Graphene/nanorubber reinforced electrically conductive epoxy composites with enhanced toughness

Graphene platelets (electrically conductive 2D filler) and rubber nanoparticles (0D soft filler) can work together to develop electrically conductive and toughened epoxy composite adhesives. In this study, complementing effect between graphene platelets (GnPs) and rubber nanoparticles (RnPs) within an epoxy matrix is reported. In the 3-phase composite adhesive, the 2D graphene platelets form global conductive network and rubber nanoparticles provide a viscoelastic phase inside the epoxy, both complementing each other to develop electrically conductive and toughened epoxy composite adhesives. Fracture toughness (K_1c) and critical strain energy release rate (G_1c) of the epoxy were augmented by 422% and 872%, respectively by adding 1 wt% RnPs and it recorded electrical percolation threshold at 0.78 vol% GnP. Also, the Young's modulus and strength of epoxy/1 wt% RnP composite were promoted from 1.57 to 2.32 GPa when 1 wt% GnP is added. Scanning electron microscopy analysis was conducted to investigate the toughening mechanism of epoxy/RnP/GnP and epoxy/GnP composites. Lap shear strength tests on epoxy composite adhesives confirm the reinforcement effect of GnPs and toughness effect of RnPs.     

Synergistic effect of graphene and carbon nanotube on lap shear strength and electrical conductivity of epoxy adhesives

In this study, synergy between graphene platelets (GnPs) and carbon nanotubes (CNTs) in improving lap shear strength and electrical conductivity of epoxy composite adhesives is demonstrated. Adding two-dimensional GnPs with one-dimensional CNTs into epoxy matrix helped to form global three-dimensional network of both GnPs and CNTs, which provide large contact surface area between the fillers and the matrix. This has been evidenced by comparing the mechanical properties and electrical conductivity of epoxy/GnP, epoxy/CNT, and epoxy/GnP-CNT composites. Scanning electron microscopic images of lap shear fracture surfaces of the composite adhesives showed that GnP-CNT hybrid nanofillers demonstrated better interaction to the epoxy matrix than individual GnP and CNT. The lap shear strength of epoxy/GnP-CNT composite adhesive was 89% higher than that of the neat epoxy adhesive, compared with only 44 and 30% increase in the case of epoxy/GnP and epoxy/CNT composite adhesives, respectively. Electrical percolation threshold of epoxy/GnP-CNT composite adhesive is recorded at 0.41 vol %, which is lower than epoxy/GnP composite adhesive (0.58 vol %) and epoxy/CNT composite adhesive (0.53 vol %), respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48056.     

Flexible strain sensors based on epoxy/graphene composite film with long molecular weight curing agents

Flexible strain sensors based on epoxy/graphene composite film with long molecular weight curing agents have critical roles in the development of advanced polymer composite films that combine mechanical robustness with functional properties such as electrical conductivity for many applications. In this experiment, flexible epoxy/GnP composite film is obtained by using flexible curing agent J2000. A percolation threshold of electrical conductivity was observed at merely 0.97 vol% GnPs, and the composite electrical conductivity increased to 10⁻⁶ S/cm at 5.0 vol %. The composite films were mechanically strong enough to be used as a flexible strain sensor. Our sensor can clearly detect the stretching of the forearm skin caused by a fist pulse and back of hand movement and achieve an enhancement of the resistance signal of up to 50%. When the GnPs content reaches 5%, Young's modulus and tensile strength increase to 21 MPa and 1.3 MPa, respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47906.     

Accurate self-damage detection by electrically conductive epoxy/graphene nanocomposite film

Detecting and locating accurately structure damages at an early stage is essential to minimization of catastrophic disasters, prevention of fatalities and provision of cost-effective maintenance. We herein report a facile approach to detect structure damages and to accurately identify their locations by using an electrically conductive epoxy/graphene nanocomposite film. A percolation threshold of electrical conductivity was observed at 0.58 vol% of graphene platelets (GnPs, ~3 nm in thickness and ~15 μm in length); electrical conductivity of 3.3 S/cm was obtained at 9.00 vol% of GnPs. The epoxy/GnP composite film containing 9.00 vol% of GnPs was employed as an array of electrically conductive paths in horizontal and vertical directions to detect and locate structure's damages. Thermal stability and temperature coefficient of the composite film were studied. Relative resistance change due to temperature effect was fitted into an exponential function, which showed strong correlation with the temperature change. This implies that an algorithm can be developed to compensate drift errors in resistance measurement due to temperature variation. With the help of Internet of Things, our self-sensing epoxy/graphene nanocomposite films have great potential for smart aerospace structural health monitoring.     

Size and synergy effects of nanofiller hybrids including graphene nanoplatelets and carbon nanotubes in mechanical properties of epoxy composites

We study mechanical reinforcement in a widely used epoxy matrix with the addition of graphene nanoplatelets (GnPs) and various mixture ratios of carbon nanotubes (CNTs) with GnPs. Two different dimensions of GnPs were used with flake sizes of 5 μm and 25 μm to investigate the influence of nanofiller size on composite properties. In GnP reinforced composites, bigger flakes showed greater reinforcement at all GnP concentrations as they actively control the failure mechanisms in the composite. In the mixture samples, highest CNT content (9:1) showed marked improvement in fracture toughness of 76%. The CNT:GnP ratio is an interesting factor significantly influencing the properties of the epoxy based nanocomposites. The combination of high aspect ratio of CNTs and larger surface area of GnPs contribute to the synergistic effect of the hybrid samples. Thermal conductivity consistently increases with incorporation of GnPs in the matrix. Transmission electron microscopy (TEM) images confirm the uniform nanofiller dispersion achieved in the composites. For the hybrid samples CNTs are seen to align themselves on the GnP flakes creating an inter-connected strong nanofiller network in the matrix. The homogeneous nanofiller dispersions have been achieved by high shear calendaring which is a method capable of being industrially scaled up.     

Toughness and roughness in hybrid nanocomposites of an epoxy matrix

The present paper investigates the relationship between roughness and toughening mechanisms in hybrid epoxy nanocomposites with carbon nanotubes (CNT) and graphene nanoplatelets (GNPs). The role of adding a block copolymer (BC) to the studied systems was also investigated. The nanocomposites were prepared by means of high‐energy sonication and in situ polymerization. All nanocomposites presented higher numerical values for K_Ic than untoughened systems. The system containing 0.5 wt% of CNTs presented an increase of 35% in K_Ic compared to neat epoxy, and the hybrid nanocomposite, at the proportion of 1:1 (CNT:GNP), with 0.5 wt% total of nanoparticles and also containing 0.5 wt% of BC, had an increase of 34% compared to the neat epoxy. Systems with higher amounts of graphene showed the highest roughness values, having crack deflection/exfoliation between the GNP layers as the main toughening mechanism. On the other hand, systems with more CNTs presented a lower fracture surface roughness, and the main toughening mechanism was bridging/break‐up of the nanotubes. Hybrid systems have more types of mechanisms than simple ones. With only one type of nanoparticle, however, some of those mechanisms are not effective in increasing the toughness, only increasing the fracture surface roughness. POLYM. ENG. SCI., 59:1258–1269 2019. © 2019 Society of Plastics Engineers     

Nanotailoring of polyurethane adhesive by polyhedral oligomeric silsesquioxane (POSS)

The development and commercialization of nanoparticles such as nanoclays (NCs), carbon nanotubes (CNTs) and polyhedral oligomeric silsesquioxanes (POSS) offers new possibilities to tailor adhesives at the nanoscale. Four types of POSS, with reactive mono-functional groups of isocyanatopropyl, glycidoxypropyl, aminoethyl and non-reactive octaphenyl, were incorporated in concentrations of 1, 3 and 5 wt% into a polyurethane (PU)-based adhesive. Thermo-mechanical bulk properties were studied using dynamic mechanical analysis (DMA). Adhesive properties were characterized in shear and peel modes. Atomic force microscopy (AFM) was used to study the nanoscale morphology. DMA measurements indicated that the neat PU possessed a glass transition temperature (T _g) of ≈ 30°C. The T _g of PU/POSS-glycidoxypropyl nanocomposite adhesive increased gradually with POSS concentration to 50°C for 5 wt%. PU/POSS-octaphenyl nanocomposite adhesive exhibited an increased T _g by 10°C for 5 wt%. The incorporation of POSS-isocyanatopropyl in the PU had no effect on the T _g. With respect to shear properties of POSS-octaphenyl-, POSS-isocyanatopropyl- and POSS-glycidoxypropyl-based PU nanocomposite adhesives, shear strength improved by 230, 178 and 137%, respectively, compared to neat PU. POSS-aminoethyl exhibited lower shear and peel strengths, while POSS-isocyanatopropyl provided the best balance of both higher shear and peel strengths compared to neat PU. It was concluded that the grafted functional group on the POSS and its reactivity with the PU network components were the decisive factors with respect to the thermo-mechanical, morphological and adhesive properties of the resulting nanocomposite adhesives. Consequently, the POSS/polyurethane based nanocomposite adhesives could be tailored for a large range of applications.     

Promotion of the mechanical properties and thermal conductivity of epoxy by low Si3N4 whisker content and its mechanisms

Si₃N₄ whisker (Si₃N_4w) is selected as epoxy filler. The influence of filler content on the bulk density, porosity, bending strength, Young's modulus, critical stress intensity factor, work of failure, morphologies of fracture surface, and thermal conductivity of Si₃N_4w/epoxy is investigated. The bending strength is 82.63 MPa at a Si₃N_4w content of 5 vol% and increases to 25.29% more than that of neat epoxy. Compared with that of neat epoxy, the work of failure and thermal conductivity increase by 455% and 34.78% to 18 248.92 J·m⁻² and 0.31 W·m⁻¹·K⁻¹, respectively, at a Si₃N_4w content of 7 vol%. However, Si₃N_4w/epoxy becomes sensitive to precrack due to a weak C N bond and residual tensile stress at the interface, thereby resulting in the decline of critical stress intensity factor. The coexistence of various energy dissipation mechanisms, namely, steps, craters or depressions, stress whitening, plastic flow, pull out of Si₃N_4w, and rough fracture surface, is observed in Si₃N_4w/epoxy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48721.     

UV‐cured epoxy/graphene nanocomposite films: preparation,structure and electric heating performance

UV‐cured epoxy/graphene nanocomposite films with ca 100 µm thickness were manufactured by a facile cationic photopolymerization of 3,4‐epoxycyclohexylmethyl‐3′,4′‐epoxycyclohexane carboxylate mixtures including graphene sheets of 0.3 ? 10.0 wt%, which was initiated by triarylsulfonium hexafluoroantimonate salts. The microstructure and thermal and electrical properties of the UV‐cured epoxy/graphene nanocomposite films were investigated as a function of the graphene content. X‐ray diffraction patterns and TEM images confirm that graphene sheets are well dispersed in the UV‐cured epoxy resin matrix even with a high graphene content of 10.0 wt%. The electrical resistance of the nanocomposite films decreased dramatically from ca 10¹² Ω to ca 10² Ω with increasing graphene content, especially at a percolation threshold of 2.0 ? 3.0 wt%. Accordingly, the UV‐cured nanocomposite films including 5.0 ? 10.0 wt% graphene showed excellent electric heating performance in terms of temperature response as well as electric power efficiency at a given applied voltage. For a nanocomposite film with 10.0 wt% graphene, the maximum temperature of ca 138 °C was attained at an applied voltage of 15 V and a high electric power efficiency of ca 3.0 ± 0.3 mW °C^?1 was achieved. © 2014 Society of Chemical Industry     

Electrically and thermally conductive elastomer/graphene nanocomposites by solution mixing

The greatest challenge in developing polymer/graphene nanocomposites is to prevent graphene layers stacking; in this respect, we found effective solution-mixing polymers with cost-effective graphene of hydrophobic surface. Since graphene oxide is hydrophilic and in need of reduction, highly conducing graphene platelets (GnPs) of ∼3 nm in thickness were selected to solution-mix with a commonly used elastomer – styrene–butadiene rubber (SBR). A percolation threshold of electrical conductivity was observed at 5.3 vol% of GnPs, and the SBR thermal conductivity enhanced three times at 24 vol%. Tensile strength, Young's modulus and tear strength were improved by 413%, 782% and 709%, respectively, at 16.7 vol%. Payne effect, an important design criteria for elastomers used in dynamic loading environment, was also investigated. The comparison of solution mixing with melt compounding, where the same starting materials were used, demonstrated that solution mixing is more effective in promoting the reinforcing effect of GnPs, since it provides more interlayer spacing for elastomer molecules intercalating and retains the high aspect ratio of GnPs leading to filler–filler network at a low volume fraction. We also compared the reinforcing effect of GnPs with those of carbon black and carbon nanotubes.     

Microstructure,mechanical properties and toughening mechanisms of graphene reinforced Al2O3-WC-TiC composite ceramic tool material

The low fracture toughness of Al₂O₃-based ceramics limited their practical application in cutting tools. In this work, graphene was chosen to reinforce Al₂O₃-WC-TiC composite ceramic tool materials by hot pressing. Microstructure, mechanical properties and toughening mechanisms of the composite ceramic tool materials were investigated. The results indicated that the more refined and denser composite microstructures were obtained with the introduction of graphene. The optimal flexural strength, Vickers hardness, indentation fracture toughness were 646.31?±?20.78?MPa, 24.64?±?0.42?GPa, 9.42?±?0.40?MPa?m^1/2, respectively, at 0.5?vol% of graphene content, which were significantly improved compared to ceramic tool material without graphene. The main toughening mechanisms originated from weak interfaces induced by graphene, and rugged fractured surface, grain refinement, graphene pull-out, crack deflection, crack bridging, micro-crack and surface peeling were responsible for the increase of fracture toughness values.     

Microwave exfoliated reduced graphene oxide epoxy nanocomposites for high performance applications

Graphene has captured the attention of scientific community due to recently emerging high performance applications. Hence, studying its reinforcing effects on epoxy resin is a significant step. In this study, microwave exfoliated reduced graphene oxide (MERGO) was prepared from natural graphite for subsequent fabrication of epoxy nanocomposites using triethylenetetramine (TETA) as a curing agent via in-situ polymerization. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), C¹³ NMR spectroscopy, X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–vis) spectroscopy were employed to confirm the simultaneous reduction and exfoliation of graphene oxide. The reinforcing effect of MERGO on epoxy resin was explored by investigating its static mechanical properties and dynamic mechanical analysis (DMA) at MERGO loadings of 0 to 0.5 phr. The micro-structure of epoxy/MERGO nanocomposites was investigated using scanning electron microscope (SEM), transmission electron microscope (TEM) and XRD techniques. The present work reports an enhancement of 32%, 103% and 85% in tensile, impact and flexural strength respectively of epoxy by the addition of even 0.25 phr MERGO. At this loading elastic and flexural moduli also increased by 10% and 65%, respectively. Single-edge-notch three-point-Bending (SEN-TPB) fracture toughness (K_IC) measurements were carried out where a 63% increase was observed by the introduction of 0.25 phr MERGO. The interfacial interactions brought about by graphene also benefited the dynamic mechanical properties to a large extent in the form of a significant enhancement in storage modulus and slightly improved glass transition temperature. Considerable improvements were also detected in dielectric properties. The epoxy nanocomposite also attained an ac conductivity of 10⁻⁵ S/m and a remarkable increase in dielectric constant. The simple and cost effective way of graphene synthesis for the fabrication of epoxy/MERGO nanocomposites may be extended to the preparation of other MERGO based polymer nanocomposites. This remarkable class of materials has thrown open enormous opportunities for developing conductive adhesives and in microelectronics.     

From carbon nanotubes and silicate layers to graphene platelets for polymer nanocomposites

In spite of extensive studies conducted on carbon nanotubes and silicate layers for their polymer-based nanocomposites, the rise of graphene now provides a more promising candidate due to its exceptionally high mechanical performance and electrical and thermal conductivities. The present study developed a facile approach to fabricate epoxy-graphene nanocomposites by thermally expanding a commercial product followed by ultrasonication and solution-compounding with epoxy, and investigated their morphologies, mechanical properties, electrical conductivity and thermal mechanical behaviour. Graphene platelets (GnPs) of 3.57 ± 0.50 nm in thickness were created after the expanded product was dispersed in tetrahydrofuran using 60 min ultrasonication. Since epoxy resins cured by various hardeners are widely used in industries, we chose two common hardeners: polyoxypropylene (J230) and 4,4'-diaminodiphenylsulfone (DDS). DDS-cured nanocomposites showed a better dispersion and exfoliation of GnPs, a higher improvement (573%) in fracture energy release rate and a lower percolation threshold (0.612 vol%) for electrical conductivity, because DDS contains benzene groups which create π-π interactions with GnPs promoting a higher degree of dispersion and exfoliation of GnPs during curing. This research pointed out a potential trend where GnPs would replace carbon nanotubes and silicate layers for many applications of polymer nanocomposites.     

Thermal conductivity and lap shear strength of GNP/epoxy nanocomposites adhesives

The addition of graphene nanoplatelets (GNPs) into the epoxy adhesives has been studied in order to increase their thermal conductivity. Thermally conductive adhesives are often used as thermal interface materials (TIMs). The incorporation of 8 and 10 wt% GNPs reinforcement caused a thermal conductivity enhancement of ~206 and ~306%, respectively. The wettability seems to decrease with low GNPs content (2–3 wt%) in comparison with the neat epoxy adhesive but the contact angle remains constant for higher GNPs contents. Lap shear strength remains constant for neat adhesives and resins doped with GNPs. The lack of enhancement of adhesive properties of doped resins is due to a weak interface reinforcement-matrix. In fact, the joint failure is in the adhesive except for high GNPs content (10 wt%) where a cohesive failure mode is observed.     

Effect of multi-walled carbon nanotubes and silicon carbide nanoparticles on the deleterious influence of water absorption in adhesively bonded joints

In this study, the deleterious influence of hot deionized water on adhesively bonded joints was reduced with silicon carbide (SiC) nanoparticles and multi-walled carbon nanotubes (MWCNTs). A gravimetric method was used to study the kinetics of water ingress into the neat and nanocomposite epoxy adhesives. Then, joints were manufactured using the same neat and nanocomposite adhesives and aged for different periods according to the results obtained from the bulk sample tests and finite element modeling. The results showed that the reinforcing effect of nanofillers on the strength was about three times higher for the wet epoxy adhesive compared to the dry one. Moreover, it was found out that introducing 4.4 wt% of SiCs or 0.52 wt% of MWCNTs to the adhesive can compensate the degrading influence of aging under near-saturated condition. Furthermore, the scanning electron microscope (SEM) fractography was used to assess the fracture surfaces of the neat and reinforced samples.     

PDMS Nanodomains in DGEBA Epoxy Induce High Flexibility and Toughness

A nanostructured, highly flexible, and optically transparent epoxy nanocomposite has been formulated reacting diglycidyl ether of bisphenol-A with amine-functionalized silyl-diglycidyl ether-terminated poly(dimethylsiloxane). The concentration of poly(dimethylsiloxane) varied up to 10?wt% and curing was performed at 90°C. Transmission electron microscopy revealed poly(dimethylsiloxane) droplets up to 180?nm in diameter well dispersed in the epoxy. Dynamic mechanical analysis exhibited a decrease in elastic modulus E′ and glass transition temperature T_g, and an increase in the α relaxation strength suggesting increased local molecular motions. Strikingly, poly(dimethylsiloxane) induced a threefold increase in strain at fracture and toughness. Furthermore, hydrophobic behavior was induced by poly(dimethylsiloxane) as the water contact angle increased from 72° (neat epoxy) up to 110° at 5?wt% poly(dimethylsiloxane) content. Fractured surfaces exhibited plastic deformation, contrary to brittleness in the neat epoxy. These nanocomposites are attractive for coatings/encapsulates with improved flexibility, toughness, optical transparency, and water resistance.     

Plastic deformation-induced improved mechanical and thermal properties in hot-forged SiC-TiC composite

A novel SiC-20 vol% TiC composite prepared via a two-step sintering technique using 6.5 vol% Y₂O₃-Sc₂O₃-MgO exhibited high deformation (60 %) on hot forging attributed to the high-temperature plasticity of TiC (ductile to brittle transition temperature ～800 °C) and fine-grained microstructure (～276 nm). The newly developed SiC-TiC composite exhibited a ～2-fold increase in nominal strain as compared to that of monolithic SiC. The plastic deformation caused by grain-boundary sliding in monolithic SiC was supplemented by the plastic deformation of TiC in the SiC-TiC composite. The hot-forged composite exhibited anisotropy in its microstructure and mechanical and thermal properties due to the preferred alignment of α-SiC platelets formed in situ. The relative density, flexural strength, fracture toughness, and thermal conductivity of the composite increased from 98.4 %, 608 MPa, 5.1 MPa?m^1/2, and 34.6 Wm^?1 K^?1 in the as-sintered specimen to 99.9 %, 718–777 MPa, 6.9–7.8 MPa?m^1/2, and 54.8–74.7 Wm^?1 K^?1, respectively, on hot forging.     

Thermal and electrical conductivity of melt mixed polycarbonate hybrid composites co‐filled with multi‐walled carbon nanotubes and graphene nanoplatelets

In this work, we present thermoplastic nanocomposites of polycarbonate (PC) matrix with hybrid nanofillers system formed by a melt‐mixing approach. Various concentrations of multi‐walled carbon nanotubes (MWCNT) and graphene nanoplatelets (GnP) were mixed in to PC and the melt was homogenized. The nanocomposites were compression molded and characterized by different techniques. Torque dependence on the nanofiller composition increased with the presence of carbon nanotubes. The synergy of carbon nanotubes and GnP showed exponential increase of thermal conductivity, which was compared to logarithmic increase for nanocomposite with no MWCNT. Decrease of Shore A hardness at elevated loads present for all investigated nanocomposites was correlated with the expected low homogeneity caused by a low shear during melt‐mixing. Mathematical model was used to calculate elastic modulus from Shore A tests results. Vicat softening temperature (VST) showed opposite pattern for hybrid nanocomposites and for PC‐MWCNT increasing in the latter case. Electrical conductivity boost was explained by the collective effect of high nanofiller loads and synergy of MWCNT and GnP. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42536.     

The effect of surface treatment on graphite nanoplatelets used in fiber reinforced composites

Atmospheric plasma treatment (APT) was used to surface‐activate graphite nanoplatelets (GnP) as well as highly graphitic P100 fibers used to manufacture composites. X‐ray photoelectron spectroscopy showed an increase in the O/C ratio of the treated surfaces when using either CO or O₂ as the active gas, whereas CO exhibited less damage to the treated reinforcement carbon material. APT of P100 fibers resulted in a 75% increase in composite tensile strength when compared to composites using untreated fibers. Surface treatment of GnPs also resulted in GnP/epoxy composites with significantly higher glass transition temperatures (Tg's) and 50% higher flexural strengths than those with no surface treatment because of stronger particle‐to‐resin coupling, which was also evidenced by the fracture surfaces. The effect of GnP loading concentration and plasma treatment duration was also evaluated on the tensile strength of fiber‐reinforced composites. The addition of untreated GnP filler resulted in a decrease in strength up to the 1% loading. However, higher loading conditions resulted in a 20% improvement because of GnP orientation effects. Fracture surfaces suggest that the fibers provided a mechanism for the GnPs to orient themselves parallel to the fiber axis, developing an oriented matrix microstructure that contributes to added crack deflection. Incorporating surface‐treated GnPs in these composites resulted in tensile strengths that were as high as 50% stronger than the untreated systems for all loading conditions. Increased GnP‐to‐matrix bonding as well as enhanced orientation of the GnPs resulted in multifunctional composites with improved mechanical performance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39994.     

Reinforcing effect of amine-functionalized and carboxylated porous graphene on toughness,thermal stability,and electrical conductivity of epoxy-based nanocomposites

Epoxy-based nanocomposites reinforced with nonfunctionalized porous graphene (NPG), carboxylated porous graphene (CNPG), and amine-functionalized porous graphene (ANPG) were investigated with regard to mechanical properties, thermal stability, and electrical conductivity. Nanomaterials were added to the epoxy matrix in varying contents of 0.5, 1, and 2 wt %. Generally, mechanical properties were improved as a result of introducing nanomaterials into the epoxy resin. However, the amelioration of toughness was only observed in functionalized NPGs/epoxy nanocomposites. Field emission scanning electron microscopy images showed that functionalized nanomaterials induced a rougher fracture surface compared to the neat epoxy. Dynamic mechanical analysis along with differential scanning calorimetry confirmed an increment in the glass-transition temperature (T_g) of the reinforced nanocomposites. Also, they proved that functionalization made the epoxy network tougher and more flexible. The electrical conductivity and thermal stability of the epoxy resin were also improved when loaded with nanomaterials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47475.