the self-healing mechanism, the epoxy resin and hardener released into the tip are shown to react with each other, resulting in a cured and hardened epoxy that heals the crack tip.

Preparation of waterborne P-N containing epoxy resin curing and its performances

Purpose The flammability of epoxy resin is a major disadvantage in applications that require flame resistance. Epoxy monomers and hardeners containing flame-retardant elements are molecularly incorporated in the resin network are expected to exhibit better flame resistance than those borne on an additive approach. In recent years, because of health and environmental regulation, the use of waterborne coatings has received many attentions. However, waterborne epoxy resin curing agent with excellent flame retardancy has been seldom reported. The paper aims to study the preparation of waterborne P-N-containing epoxy resin curing agent and its performances (P-N – phosphorous and nitrogen). Design/methodology/approach Waterborne P-N-containing epoxy curing agent was prepared in this study using reactive flame retardant 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-xa-10-phosphaphenanthrene-10-oxide, liquid epoxy resin, triethylenetetramine and butyl glycidyl ether at the mole ratio of 1.0:2.0:2.0:2.0. Findings The results show that the epoxy thermoset from the prepared P-N-containing curing agent presents good flame retardancy and can pass the V-1 rating, and the cured epoxy thermoset film presents excellent performances such as water resistance, adhesion, impact resistance and pencil hardness. This study provides useful suggestions for the application of the water-borne flame retardancy epoxy resins in coating industry. Research limitations/implications Each step of products during the preparation of waterborne P-N-containing epoxy curing agent cannot be accurately tested. Originality/value This method for synthesis of waterborne P-N-containing epoxy curing agent is novel and could be used for various applications in epoxy coating industry.

Structure of Polymer Composites on Basis of Epoxy Resin and Organic and Inorganic Dispersed Industrial Wastes

he paper presents the influence of the conditions of combining of the epoxy binders and particulate filler on the formation of submolecular structure of the composites. The optimum concentrations of filler among industrial waste in the composition content has been determined and the dependence of the formation of the structure of the following technological parameters such as filler concentration, order of components combining (epoxy resin, hardener and filler), solidification modes of the composition has been identified. Microphotographs of the structure and interpretation of the connection of the properties of the composites and their structure are presented below.

Occupational contact dermatitis caused by 1,3-benzenedimethanamine, N-(2-phenylethyl) derivatives in hardeners for epoxy paints and coatings.

Amines in epoxy hardeners are significant causes of occupational allergic contact dermatitis among workers who use epoxy resin systems. To describe a novel group of contact allergens: N-(2-phenylethyl) derivatives of the reactive amine 1,3-benzenedimethanamine (1,3-BDMA). We describe the clinical examinations and exposure of 6 patients with occupational contact allergy to derivatives of 1,3-BDMA. Of the 6 patients, 4 were spray painters who used epoxy paints, 1 was a floor layer who handled a variety of epoxy coatings, and 1 was a worker in epoxy hardener manufacture. We were able to confirm exposure to epoxy hardeners that contained derivatives of 1,3-BDMA in 5 of the 6 sensitized patients. Despite the close structural resemblance between derivatives of 1,3-BDMA and m-xylylenediamine (MXDA), only 3 patients reacted positively to MXDA. Concomitant contact allergy to diglycidyl ether of bisphenol A resin was seen in 2 of the 6 patients. Because of the lack of a commercially available patch test substance, the diagnosis of contact allergy to derivatives of 1,3-BDMA requires patch testing with either the epoxy hardener product or a hardener ingredient that contains the derivatives of 1,3-BDMA.

The system of carbon fibre-reinforced plastics micro-tubes for self-healing of glass fibre-reinforced plastics laminates

A system of pultruded carbon fibre-reinforced plastics micro-tubes is used for self-healing simulation in laminated polymer composite. The system consists of a package of micro-tubes, placed in the symmetry plane of the GFR/epoxy laminate stack. Healing agent is a mixture of the epoxy resin and hardener. The healing agent releases and penetrates into the cracks after the composite is damaged by the quasi-static indentation. The specimens are healed at 30℃ for 24 h. Rectangular specimens notched under ASTM D2733 have been subjected to tensile test to determine interlaminar shear strength. Shear strength of specimens has been compared in three states (virgin, damaged and healed) for various ways of healing. After the most effective self-healing, the interlaminar shear strength has been recovered to 70 ± 15% of those for virgin specimens that almost twice exceeds the residual strength of the damaged specimens.

Simulation of stress in an innovative combination of composite with metal sheet

In this article research of stress impact in multi-point connection glass epoxy composite with a metal sheet with a rivet nuts was presented. Composite materials are increasingly used because of the good mechanical properties and low price. The laminates are composites of a layer structure, characterized by very high strength in the direction of the fibers, their weakness is not good toughness in a direction perpendicular to the layers. Mainly checking of displacements and stresses generated on the sheet as a result of pneumatic actuators load for composite boards was carried out. Glass-epoxy composite consisting of four layers of glass mat with a weight of 1000 g/m2 and an epoxy resin and hardener HG700 LG700 volume ratio of 38/100 was created. Next composite was fixed with steel plate with a rivet nuts and bolts. A model of laminate samples and plate was simulate in Siemens NX 8.5 software. The simulation results will determine stresses and displacements in conjunction newly designed composite sheet. Strength analysis was performed with the use of the module NX Advanced Simulation. FEM is an advanced method for solving systems of differential equations, based on the division of the field into finite elements for which the solution is approximated by specific functions, and performing the actual calculations only for nodes of this division. Due to the complexity of the created object to simplify the elements made to reduce the calculation time. This article presents the study of stresses and displacements in the composite plates joined with sheet metal, in summary of this article, the authors compare the obtainted results with the computer simulation results in the article: " The study of fix composite panel and steel plates on testing stand".