Epoxy Samples Research Articles

Improvement in mechanical and thermal properties of epoxy hybrid composites by functionalized graphene and carbon-nanotubes

Thermo-mechanical properties of amine functionalized multi-layered graphene (Af-MLG) and amine functionalized multi walled carbon nanotube (Af-MWCNT) epoxy hybrid composites is investigated. Ratio of hybrid fillers is being kept as 1:1 with a variation in wt% from 0.25 to 2.0. An optimum dispersion of hybrid nanofillers in epoxy matrix environment by using a probe sonicator has confirmed through TEM images. The presence of amine group in their corresponding composites (Af-M(Gr:CNT)/Ep-C) is confirmed through Fourier transform Infrared spectroscopy (FTIR), while amorphous nature of composite has been substantiate by using X-ray diffraction (XRD). Scanning electron microscope and transmission electron microscopy (SEM) images of Af-M (Gr: CNT)/Ep-C shows interaction between graphene sheet and MWCNT. Thermal decomposition temperatures of composites are investigated by using thermo-gravimetric analysis (TGA). A maximum increase of 52.8% in tensile strength for composites with 0.5 wt% loading of hybrid fillers shows collegial effects of both fillers when used in combination. Composites with 1.0 wt% loading of hybrid fillers demonstrate the highest flexural strength and thermal properties (degree of degradation of composites) as compared to the neat epoxy samples.

Thermo-mechanical properties of epoxy nanocomposites incorporating amino acid and acid functionalized multi-walled carbon nanotubes

In this study, multi-walled carbon nanotubes (MWCNTs) were functionalized by both sulfuric/nitric acids and amino acids to form COOH and NH2/COOH/OH groups on their surface, respectively. The functionalized MWCNTs were characterized by Fourier Transform Infrared Spectroscopy, titration test, thermal gravimetric analysis, and solvent stability test. The results revealed that in each method, the functional groups were successfully attached to the surface of nanotubes. Acid treatment grafted more oxygen-containing groups compared to commercial carboxylated MWCNTs. The amino acid functionalized MWCNTs indicated improved stability in different solvents compared to raw and acid treated MWCNTs. These functionalized MWCNTs were incorporated into epoxy resin and the properties of the nanocomposites were evaluated by scanning electron microscopy, tensile test, dynamic mechanical thermal analysis, differential scanning calorimetry, and thermogravimetric analysis. The morphology of the nanocomposites revealed that acid and amino acid treated samples had better interaction with the epoxy resin. Compared to epoxy sample contained raw MWCNT (control) and commercial carboxylated MWCNTs, the addition of functionalized MWCNTs to the epoxy resin improved the tensile strength by 39% and 25% (for acid treated) and 46% and 33% (for amino acid treated), respectively. The best tensile properties for acid and amino acid treated samples were reached by MWCNTs acid treated at 110℃ for 15 min and MWCNTs treated in a 50 g/L aqueous solution of amino acid, respectively. Storage modulus of the epoxy samples which contained acid and amino acid treated MWCNTs were 1560 and 1900 MPa, respectively. The glass rubber transition temperature ( Tg) of the epoxy samples containing acid and amino acid treated nanotubes were increased by 1.1℃ and 5.9℃, respectively, compared to the control sample. Therefore, based on these mechanical properties, the epoxy samples containing nanotubes functionalized by amino acid exhibited the highest performance in the epoxy nanocomposite. Incorporating acid and amino acid treated MWCNTs accelerated the curing process of epoxy where the curing temperature decreased by 9.1℃ and 13.3℃, respectively. Because of the reaction between amine groups grafted on MWCNTs in the amino acid treatment and epoxide groups of the epoxy resin, this acceleration was more significant in the case of amino acid sample. Note that addition of functionalized MWCNTs to epoxy resin did not lead to increased thermal stability.

Investigation of mechanical properties of graphene decorated with graphene quantum dot‐reinforced epoxy nanocomposite

ABSTRACTIn this investigation, the mechanical properties such as compression, impact, and flexural properties of graphene decorated with graphene quantum dots (GDGQD) epoxy composites with concentration of GDGQD ranging from 0.25 to 1 wt % were studied. Ideal mechanical properties are obtained by systematically varying the filler weight in the epoxy matrix. The morphological studies of GDGQD have been characterized using transmission electron microscope, X‐ray diffraction, and Fourier transform infrared technique. The compression, impact, and flexural strengths were enhanced effectively by the GDGQD loading. With the addition of 0.75 wt % of GDGQD, the compressive strength, compressive modulus, flexural strength, and flexural modulus of the composites were improved by 22, 29, 31, and 63%, respectively. Also an improvement in impact strength of 102% for 0.75 wt % GDGQD epoxy sample was also obtained. Examination of fractured test specimens was performed with scanning electron microscope. The enhancement in the mechanical properties is due to the better stress transfer that is attributed by enhanced interfacial bonding between GDGQDs and the epoxy. Using the GDGQD aspect ratio in the two‐dimensional randomly oriented filler modified Halpin–Tsai model, the theoretical flexural modulus for the GDGQD/epoxy composites has been established. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48680.

Influence of ambient conditions on electrical partial discharge resistance of epoxy anhydride based polymers using IEC 60343 method

Epoxy resins are the most used polymeric systems when it comes to high voltage insulations. Their excellent electrical and mechanical properties in combination with the ability to withstand high thermal stress are what makes them so appreciated. During usage, partial discharges (PD) can occur in high voltage machines, e.g., generators or electric motors. They may deteriorate the insulation system. To prevent machine failures of high voltage machines and to guarantee longer operating times, it is important to know the influencing factors of PD. This study deals with the evaluation of the influencing factors of partial discharge and makes an effort to assess the partial discharge resistance (PDR) of bisphenol-A epoxy resin. Neat epoxy samples and samples loaded with SiO 2 -nanoparticles are prepared and submitted to partial discharge under different atmospheres using a method similar to the IEC 60343. After electrical aging, the specific eroded volume of the polymers is measured via a non contact surface metrology system. The determining factors of the partial discharge resistance were identified. Using SiO 2 — nanoparticles, an improvement of the chemical resistance, which has decisive influence on the partial discharge resistance, was found.

Microencapsulation of quinoline and cerium based inhibitors for smart coating application: Anti-corrosion, morphology and adhesion study

In this study, linseed oil-filled urea-formaldehyde-based microcapsules containing cerium acetate (Ce) and 8-Hydroxyquinoleine (8-HQ) were synthesized in an oil-in-water emulsion via in-situ polymerization method. The Field Emission Scanning Electron Microscopy (FE-SEM) and Optical Microscopy (OM) were used to study the shape and morphology of the prepared microcapsule. The results revealed the regular spherical capsules with 20–120 μm diameters. Prepared microcapsules were dispersed in the epoxy matrix in single (Ce and 8-HQ) and mixed (50 wt.% Ce +50 wt.% 8-HQ) forms. Electrochemical Impedance Spectroscopy (EIS) and standard salt spray test were conducted to study anti-corrosion properties of different epoxy-based samples on the mild steel substrate. The results revealed improved anti-corrosion and healing performance of microcapsule embedded coating samples compared with their blank counterparts during 28 days exposure to the salt spray test conditions. The sample containing mixed form microcapsules showed the best performance among all samples. After one-week immersion in 3.5 wt.% NaCl electrolyte, |Z| at low-frequency value (|Z|lf) for neat epoxy, 8-HQ, Ce and mixed forms samples decreased from 2.81 × 108, 2.70 × 109, 1.02 × 109 and 8.62 × 109 to 1.22 × 104, 2.69 × 108, 3.40 × 107 and 1.98 × 109 (ohm. cm2), respectively. Finally, fluorescence microscopic study showed that the 8-HQ compound was released at the damaged area on the coated substrate and detects the corrosion phenomenon at the early stage as a smart corrosion indicator.

Enhancement of thermal and mechanical properties of novel micro-wear debris reinforced epoxy composites

Handling of machining waste called wear debris is a great challenge to the manufacturing industries. Effective ways of managing wear debris is essential for a clean and green environment. This work addresses an effective method of utilization of machining wear debris in the fabrication of polymer composites and the effect of wear debris reinforcement on the thermal and mechanical properties of the epoxy composites are investigated. After the machining process, the residue called wear debris from Wire-cut Electrical Discharge Machine (WEDM) is collected and used as a reinforcement. The micro-composites are fabricated in three different filler concentrations (i.e., 2 wt%, 4 wt%, and 6 wt% of WEDM micro-particles) and their performances are compared with pure epoxy sample. The ThermoGravimetric Analysis (TGA) on the reinforced epoxy samples showed enhanced thermal stability than pure epoxy sample. The Differential Scanning Calorimeter (DSC) and Laser Flash Apparatus were used to assess the specific heat and thermal diffusivity of the epoxy and its composites respectively. The 6 wt% WEDM microparticles reinforced epoxy composite showed 87.25% of improvement in thermal conductivity than pure epoxy. This enhancement in thermal conductivity of the epoxy composites resulted in improved heat transfer, thus making them good candidate for Printed Circuit Board (PCB) and microelectronics applications. In addition, reinforced epoxy samples showed significant improvement in tensile and flexural strengths when compared to pure epoxy samples. Field Emission Scanning Electron Microscopy (FE-SEM) equipped with EDS was used to analyse the fractured surfaces and the presence of various chemical elements in WEDM microparticles. The particle size analysis showed the size distribution of WEDM microparticles and the avg. size of WEDM microparticles measured was 0.257 μm.

Investigation on the anticorrosion, adhesion and mechanical performance of epoxy nanocomposite coatings containing epoxy-silane treated nano-MoO3 on mild steel

The effect of introducing MoO3 (Molybdenum oxide) nanoparticle in the epoxy coating was analyzed by EIS and SECM methods in natural seawater. The aminopropyl triethoxy silane (APTES) was treated with the nanoparticle for the proper dispersion and chemical interaction of nanoparticle with the epoxy resin. The introduction of MoO3 nanoparticle in the epoxy coating enhances the charge transfer resistance (Rct) as well as the film resistance (Rf). The observation of iron dissolution and oxygen consumption was carried out by applying the appropriate SECM tip potential in the MoO3 modified nanocomposite coated steel. The epoxy and epoxy-MoO3 nanocomposite-coated samples were used to study the mechanical, adhesion and anticorrosion properties. The analysis using SEM/EDX displayed that the enriched Mo was detected in the nanocomposite coated steel. The presence of the nano level corrosion product containing Mo was confirmed by FIB-TEM analysis. The high corrosion protection properties of the epoxy based nanocomposite coating was due to the complex nanoscale layer formed and chemical interactions of epoxy resin with surface-modified nanoparticle in nanocomposites.

Ultra-light polymer-based nano-composite for structural applications

Reduced cost and mass scale production of nano-composites in the future can provide economic feasibility for realizing their applications. In this work the effect of both synthetic filler graphene (GA) and organic filler henquen fiber (HF) infused in polymer matrix to study mainly the strength aspects for intended structural applications is carried out. This work also aims at determining the effect of nano and micro level reinforcement offered by graphene and HF as individual and combination in modifying the strength aspects for intended structural application. The addition of HF in the control beams was varied from 0.5 to 1% by weight of polymer matrix keeping graphene proportion constant. Dispersion of graphene was carried out by ultrasonic energy. Modified beams were subjected to tensile test to determine the efficacy of the reinforcement. These outcomes were then compared with the plain polymer beams. This study also aims at determining the best combination between these two fillers that leads to optimized mechanical performance. In order to enhance strength of the modified beams an effort was also made to treat natural fibers with alkaline and potassium permanganate treatment as individual and combination. Among the surfactant coatings made the fibers treated with both alkaline and permanganate treatment has shown enhanced results. An increase in the ultimate strength of the composite with a value of 27.13 N/mm2 for 0.5% natural fiber by weight of epoxy resin was noted. An increase in ultimate strength by 74% for graphene filler reinforcement when compared to plane epoxy was recorded. Similarly an increase in strength by 67% was observed when optimized proportions of HF and Graphene were used as reinforcements in holding matrix when compared to plain epoxy samples. Scanning Electron Microscopy was conducted to study the dispersion of these micro and nano fillers in the holding matrix at different proportions.

Effect of temperature cycling on performance of epoxy resin and evaluation of state

Epoxy resin samples were prepared according to the most common types of epoxy resins and curing agents in the market. The material was temperature-circulated at -40 to 150°C to investigate the effect of temperature cycling on the dielectric properties and bending properties of the material. The results show that with the increase of the number of temperature cycles, the relative dielectric constant, dielectric loss, flexural strength and flexural modulus of epoxy resin increase first, then decrease and then increase, and the electrical conductivity increases. Based on the samples of various performance values of epoxy resin in different times, an evaluation model based on BP neural network was established to evaluate the state of epoxy resin.

Strengthening of Reinforced Concrete Beams Using Bamboo Fiber/Epoxy Composite Plates in Flexure

Fiber reinforced polymer (FRP) is widely used in the construction industry for structural strengthening due to their outstanding mechanical properties. However, the production of synthetic fibers such as FRP is detrimental to the environment. Alternatively, natural fiber composite may be used as external strengthening material. This paper presents the potential of bamboo fiber composite plate (BFCP) to strengthen the reinforced concrete (RC) beams in flexure. The bamboo of species Dendrocalamus asper was used to produce the fiber and fiber-to-volume ratio was set at 2:5. The composite plate was fabricated by binding bamboo fibers with epoxy using a hand-lay-up method. The flexural and tensile strength of the BFCP was measured and all the beams were tested to failure under four-point bending test. It was found that BFCP exhibited a higher flexural and tensile strength compared to pure epoxy samples. Meanwhile, the RC beams strengthened using BFCP exhibited an increment of 10-12% in beam structural capacity compared to the un-strengthened beams. Bonding of BFCP in the flexure zone was able to divert the vertical cracks into diagonal at the edge of the composite plate. Findings from this work may serve as a useful guide to strengthen RC beams using a BFCP.

Electrical and Chemical Properties of Graphene over Composite Materials: A Technical Review

Graphene is a material that has superior mechanical, electrical, and thermal properties. It has drawn the attention of many scientific researchers for this purpose. In this paper, three different types of fillers, GNPs, MWCNTs and EG reinforced epoxy nanocomposites were mainly studied. Different shear mixing speeds and shear mixing times were considered during the study of the nanocomposites with 0.1 wt% loading of the fillers. The effects of various types of fillers and different shear mixing speeds and durations on mechanical and electrical properties of the final composites were examined. The GNPs-reinforced epoxy nanocomposite was the only one that showed a 13% improvement in elastic modulus as compared to pure epoxy when the shear mixing conditions were 3000 rpm for 2 hours. The research also studied the effects of different loadings of GNPs and the addition of acetone as a solvent on the final mechanical, electrical and thermal properties of the composites (with the fixed shear mixing speed and time). The tensile strength of the composites reduced drastically when the loading of GNPs increased while the elastic modulus shows some increase with the growth in GNP loading. The study found that GNPs reinforced composites did not show the percolation threshold even with 5 wt% (with the ratio to the weight of epoxy) loading of the GNPs. The GNPs-reinforced epoxy composites showed an 116% improvement in the thermal conductivity as compared to the pure epoxy samples when the GNPs loading was 5 wt%. The results from the studied literatures also showed that the samples prepared with the addition of acetone had higher thermal diffusivity than the samples prepared without acetone.

Cyclic Moisture Sorption and its Effects on the Thermomechanical Properties of Epoxy and Epoxy/MWCNT Nanocomposite.

The aim of this work was to reveal the moisture absorption–desorption–resorption characteristics of epoxy and epoxy-based nanocomposites filled with different multiwall carbon nanotubes (MWCNTs) by investigating the reversibility of the moisture effect on their thermomechanical properties. Two types of MWCNTs with average diameters of 9.5 and 140 nm were used. For the neat epoxy and nanocomposite samples, the moisture absorption and resorption tests were performed in atmospheres with 47%, 73%, and 91% relative humidity at room temperature. Dynamic mechanical analysis was employed to evaluate the hygrothermal ageing effect for unconditioned and environmentally “aged” samples. It was found that moisture sorption was not fully reversible, and the extent of the irreversibility on thermomechanical properties was different for the epoxy and the nanocomposite. The addition of both types of MWCNTs to the epoxy resin reduced sorption characteristics for all sorption tests, improved the hygrothermal and reduced the swelling rate after the moisture absorption–desorption.

Preparation and mechanical properties of green epoxy nanocomposites with cellulose nanocrystals

Epoxy resin is widely used to make composites, electronic and electric parts, adhesives, and coating materials because it has excellent thermal, electrical, and mechanical properties. Using natural materials in making epoxy composites and nanocomposites would make the final products greener. Therefore, in this study, epoxidized soybean oil (ESO) and cellulose nanocrystals (CNCs) were used to make green epoxy nanocomposites. ESO was prepared by epoxidation of soybean oil with peroxyacetic acid and it was confirmed by Fourier transform infrared spectroscopy. The ESO was mixed with diglycidyl ether of bisphenol A at different weight ratios (10%–50%) and the stoichiometric amount of ethylene diamine was used for curing. CNC content in the nanocomposites was changed from 0.125 to 1 phr. Mechanical properties of the epoxy samples and the nanocomposites were investigated by universal testing machine and izod impact tester. The epoxy sample showed best mechanical properties at ESO 30%. The nanocomposite with CNC 0.25 phr showed best mechanical properties. Fracture surfaces of the epoxy sample and the nanocomposites were investigated by scanning electronic microscope. POLYM. ENG. SCI., 60:439–445, 2020. © 2019 Society of Plastics Engineers

Processing and characterization analysis of pyrolyzed oil rubber (from waste tires)‐epoxy polymer blend composite for lightweight structures and coatings applications

In this experimental investigation, the authors have fabricated and characterized composites made from pyrolysis oil rubber and epoxy resin. As the dumping of waste scrap tires poses a serious environmental threat, the pyrolysis oil rubber was extracted from these waste tires only. The prepared blend having pyrolysis oil with various weight percentages (wt%) was examined on the basis of various physical, microstructural, mechanical, and thermal tests. The microstructural tests (scanning electron microscopy and X‐ray diffraction) analysis complemented with the mechanical tests (tensile, compression, flexural, hardness, and impact) results and confirmed that the 4.4 wt% of pyrolysis oil in epoxy resin sample exhibited the best results in toughening of the polymer network. Furthermore, the thermal analysis (differential thermal analysis and thermogravimetric analysis), electrical conductivity, density, water absorption, gas chromatography–mass spectroscopy, and Fourier‐transform infrared tests for the composites were also performed. Low density and high tensile strength than neat epoxy resin makes this composite a potential candidate for fabricating lightweight structures and in polymer coatings for automotive industries. POLYM. ENG. SCI., 59:2041–2051, 2019. © 2019 Society of Plastics Engineers

Study of The Phenomena of Surface Discharges and Flashover in Nanocomposite Epoxy Resin under the Influence of Homogeneous Electric Fields

A new class of insulating materials is the class of polymer nanocomposites. In the past twenty-five years, a lot of attention was paid to the various electrical, thermal and mechanical properties of polymer nanocomposite materials. In the present work, epoxy resin samples without and with nanoparticles (0 wt%, 1 wt%, 3 wt%, 5 wt%, and 10 wt%) are investigated regarding the surface discharges and the flashover voltages. Four different water droplet arrangements were used, with eight different water conductivities in order to see the effect of the nanoparticle.

Electrical Detection of Creeping Discharges over Insulator Surfaces in Atmospheric Gases under AC Voltage Application

Creeping discharges over insulator surfaces have been related to the presence of triple junctions in compressed gas insulated systems. The performance of dielectric materials frequently utilised in gaseous insulating high voltage applications, stressed under triple junction conditions, has been an interesting topic approached through many different physical perspectives. Presented research outcomes have contributed to the understanding of the mechanisms behind the related phenomena, macroscopically and microscopically. This paper deals with the electrical detection of creeping discharges over disc-shaped insulator samples of different dielectric materials (polytetrafluoroethylene (PTFE), epoxy resin and silicone rubber) using atmospheric gases (dry air, N2 and CO2) as insulation medium in a point-plane electrode arrangement and under AC voltage application. The entire approach implementation is described in detail, from the initial numerical field simulations of the electrode configuration to the sensing and recording devices specifications and applications. The obtained results demonstrate the dependence of the generated discharge activity on the geometrical and material properties of the dielectric and the solid/atmospheric gas interface. The current work will be further extended as part of a future extensive research programme.

Effect of interphase on dielectric relaxation mechanisms in epoxy-alumina nanocomposite

The interphase formed between polymer and a nanoparticle plays a critical role in the dielectric properties of the nanocomposite material. The effect of interphase on dielectric relaxation mechanisms is analyzed in this work. Unfilled epoxy and epoxyalumina nanocomposite samples with 0.l, 1 and 5 wt% filler loadings are prepared. SEM analysis is conducted to ensure dispersion of nanoparticles. Impedance and permittivity measurements are taken over the frequency range of 10 mHz-10 MHz. Equivalent circuit models are derived from impedance spectroscopy measurements for unfilled and nanofilled samples. A method based on genetic algorithm is used to optimize the equivalent circuit parameters. Initialization of parameters for the algorithm is selected based on the shape of Cole-Cole plot. The proposed equivalent circuit models based on relaxation time constants indicate the presence of polarization at the interphase region in nanocomposite. Variations in configuration and parameters of equivalent circuit for unfilled and filled epoxy are used to analyze the effect of interfacial polarization. Polarization at the interphase is differentiated from other relaxation mechanisms at 0.1 and 1 wt% based on equivalent circuit model. At 5 wt%, the optimized equivalent circuit configuration and corresponding relaxation time constants different from circuit models for other filler loadings is attributed to the presence of overlapping of interphases.

Effects of environmental exposures on carbon fiber epoxy composites protected by metallic thin films

Carbon fiber epoxy composites have a wide range of applications in aerospace, construction, and automotive industries due to their good mechanical properties and lightweight characteristics. Carbon fiber epoxy composite structures are typically intended for service in corrosive and hostile environmental conditions. Therefore, development of coatings which are able to protect carbon fiber epoxy composite laminates against prolonged and harsh environmental conditions such as ultraviolet radiation and moisture deems critical. This paper offers a novel method for environmental protection of fiber-reinforced polymer composites by applying thin metallic films on composites' surface as coating materials. In order to investigate the protective properties of metallic thin films, copper and aluminum coatings were deposited on the surface of carbon fiber epoxy specimens by using direct current magnetron-sputtering technique, and then mechanical properties and surface morphology of specimens were monitored during the course of accelerated environmental exposure. Both metallic coatings showed good adhesion to carbon fiber epoxy samples during environmental aging and provided protection for the specimens' surface against environmental degradation. The correlation between flexural properties and surface morphology of carbon fiber epoxy specimens is also presented.

Impact behavior of pine needle fiber/pistachio shell filler based epoxy composite

Natural filler/fiber based composites are material focusing on the use of natural reinforcement material for fabrication process. In present research two different composites are developed using (i) pine needle fiber and epoxy (ii) pistachio shell filler and epoxy. Impact strength of developed composites is studied which shows that with addition of pistachio shell filler and pine needle fibers in composites, there is increase in impact strength as compared to neat epoxy sample. In addition, hybrid composite with natural filler and pine needle fiber has shown the highest impact strength of 23.33 kJ/m2. Investigating samples further in different conditions (petrol, kerosene, water) for impact strength, research shows that there is substantial decrease in strength in comparison to the samples subjected to ambient conditions.

Metal-organic frameworks filled epoxy composites: exploring new chances for low-κ polymer dielectrics

ABSTRACTHerein, a simple strategy was proposed to explore new chances for low-κ epoxy composites by adding ZIF-8 as additive. Compared with that of pure epoxy sample, the dielectric constant of the epoxy/ZIF-8 composite (0.3 wt%) was decreased to 3.45 from 4.12, the dielectric loss was decreased, the AC electrical resistivity was increased, and the water absorption was decreased from 0.41% to 0.18%. Moreover, the epoxy/ZIF-8 composites possessed improved thermal stability under air atmosphere. Motivated by these results, the ZIF-8 was identified as a promising candidate for preparing low-κ epoxy composite, which maybe get further development in the future.