Electrical Properties Of Epoxy Nanocomposites Research Articles

Dispersion mechanism of nanoparticles and its role on mechanical, thermal and electrical properties of epoxy nanocomposites - A Review

The combined effect of nano-reinforcements on the mechanical performance of nanocomposites, which are a novel class of epoxy matrix hybrid nanocomposites containing multiwall carbon nanotubes (MWCNT), graphene, and nanodiamonds (NDs), is drawing substantial attention from many research communities. The discussion concentrates on the dispersion techniques adopted for the preparation of epoxy composites containing different types of nanoparticles (3-D fillers, nanofibers, nanotubes, and plate-like fillers). This review paper covers the electrical, thermal, and mechanical properties of carbon nanotubes (CNTs), graphene, and nanodiamond-reinforced epoxy nanocomposites and correlates them with the topographical features, morphology, weight fraction, dispersion state, and surface functionalization of CNTs, graphene, and nanodiamond. This review paper also summarises recent developments in the dispersion method of different carbon nanoparticles in epoxy matrix.

Mechanical, Thermal and Electrical Properties of Epoxy Nanocomposites with Amine-Functionalized Reduced Graphene Oxide via Plasma Treatment

A suitable functionalization of graphene and its derivatives can further enhance the material properties of nanocomposites. In contrast to chemical functionalization methods that have been extensively researched, functionalization by plasma treatment is relatively unexplored. In this work, we compare the mechanical, thermal and electrical characteristics of an epoxy matrix incorporating loadings from 0.00 to 1.50 wt% of non-functionalized (rGO) and amine-functionalized reduced graphene oxide (frGO) for which the functionalization is realized by plasma processing. No significant difference between the rGO- and frGO-including nanocomposites was observed with respect to the stiffness, strength, specific heat capacity, coefficient of thermal expansion and electrical conductivity. Yet, the composites with 1.50 wt% frGO (rGO) exhibited a thermal conductivity that was 27% (20%) higher than the neat polymer due to the enhanced interface, which enabled a better transfer of heat. In addition, a considerable increase in the specific heat capacity and thermal conductivity was established with rising temperatures. This information will facilitate the choice of materials depending on the loading and functionalization of graphene materials for composite applications with an epoxy matrix.

Investigating optimal region for thermal and electrical properties of epoxy nanocomposites under high frequencies and temperatures

This research investigates the optimal region to achieve balanced thermal and electrical insulation properties of epoxy (EP) under high frequency (HF) and high temperature (HT) via integration of surface-modified hexagonal boron nitride (h-BN) nanoparticles. The effects of nanoparticle content and high temperature on various electrical (DC, AC, and high frequency) and thermal properties of EP are investigated. It is found that the nano h-BN addition enhances thermal performance and weakens electrical insulation properties. On the other side, under HF and HT stress, the presence of h-BN nanoparticles significantly improves the electrical performance of BN/EP nanocomposites. The EP has superior insulation properties at low temperature and low frequency, whereas the BN/EP nanocomposites exhibit better insulation performance than EP under HF and HT. The factors such as homogeneous nanoparticle dispersion in EP, enhanced thermal conductivity, nanoparticle surface modification, weight percent of nanoparticles, the mismatch between the relative permittivity of EP and nano h-BN, and the presence of voids in nanocomposites play the crucial role. The optimal nanoparticle content and homogenous dispersion can produce suitable EP composites for the high frequency and high temperature environment, particularly solid-state transformer applications.

Effect of non-covalent functionalization of graphene-based nanoparticles on the local electrical properties of epoxy nanocomposites

In this study, we put forward a non-covalent π-π interaction between graphene nanoparticles (G) and a pyrene-based molecule (py) to give the functionalized graphene (G-py). The proposed modification has proven to be a winning solution aimed at safeguarding the graphene’s striking electronic properties, while favoring a more effective nanofiller dispersion due to a decrease in viscosity with consequent improvement of the rheological properties of the formulated nanocomposites. Tunneling Atomic Force Microscopy (TUNA) analysis was carried out using G-py weight percentages both below and above the Electrical Percolation Threshold (EPT) to investigate the electrical behavior of the conductive nanodomains of the epoxy/graphene systems. The electrical results are in perfect agreement with the rheological ones. The non-covalent modification greatly enhances the thermal stability of the graphene-based nanoparticles, also causing an increase in the oxidative thermostability of the formulated nanocomposites.

The role of graphene interactions and geometry on thermal and electrical properties of epoxy nanocomposites: A theoretical to experimental approach

The influence of dispersion procedure and nanofiller geometry on thermal and electrical properties of graphene nanoplatelet (GNP) based composites has been investigated. A theoretical model, based on the contacts between adjacent nanoparticles, has been proposed aiming to connect thermal and electrical properties. It has been observed that GNP overlapping (type I) induces a decrease on thermal conductivity. Its effect on electrical conductivity is more complex and depends on the areas of overlap and in-plane contacts (type II). A higher type I area in comparison to type II implies an increase of electrical conductivity with overlapping whereas the opposite effect is found when type II area is higher than type I. The predicted results of the theoretical model fitted experimental measurements at different GNP contents and three roll milling processing conditions, giving a better overview of the influence of GNP geometry and interactions on electrical and thermal properties of nanocomposites.

Synergistic Effects of Boron Nitride (BN) Nanosheets and Silver (Ag) Nanoparticles on Thermal Conductivity and Electrical Properties of Epoxy Nanocomposites.

Polymer composites, with both high thermal conductivity and high electrical insulation strength, are desirable for power equipment and electronic devices, to sustain increasingly high power density and heat flux. However, conventional methods to synthesize polymer composites with high thermal conductivity often degrade their insulation strength, or cause a significant increase in dielectric properties. In this work, we demonstrate epoxy nanocomposites embedded with silver nanoparticles (AgNPs), and modified boron nitride nanosheets (BNNSs), which have high thermal conductivity, high insulation strength, low permittivity, and low dielectric loss. Compared with neat epoxy, the composite with 25 vol% of binary nanofillers has a significant enhancement (~10x) in thermal conductivity, which is twice of that filled with BNNSs only (~5x), owing to the continuous heat transfer path among BNNSs enabled by AgNPs. An increase in the breakdown voltage is observed, which is attributed to BNNSs-restricted formation of AgNPs conducting channels that result in a lengthening of the breakdown path. Moreover, the effects of nanofillers on dielectric properties, and thermal simulated current of nanocomposites, are discussed.

The Effect of Hybridized Carbon Nanotubes, Silica Nanoparticles, and Core-Shell Rubber on Tensile, Fracture Mechanics and Electrical Properties of Epoxy Nanocomposites.

The paper investigates the effect of adding a combination of rigid nanoparticles and core-shell rubber nanoparticles on the tensile, fracture mechanics, electrical and thermo-mechanical properties of epoxy resins. SiO2 nanoparticles, multi-walled carbon nanotubes (MWCNT’s), as rigid nanofillers, and core-shell rubber (CSR) nanoparticles, as soft nanofillers were used with bisphenol-A-based epoxy resin. Further, the rigid fillers were added systematically with core-shell rubber nanoparticles to investigate the commingled effect of rigid nanofillers and soft CSR nanoparticles. The resulting matrix will be broadly evaluated by standard methods to quantify tensile, fracture mechanics, electrical, and thermal properties. The results show that the electrical conductivity threshold is obtained at 0.075 wt. % for MWCNT-modified systems. For hybrid systems, the maximum increase of fracture toughness (218%) and fracture energy (900%) was obtained for a system containing 5 wt. % of CSR and 10 wt. % of SiO2. The analysis of the fracture surfaces revealed the information about existing toughening micro-mechanisms in the nanocomposites.

Thermal and electrical properties of the epoxy nanocomposites reinforced with purified carbon nanotubes

The effect of carbon nanotube (CNT) purification treatment on the thermal and electrical properties of epoxy nanocomposites was investigated. The results indicated that purification treatment can significantly affect nanocomposite performance including thermal and electrical properties. Highly-purified single-walled carbon nanotubes (SWCNTs) have the potential to significantly improve the thermal conductivity of polymer nanocomposites, but are unfavorable for electrical properties due to their inability to form an effective percolating network. The thermal conductivity can be improved up to four times higher than the polymer matrix, demonstrating the significance of CNT purification treatment in improving nanocomposite performance. The electrical conductivity of polymer nanocomposites is more sensitive to purification treatment than their thermal conductivity.

High-efficiency enhancement on thermal and electrical properties of epoxy nanocomposites with core-shell carbon foam template-coated graphene

Recently, three-dimensional graphene foam has received considerable attention and displayed excellent properties as reinforcement for polymer composites. However, the brittleness and poor controllability limited its application in resin to form conducting pathways for phonons and electrons. This study developed a facile method with compressible and constitutionally stable commercial melamine foam (MF) as template to prepare a core-shell composite with carbon skeleton structure. The core carbon structure was fabricated by carbonization of MF, while the shell carbon structure was the in-situ self-assembled coating of graphene. Vacuum-impregnated method was employed to fabricate epoxy resin composites. The thermal and electrical conductivities of epoxy composites were significantly increased to 0.92 W/(m·K) and 0.70 S/cm, which was 318% and 13 orders of magnitude higher than that of pure epoxy. Herein, we provide a highly efficient, green, high-quality method for building a double-layer heat conduction path, which facilitates the utilization of graphene. The proposed method proves to be efficient in enhancing the multifunctionality of epoxy resin composites. Furthermore, we explored the thermal and electrical conductive mechanisms of the three-dimensional core-shell structure in resin matrix.

Electrical properties of epoxy nanocomposites containing Fe3O4 nanoparticles and Fe3O4 nanoparticles deposited on the surface of electrochemically exfoliated and oxidized graphite

Electrical conductivity, electromagnetic interference shielding and microwave absorption properties of epoxy composites containing magnetite nanoparticles and modified electrochemically exfoliated graphite (mEEG) were described in this work. Different nanoparticles were prepared by co-precipitation method and electrochemical exfoliation. Structure of synthesized Fe3O4 NPs and graphite based nanostructures was described in detail. The X-ray diffractometry, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy as well as scanning and transmission electron microscopy were used in order to characterize samples. Fe3O4 nanoparticles with average crystallite size equal to 8.45 nm and 8.30 nm were obtained in highly agglomerated structure and on the surface of mEEG. Reconstruction of graphite structure during precipitation of Fe3O4 on the surface of oxidized, exfoliated graphite was observed. In order to describe dispersion of AC electrical conductivity, correlated barrier hopping model was used. It was noticed, that addition of nanoparticles changes the values of hopping energy and activation energy as well as electromagnetic interference shielding and microwave absorption properties. Epoxy composite containing Fe3O4 NPs had the highest value of activation energy of electrical conductivity. It was shown, that the addition of magnetite nanoparticles has also improved electromagnetic interference shielding and microwave absorption properties of epoxy resin.

Effect of Carbon Nanotube Aspect Ratio on the Thermal and Electrical Properties of Epoxy Nanocomposites

The novel properties of carbon nanotubes have generated much interest in polymer nanocomposites. The thermal and electrical properties of multi-walled carbon nanotube-epoxy composites were investigated both experimentally and theoretically. Experiments were performed to evaluate the effect of the aspect ratio of carbon nanotubes. Comparisons were made between the results obtained for the nanocomposite materials containing carbon nanotubes with a high (800) and a low (80) aspect ratios. Design recommendations were made, and potential applications were also discussed. It was shown that the aspect ratio plays an important in determining the physical properties of the epoxy nanocomposite. The electrical conductivity of the nanocomposite is highly dependent on the aspect ratio of carbon nanotubes. In contrast, the aspect ratio plays a considerable role in the thermal conductivity of the nanocomposite. Carbon nanotubes have clearly demonstrated their capability as thermally and electrically conductive fillers in epoxy nanocomposites. In contrast to the orders of magnitude enhancement in electrical conductivity with a very low loading of carbon nanotubes, the thermal conductivity of the nanocomposite has shown only moderate improvement. The improvement in physical properties of the nanocomposite can be interpreted in terms of carbon nanotube networks.

Role of chemical funcionalization of carbon nanoparticles in epoxy matrices

The effects of the silanization of multi-walled carbon nanotubes and graphene nanoplatelets with 3-APTES on thermal, mechanical and electrical properties of epoxy nanocomposites were investigated. Nanocomposites containing pristine, oxidized and silanized nanoparticles of multi-walled carbon nanotubes or graphene nanoplatelets at two different concentrations (0.15 and 0.50 vol.%) were prepared by in situ polymerization without using solvents. The functionalized nanoparticles were characterized by Fourier-transform infrared, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscope techniques. The oxidation and the silanization on the surface of both nanoparticles were confirmed by Fourier-transform infrared, X-ray photoelectron spectroscopy, Raman and transmission electron microscope analysis. The thermal properties of all studied materials were analyzed by differential scanning calorimetry and the mechanical properties by nanoindentation. The addition of both nanoparticles (pristine and functionalized) into the matrix did not show significant variations on thermal properties, but decreased values for glass transition temperature (Tg) compared to the neat resin. Higher values for modulus of elasticity and hardness of epoxy/nanocomposites were obtained when silanized multi-walled carbon nanotubes or oxidized graphene nanoplatelets were added into the matrix. Adding 0.15 vol.% of silanized multi-walled carbon nanotubes the modulus of elasticity increased in approximately 60%, whereas 0.50 vol.% this increase was greater than 90% compared to the neat resin. While adding 0.15 vol.% of oxidized graphene nanoplatelets, the modulus of elasticity increased approximately 83%, whereas 0.50 vol.% this increase was greater than 88% compared to the neat resin. The formation of percolating networks has been achieved only by pristine multi-walled carbon nanotubes addition at a concentration of 0.50 vol.% and by silanized graphene nanoplatelets at a concentration of 0.15 vol.%. However, for both carbon-based nanoparticles conductivities on the order of 10−7 S/m for frequencies near 100 Hz were observed.

Significantly enhanced mechanical and electrical properties of epoxy nanocomposites reinforced with low loading of polyaniline nanoparticles

Enhanced mechanical and electrical properties were observed in the polyaniline–epoxy nanocomposites prepared by three different techniques.

Role of Surface Functionalisation of Multiwall Carbon Nanotubes on Nanomechanical and Electrical Properties of Epoxy Nanocomposites

The key point of this work is to study the evolution of nanomechanical and electrical properties of epoxy nanocomposites, as varying the multiwall carbon nanotube content and the surface functionalisation of nanotubes. The concentration dependence of physical and mechanical properties reveals some specific features and this depends strongly on the amine-functionalisation of nanotube surfaces. The composite structure at the nanoscale, visualised by SEM, shows a homogeneous dispersion and a presence of bond polymer layer around the functanalised nanotube surfaces, these resulting in a significant nano-reinforcement effects. In contrast, the non-functionalised nanotube composites show much higher dc-conductivity, than the amine-functionalized one, as conductivity depends strongly on the interactions of nanotubes. Both mechanical and electrical percolation thresholds appear at very low nanotube contents around 0.03–0.05 wt%, depending differently on the surface functionalisation of nanotubes. Both percolation thresholds are used for establishing a structure-property relationship, this providing a prediction about the effectiveness of the nanotube content and surface functionalisation for the maximum improvement of electrical and nanomechanical properties of the MWCNT/epoxy nanocomposite.

Hybrid nanocomposites containing carbon nanotubes and graphite nanoplatelets

The effects of hybrid carbon nanotubes (CNT) and graphite nanoplatelets (GNPs) on the mechanical and electrical properties of epoxy nanocomposites were studied. When the total reinforcement contents is fixed at 2 wt.%, the nanocomposite containing 1% GNP and 1% CNT achieves the highest electrical conductivity of 4.7 × 10 −3 S/cm, which is more than two orders of magnitude higher than that of nanocomposites with 2 wt.% GNP alone. Although the flexural properties are only marginally changed by hybridization, the quasi-static fracture toughness can be enhanced significantly by increasing the CNT content.

Understanding the thermal, mechanical and electrical properties of epoxy nanocomposites

In the present work, the electrical, mechanical and thermal properties of epoxy nanocomposite materials were studied. The electrical insulation characteristics were analyzed through short time breakdown voltage test, accelerated electrical ageing test, and by tracking test. The breakdown voltage increases with increase in nano-clay content up to 5 wt%, under AC and DC voltages. The volume resistivity, permittivity and tan( δ) of the epoxy nanocomposites were measured. The Weibull studies indicate that addition of nanoclay upto 5 wt% enhances the characteristic life of epoxy nanocomposite insulation material. The tracking test results indicate that the tracking time is high with epoxy nanocomposites as compared to pure epoxy. Ageing studies were carried out to understand the surface characteristic variation through contact angle measurement. The hydrophobicity of the insulating material was analysed through contact angle measurement. The diffusion coefficients of the material with different percentage of clay in epoxy nanocomposites were calculated. The exfoliation characteristics in epoxy nanocomposites were analyzed through wide angle X-ray diffraction (WAXD) studies. The thermal behaviour of the epoxy nanocomposites was analyzed by carrying out thermo gravimetric-differential thermal analysis (TG-DTA) studies. Heat deflection temperature of the material was measured to understand the stability of the material for intermittent temperature variation. The dynamic mechanical analysis (DMA) results indicated that storage modulus of the material increases with small amount of clay in epoxy resin. The activation energy of the material was calculated from the DMA results.