Graphene and carbon nanotube reinforced epoxy nanocomposites: A review

Epoxy/Graphene Nanoplatelet (GNP) Nanocomposites: An Experimental Study on Tensile, Compressive, and Thermal Properties

This paper presents an experimental investigation of nanocomposites composed of three ratios of epoxy/graphene nanoplatelets (GNPs) by weight. The 0.1, 0.2, and 0.3 wt.% specimens were carefully manufactured, and their mechanical and thermal conductivity properties were examined. The tensile strength and modulus of epoxy/GNPs were enhanced by the large surface area of graphene nanoplatelets, causing crack deflection that created new fracture fronts and friction because of the rough fracture surface. However, the compressive strength was gradually reduced as GNP loading percentages increased. This was probably due to severe plastic yielding on the epoxy, leading to catastrophic axial splitting caused by premature fractures. Furthermore, the highest thermal conductivity was 0.1283 W/m-K, representing a 20.92% improvement over neat epoxy (0.1061 W/m-K) when 0.3 wt.% GNPs were added to the epoxy. This was because of efficient heat propagation in the GNPs due to electron movement through percolative paths. The tensile failure mode in epoxy/GNP nanocomposites showed a few deflected and bifurcated rough cracks and brittle, dimple-like fractures. Contrarily, compressive failure mode in GNP-added epoxy showed plastic flexural buckling and brittle large-axial splitting. The epoxy/GNP nanocomposites were considered a damage-tolerant material.

Carbon nanotube nanocomposite scaffolds: advances in fabrication and applications for tissue regeneration and cancer therapy

Carbon nanotube (CNT) nanocomposite scaffolds have emerged as highly promising frameworks for tissue engineering research. By leveraging their intrinsic electrical conductivity and valuable mechanical properties, CNTs are commonly dispersed into polymers to create robust, electrically conductive scaffolds that facilitate tissue regeneration and remodeling. This article explores the latest progress and challenges related to CNT dispersion, functionalization, and scaffold printing techniques, including electrospinning and 3D printing. Notably, these CNT scaffolds have demonstrated remarkable positive effects across various cell culture systems, stimulating neuronal growth, promoting cardiomyocyte maturation, and facilitating osteocyte differentiation. These encouraging results have sparked significant interest within the regenerative medicine field, including neural, cardiac, muscle, and bone regenerations. However, addressing the concern of CNT cytotoxicity in these scaffolds remains critical. Consequently, substantial efforts are focused on exploring strategies to minimize cytotoxicity associated with CNT-based scaffolds. Moreover, researchers have also explored the intriguing possibility of utilizing the natural cytotoxic properties of CNTs to selectively target cancer cells, opening up promising avenues for cancer therapy. More research should be conducted on cutting-edge applications of CNT-based scaffolds through phototherapy and electrothermal ablation. Unlike drug delivery systems, these novel methodologies can combine 3D additive manufacturing with the innate physical properties of CNT in response to electromagnetic stimuli to efficiently target localized tumors. Taken together, the unique properties of CNT-based nanocomposite scaffolds position them as promising candidates for revolutionary breakthroughs in both regenerative medicine and cancer treatment. Continued research and innovation in this area hold significant promise for improving healthcare outcomes.

Development of an Electroactive and Thermo-Reversible Diels-Alder Epoxy Nanocomposite Doped with Carbon Nanotubes

The manufacturing of Diels-Alder (D-A) crosslinked epoxy nanocomposites is an emerging field with several challenges to overcome: the synthesis is complex due to side reactions, the mechanical properties are hindered by the brittleness of these bonds, and the content of carbon nanotubes (CNT) added to achieve electroactivity is much higher than the percolation thresholds of other conventional resins. In this work, we develop nanocomposites with different D-A crosslinking ratios (0, 0.6, and 1.0) and CNT contents (0.1, 0.3, 0.5, 0.7, and 0.9 wt.%), achieving a simplified route and avoiding the use of solvents and side reactions by selecting a two-step curing method (100 °C-6 h + 60 °C-12 h) that generates the thermo-reversible resins. These reversible nanocomposites show ohmic behavior and effective Joule heating, reaching the dissociation temperatures of the D-A bonds. The fully reversible nanocomposites (ratio 1.0) present more homogeneous CNT dispersion compared to the partially reversible nanocomposites (ratio 0.6), showing higher electrical conductivity, as well as higher brittleness. For this study, the nanocomposite with a partially reversible matrix (ratio 0.6) doped with 0.7 CNT wt.% was selected to allow us to study its new smart functionalities and performance due to its reversible network by analyzing self-healing and thermoforming.

Ionic Liquids as Alternative Curing Agents for Conductive Epoxy/CNT Nanocomposites with Improved Adhesive Properties

Good dispersion of carbon nanotubes (CNTs) together with effective curing were obtained in epoxy/CNT nanocomposites (NCs) using three different ionic liquids (ILs). Compared to conventional amine-cured epoxy systems, lower electrical percolation thresholds were obtained in some of the IL-based epoxy systems. For example, the percolation threshold of the trihexyltetradecylphosphonium dicyanamide (IL-P-DCA)-based system was 0.001 wt.%. The addition of CNTs was not found to have any significant effect on the thermal or low-strain mechanical properties of the nanocomposites, but it did improve their adhesive properties considerably compared to the unfilled systems. This study demonstrates that ILs can be used to successfully replace traditional amine-based curing agents for the production of electrically conductive epoxy/CNT NCs and adhesives, as a similar or better balance of properties was achieved. This represents a step towards greater sustainability given that the vapor pressure of ILs is low, and the amount needed to effectively cure epoxy resins is significantly lower than any of their counterparts.

CNT-Reinforced Self-Healable Epoxy Dynamic Networks Based on Disulfide Bond Exchange

The design and utilization of polymers with healing capability have drawn increasing attention owing to their enhanced chain mobility and opportunity to heal minor cracks in composites. Rehealable thermoset polymers promise reduction in the maintenance cost and thus prolonged lifetime, reshaping, and recyclability. Introducing reversible covalent bonds is the mainstay strategy to achieve such plasticity in crosslinked polymers. Herein, we report a dynamic epoxy, which includes associative covalent adaptive networks (CANs) based on disulfide exchange bonds. Epoxy resin is chosen to study rehealing, as it is one of the most critical thermosetting polymers for various industries from aerospace to soft robotics. This study enlightens us about not only the consequences of CANs in the epoxy but also various factors such as soft segments and carbon nanotubes (CNTs). Epoxy dynamic networks are investigated in an attempt to explore the synergistic effect of the soft-segmented resins and CNTs on the healing and reshaping characteristics of epoxy networks along with varying stiffness. This research discusses epoxy dynamic networks in three main aspects: crosslink density, CAN density, and CNTs. Introducing soft segments into the epoxy network enhances the healing efficiency due to the increased chain mobility. A higher CAN density accelerates network rearrangement, improving the healing efficiency. It should also be noted that even with a low weight fraction of nanotubes, CNT-reinforced samples restored their initial strength more than neat samples after healing. The tensile strength of dynamic networks is at least 50 MPa, which is significant for their utility in primary or secondary structural components.

Fabrication of a Novel (PVDF/MWCNT/Polypyrrole) Antifouling High Flux Ultrafiltration Membrane for Crude Oil Wastewater Treatment

The present work deals with the fabrication of novel poly(vinylidene fluoride) (PVDF)/Multi-wall Carbon Nanotubes (MWCNT)/Polypyrrole (PPy) ultrafiltration membrane by phase inversion technique for the removal of crude oil from refinery wastewater. In situ polymerization of pyrrole with different concentrations of MWCNT ranging from 0.025 wt.% to 0.3 wt.% in PVDF prepared solutions. Measurement of permeability, porosity, contact angle, tensile strength, zeta potential, rejection studies and morphological characterization by scanning electron microscopy (SEM) were conducted. The results showed that membrane with (0.05% MWCNT) concentration had the highest permeability flux (850 LMH/bar), about 17 folds improvement of permeability compared to pristine PVDF membrane. Moreover, membrane rejection of crude oil reached about 99.9%. The excellent performance of this nanocomposite membrane suggests that novel PVDF modification with polypyrrole had a considerable effect on permeability with high potential for use in the treatment of oily wastewater in the refinery industry.

Epoxy resin reinforced with graphene derivatives: physical and dielectric properties

Epoxy resins are important industrial polymers due to their versatile properties and ease of preparation. They are used on a large scale in coating and adhesives applications. Epoxy resins are prepared by photo-curing technique or thermal curing method in presence of different hardeners. The first method is used for small areas while the latter is utilized mainly for coating applications. Graphene and its oxide have proved themselves as good fillers for epoxy resin since the formed composites demonstrated enhanced mechanical, thermal and electrical properties. This article gives insight view for synthesis techniques and properties of these composites with a deep discussion for electrical and dielectric investigations of epoxy resins loaded with threshold concentration of graphene oxide. A case study of dielectric properties of epoxy resin/modified graphene oxide composite, is presented in which effect of curing technique on dielectric behavior is explored. Although the amount of filler was kept at the threshold concentration (1% by weight) obvious change in the dielectric properties could be observed unlike the rest of properties.

Glass transition of nanometric polymer films probed by picosecond ultrasonics

The possibility to measure the glass transition temperature in poly(methyl methacrylate) (PMMA) films by picosecond ultrasonics with thicknesses ranging from 458 nm to 32 nm is demonstrated. A shift of the longitudinal acoustic eigenmodes towards lower frequencies with temperature is observed accompanied by a change in the temperature-frequency slopes at the glass transition temperature. The contributions to the frequency shift from changes in film thickness and sound velocity are discussed and the latter is extracted below the glass transition temperature. Finally, the advantages and disadvantages of the current approach in a comparison to other methods based on acoustic measurements in the GHz regime are reviewed.

The Influence of Sonication Processing Conditions on Electrical and Mechanical Properties of Single and Hybrid Epoxy Nanocomposites Filled with Carbon Nanoparticles

Graphene nanoplatelets (GNP) and carbon nanotubes (CNT) are used to enhance electrical and mechanical properties of epoxy-based nanocomposites. Despite the evidence of synergetic effects in the hybrid GNP-CNT-epoxy system, there is still a lack of studies that focus on the influence of different dispersion methods on the final properties of these ternary systems. In the present work, direct and indirect ultrasonication methods were used to prepare single- and hybrid-filled GNP-CNT-epoxy nanocomposites, varying the amplitude and time of sonication in order to investigate their effect on electrical and thermomechanical properties. Impedance spectroscopy was combined with rheology and electron microscopy to show that high-power direct sonication tends to degrade electrical conductivity in GNP-CNT-epoxy nanocomposites due to damage caused in the nanoparticles. CNT-filled samples were mostly benefitted by low-power direct sonication, achieving an electrical conductivity of 1.3 × 10⁻³ S·m⁻¹ at 0.25 wt.% loading, while indirect sonication was not able to properly disperse the CNTs and led to a conductivity of 1.6 ± 1.3 × 10⁻⁵. Conversely, specimens filled with 2.5 wt. % of GNP and processed by indirect sonication displayed an electrical conductivity that is up to 4 orders of magnitude higher than when processed by direct sonication, achieving 5.6 × 10⁻⁷ S·m⁻¹. The introduction of GNP flakes improved the dispersion state and conductivity in hybrid specimens processed by indirect sonication, but at the same time impaired these properties for high-power direct sonication. It is argued that this contradictory effect is caused by a selective localization of shorter CNTs onto GNPs due to strong π-π interactions when direct sonication is used. Dynamic mechanical analysis showed that the addition of nanofillers improved epoxy’s storage modulus by up to 84%, but this property is mostly insensitive to the different processing parameters. Decrease in crosslinking degree and presence of residual solvent confirmed by Fourier-transform infrared spectroscopy, however, diminished the glass transition temperature of the nanocomposites by up to 40% when compared to the neat resin due to plasticization effects.

Disperse-and-Mix: Oil as an 'Entrance Door' of Carbon-Based Fillers to Rubber Composites

Oil was employed as an ‘entrance door’ for loading rubber with carbon-based fillers of different size and dimensionalities: 1D carbon nanotubes (CNTs), 2D graphene nanoplatelets (GNPs), and 3D graphite. This approach was explored, as a proof of concept, in the preparation of tire tread, where oil is commonly used to reduce the viscosity of the composite mixture. Rubber was loaded with carbon black (CB, always used) and one or more of the above fillers to enhance the thermal and mechanical properties of the composite. The CNT-loaded system showed the best enhancement in mechanical properties, followed by the CNT-GNP one. Rubber loaded with both graphite and GNP showed the best enhancement in thermal conductivity (58%). The overall enhancements in both mechanical and thermal properties of the various systems were analyzed through an overall relative efficiency index in which the total filler concentration in the system is also included. According to this index, the CNT-loaded system is the most efficient one. The oil as an ‘entrance door’ is an easy and effective novel approach for loading fillers that are in the nanoscale and provide high enhancement of properties at low filler concentrations.

Thermal Degradation Behavior of Epoxy Resin Containing Modified Carbon Nanotubes

Via the surface-grafting of carbon nanotubes (CNTs) with a silicon-containing flame retardant (PMDA), a novel flame retardant CNTs-PMDA was synthesized. The flame retardancy was tested by cone calorimeter. Compared with pure epoxy resin, the total heat release (THR) and peak heat release rate (PHRR) of epoxy resin containing CNTs-PMDA were significantly reduced, by 44.6% and 24.6%, respectively. Furthermore, thermal degradation behavior of epoxy resin based composite was studied by the thermogravimetric analysis with differences in heating rates. The kinetic parameters of the thermal degradation for epoxy resin composites were evaluated by the Kissinger method and Flynn-Wall-Ozawa method. The results suggested that activation energy values of epoxy resin containing CNTs-PMDA in thermal degradation process were higher than those of pure epoxy resin in the final stage of the thermal degradation process, which was closely related to the final formation of char layer residues. Finally, the results from Dynamic mechanical thermal analysis (DMTA) and Scanning electron microscopy (SEM) measurements exhibited that the functionalization of CNTs with PMDA obviously improved the dispersion of CNTs in the epoxy resin matrix.

Ice-Prevention and De-Icing Capacity of Epoxy Resin Filled with Hybrid Carbon-Nanostructured Forms: Self-Heating by Joule Effect

In this study, CNTs and graphite have been incorporated to provide electrical conductivity and self-heating capacity by Joule effect to an epoxy matrix. Additionally, both types of fillers, with different morphology, surface area and aspect ratio, were simultaneously incorporated (hybrid CNTs and graphite addition) into the same epoxy matrix to evaluate the effect of the self-heating capacity of carbon materials-based resins on de-icing and ice-prevention capacity. The self-heating capacity by Joule effect and the thermal conductivity of the differently filled epoxy resin were evaluated for heating applications at room temperature and at low temperatures for de-icing and ice-prevention applications. The results show that the higher aspect ratio of the CNTs determined the higher electrical conductivity of the epoxy resin compared to that of the epoxy resin filled with graphite, but the 2D morphology of graphite produced the higher thermal conductivity of the filled epoxy resin. The presence of graphite enhanced the thermal stability of the filled epoxy resin, helping avoid its deformation produced by the softening of the epoxy resin (the higher the thermal conductivity, the higher the heat dissipation), but did not contribute to the self-heating by Joule effect. On the other hand, the feasibility of electrically conductive epoxy resins for de-icing and ice-prevention applications by Joule effect was demonstrated.

Trimetallic@Cyclodextrin Nanocomposite: Photocatalyst for Degradation of Amoxicillin and Catalyst for Esterification Reactions

The industry is looking for new materials which can respond to specific applications that exclusively advance materials can provide. In this context, nanoparticles and nanocomposites opened an interesting method for designing specific properties which can be modulated according to the requirements. The preparation of biomolecules supported trimetallic nanoparticles and some other derives is a good example of the complex systems that can be designed for getting exclusive properties. This study is based on the preparation of new cyclodextrin supported Fe/La/Zn trimetallic nanocomposite by the microemulsion technique. Photocatalytic degradation of amoxicillin was performed using cyclodextrin-Fe/La/Zn. 78% of amoxicillin photodegradation along 4 hours of photoirradiation was achieved. Finally, the catalytic nature of new material was explored for oxidation and esterification reactions. The present study revealed that this advanced multifunctional nanomaterial can be successfully employed for environmental remediation and catalytic activities.

Investigating Physio-Thermo-Mechanical Properties of Polyurethane and Thermoplastics Nanocomposite in Various Applications

The effect of the soft and hard polyurethane (PU) segments caused by the hydrogen link in phase-separation kinetics was studied to investigate the morphological annealing of PU and thermoplastic polyurethane (TPU). The significance of the segmented PUs is to achieve enough stability for further applications in biomedical and environmental fields. In addition, other research focuses on widening the plastic features and adjusting the PU-polyimide ratio to create elastomer of the poly(urethane-imide). Regarding TPU- and PU-nanocomposite, numerous studies investigated the incorporation of inorganic nanofillers such as carbon or clay to incorporating TPU-nanocomposite in several applications. Additionally, the complete exfoliation was observed up to 5% and 3% of TPU-clay modified with 12 amino lauric acid and benzidine, respectively. PU-nanocomposite of 5 wt.% Cloisite®30B showed an increase in modulus and tensile strength by 110% and 160%, respectively. However, the nanocomposite PU-0.5 wt.% Carbone Nanotubes (CNTs) show an increase in the tensile modulus by 30% to 90% for blown and flat films, respectively. Coating PU influences stress-strain behavior because of the interaction between the soft segment and physical crosslinkers. The thermophysical properties of the TPU matrix have shown two glass transition temperatures (Tg's) corresponding to the soft and the hard segment. Adding a small amount of tethered clay shifts Tg for both segments by 44 °C and 13 °C, respectively, while adding clay from 1 to 5 wt.% results in increasing the thermal stability of TPU composite from 12 to 34 °C, respectively. The differential scanning calorimetry (DSC) was used to investigate the phase structure of PU dispersion, showing an increase in thermal stability, solubility, and flexibility. Regarding the electrical properties, the maximum piezoresistivity (10 S/m) of 7.4 wt.% MWCNT was enhanced by 92.92%. The chemical structure of the PU-CNT composite has shown a degree of agglomeration under disruption of the sp2 carbon structure. However, with extended graphene loading to 5.7 wt.%, piezoresistivity could hit 10-1 S/m, less than 100 times that of PU. In addition to electrical properties, the acoustic behavior of MWCNT (0.35 wt.%)/SiO2 (0.2 wt.%)/PU has shown sound absorption of 80 dB compared to the PU foam sample. Other nanofillers, such as SiO2, TiO2, ZnO, Al2O3, were studied showing an improvement in the thermal stability of the polymer and enhancing scratch and abrasion resistance.

Thermal conductivity and mechanical performance of hexagonal boron nitride nanosheets-based epoxy adhesives

Thermosets possess diverse physical and chemical properties and thus they are widely used in various applications such as electronic packaging, construction, and automotive industries. However, their poor thermal conductivity and weak mechanical performance jeopardize their continual spread in modern industry. In this study, boron nitride nanosheets (BNNSs) were employed to promote both mechanical and thermal properties of epoxy nanocomposites. BNNSs and their epoxy nanocomposites were fabricated usingin situsolvent ultrasonication andin situpolymerization, respectively. Thermal conductivity was enhanced by 153% increment in epoxy/BNNS nanocomposite at 7 wt% in comparison with neat epoxy. In parallel, Young's modulus, lap shear strength, fracture toughness (K_1C) and energy release rate (G_1C) increased by 69%, 31%, 122% and 118%, respectively at 1 wt% BNNSs. Moreover, fatigue life and strength of lap shear joints were significantly improved upon adding BNNSs. A numerical model of the single lap shear joint was developed to validate the accuracy of the material constants obtained. Epoxy/BNNS nanocomposites exhibited an outstanding mechanical performance as well as high thermal conductivity giving them merits to widen their applications in electronic and automotive industry.

A Suggested Vacuum Bagging Process for the Fabrication of Single-Walled Carbon Nanotube/Epoxy Composites That Maximize Electromagnetic Interference Shielding Effectiveness

We designed and tested a manufacturing process that resulted in the formation of composites with maximized electrical conductivity and optimized electromagnetic interference (EMI) shielding effectiveness (SE) properties. Single-walled carbon nanotube (SWCNT) paper, which is a microscopic aggregate of van der Waals force interaction, was impregnated with semi-cured epoxy to make SWCNT prepregs. These prepregs were completely cured into SWCNT/epoxy composites. Fabricating and curing processes were executed under proper temperature cycle depending on the time. We inspected SWCNT paper and the interfacial state between the SWCNTs and epoxy in the composite with a field emission-scanning electron microscopy and calculated the SWCNT weight fraction through thermogravimetric analysis measurements. Using these observations, electrical conductivity and EMI SE were investigated according to thickness which could be controlled by the suggested manufacturing process as 1-, 5- and 10-layer composites. Finally, we determined ideal composite thickness and the associated number of prepreg layers using skin depth theory.

Mechanical properties of aerospace epoxy composites reinforced with 2D nano-fillers: current status and road to industrialization

High-performance epoxy composites find application in the aerospace industry. Although epoxy is a high-performance polymer, its fracture toughness is compromised due to its highly cross-linked nature. Nanomaterials such as carbon nanotubes (CNTs), graphene derivatives, and inorganic 2-dimensional (2D) nanomaterials are being explored to improve epoxy composites' mechanical properties. Graphene is one of the most popular 2D nano-reinforcing agents for epoxy composites. Following graphene discovery, the research community's attention was brought to various other few-atom thick 2D nanomaterials. Hence, apart from graphene, inorganic nanosheets such as transition metal dichalcogenides (TMDs), hexagonal boron nitride (hBN), etc., are also being studied as modifiers for enhancing the mechanical performance of epoxy composites. Graphene, TMDs and hBN are known to possess a high aspect ratio, high specific surface area and inherently high mechanical strength and stiffness, contributing to a stronger and tougher composite. Despite that, the challenges associated with these nanomaterials, such as dispersion issues, lack of standardization, underlying health hazards, etc., have hampered their commercialization. It has been long past a decade since the discovery of graphene, yet there are concerns regarding the lab to industry scale-up, and health and environmental hazards associated with nanomaterials for the fabrication of aerospace composites. This review offers a comprehensive literature survey and a perspective into the possible ways of bridging the gaps between the laboratory research and industrialization of 2D nanosheet-filled epoxy composites.

Silicone Composites with CNT/Graphene Hybrid Fillers: A Review

This review is dedicated to versatile silicone rubber composites based on carbon nanotube/graphene (CNT/G) hybrid fillers. Due to their unique mechanical, electrical, thermal, and biological properties, such composites have enormous potential for medical, environmental, and electronics applications. In the scope of this paper, we have explored CNT/graphene/silicone composites with a different morphology, analyzed the synergistic effect of hybrid fillers on various properties of silicone composites, and observed the existing approaches for the fabrication of hybrid composites with a seamless, assembled, and/or foamed structure. In conclusion, current challenges and future prospects for silicone composites based on CNTs and graphene have been thoroughly discussed.

Fabrication, Functionalization, and Application of Carbon Nanotube-Reinforced Polymer Composite: An Overview

A novel class of carbon nanotube (CNT)-based nanomaterials has been surging since 1991 due to their noticeable mechanical and electrical properties, as well as their good electron transport properties. This is evidence that the development of CNT-reinforced polymer composites could contribute in expanding many areas of use, from energy-related devices to structural components. As a promising material with a wide range of applications, their poor solubility in aqueous and organic solvents has hindered the utilizations of CNTs. The current state of research in CNTs-both single-wall carbon nanotubes (SWCNT) and multiwalled carbon nanotube (MWCNT)-reinforced polymer composites-was reviewed in the context of the presently employed covalent and non-covalent functionalization. As such, this overview intends to provide a critical assessment of a surging class of composite materials and unveil the successful development associated with CNT-incorporated polymer composites. The mechanisms related to the mechanical, thermal, and electrical performance of CNT-reinforced polymer composites is also discussed. It is vital to understand how the addition of CNTs in a polymer composite alters the microstructure at the micro- and nano-scale, as well as how these modifications influence overall structural behavior, not only in its as fabricated form but also its functionalization techniques. The technological superiority gained with CNT addition to polymer composites may be advantageous, but scientific values are here to be critically explored for reliable, sustainable, and structural reliability in different industrial needs.

Determination of mechanical properties of two-phase and hybrid nanocomposites: experimental determination and multiscale modeling

In this paper, the effects of filler content and the use of hybrid nanofillers on agglomeration and nanocomposite mechanical properties such as elastic moduli, ultimate strength and elongation to failure are investigated experimentally. In addition, thermoset epoxy-based two-phase and hybrid nanocomposites are simulated using multiscale modeling techniques. First, molecular dynamics simulation is carried out at nanoscale considering the interphase. Next, finite element method and micromechanical modeling are used for micro and macro scale modeling of nanocomposites. Nanocomposite samples containing carbon nanotubes, graphene nanoplatelets, and hybrid nanofillers with different filler contents are prepared and are tested. Also, field emission scanning electron microscopy is used to take micrographs from samples’ fracture surfaces. The results indicate that in two-phase nanocomposites, elastic modulus and ultimate strength increase while nanocomposite elongation to failure decreases with reinforcement weight fraction. In addition, nanofiller agglomeration occurred at high nanofiller contents especially higher than 0.75 wt% in the two-phase nanocomposites. Nanofiller agglomeration was observed to be much lower in the hybrid nanocomposite samples. Therefore, using hybrid nanofillers delays/prevents agglomeration and improves mechanical properties of nanocomposite at the same total filler content.

Temperature-Dependent Synergistic Effect of Multi-Walled Carbon Nanotubes and Graphene Nanoplatelets on the Tensile Quasi-Static and Fatigue Properties of Epoxy Nanocomposites

Even though the characteristics of polymer materials are sensitive to temperature, the mechanical properties of polymer nanocomposites have rarely been studied before, especially for the fatigue behavior of hybrid polymer nanocomposites. Hence, the tensile quasi-static and fatigue tests for the epoxy nanocomposites reinforced with multi-walled carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) were performed at different temperatures in the study to investigate the temperature-dependent synergistic effect of hybrid nano-fillers on the studied properties. The temperature and the filler ratio were the main variables considered in the experimental program. A synergistic index was employed to quantify and evaluate the synergistic effect of hybrid fillers on the studied properties. Experimental results show that both the monotonic and fatigue strength decrease with increasing temperature significantly. The nanocomposites with a MWCNT (multi-walled CNT): GNP ratio of 9:1 display higher monotonic modulus/strength and fatigue strength than those with other filler ratios. The tensile strengths of the nanocomposite specimens with a MWCNT:GNP ratio of 9:1 are 10.0, 5.5, 12.9, 23.4, and 58.9% higher than those of neat epoxy at -28, 2, 22, 52, and 82 °C, respectively. The endurance limits of the nanocomposites with this specific filler ratio are increased by 7.7, 26.7, 5.6, 30.6, and 42.4% from those of pristine epoxy under the identical temperature conditions, respectively. Furthermore, the synergistic effect for this optimal nanocomposite increases with temperature. The CNTs bridge the adjacent GNPs to constitute the 3-D network of nano-filler and prevent the agglomeration of GNPs, further improve the studied strength. Observing the fracture surfaces reveals that crack deflect effect and the bridging effect of nano-fillers are the main reinforcement mechanisms to improve the studied properties. The pullout of nano-fillers from polymer matrix at high temperatures reduces the monotonic and fatigue strengths. However, high temperature is beneficial to the synergistic effect of hybrid fillers because the nano-fillers dispersed in the softened matrix are easy to align toward the directions favorable to load transfer.

Epoxy Resin Nanocomposites: The Influence of Interface Modification on the Dispersion Structure—A Small-Angle-X-ray-Scattering Study

The surface functionalization of inorganic nanoparticles is an important tool for the production of homogeneous nanocomposites. The chemical adaptation of the nano-filler surface can lead to effective weak to strong interactions between the fillers and the organic matrix. Here we present a detailed systematic study of different surface-functionalized particles in combination with a SAXS method for the systematic investigation of the interface interaction in the development of epoxy nanocomposites. We investigated the effect of surface modification of spherical SiO2 nanoparticles with 9 nm and 72 nm diameter and crystalline ZrO2 nanoparticles with 22 nm diameter on the homogeneous distribution of the fillers in diethylenetriamine (DETA) cured bisphenol-F-diglycidylether epoxy resin nanocomposites. Unmodified nanoparticles were compared with surface-modified oxides having diethylene glycol monomethyl ethers (DEG), 1,2-diols, or epoxy groups attached to the surface. The influence of surface modification on dispersion quality was investigated by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) for inorganic filler contents of 3, 5 and 10 wt%. It was shown that the dispersion quality can be optimized by varying the coupling agent end group to obtain homogeneous and transparent nanomaterials. UV/VIS measurements confirmed the transparency/translucency of the obtained materials. The relationship between particle–matrix interaction and particle–particle interaction plays a decisive role in homogeneity and is controlled by the surface groups as well as by the type, size, and morphology of the nanoparticles themselves.

Effect of MWCNTs on Wear Behavior of Epoxy Resin for Aircraft Applications

The aim of the study is to assess the effect of multi-walled carbon nanotubes (MWCNTs) on the wear behavior of MWCNT-doped epoxy resin. In this study, a laminating resin system designed to meet the standards for motor planes was modified with MWCNTs at mass fractions from 0.0 wt.% to 2.0 wt.%. The properties of the carbon nanotubes were determined in Raman spectroscopy and HR-TEM. An examination of wear behavior was conducted on a linear abraser with a visual inspection on an optical microscope and SEM imaging, mass loss measurement, and evaluation of the wear volume on a profilometer. Moreover, the mechanical properties of MWCNTs/epoxy nanocomposite were evaluated through a tensile test and Shore D hardness test. The study shows that the best wear resistance is achieved for the mass percentage between 0.25 wt.% and 0.5 wt.%. For the same range, the tensile strength reaches the highest values and the hardness the lowest values. Together with surface imaging and a topography analysis, this allowed describing the wear behavior in the friction node and the importance of the properties of the epoxy nanocomposite.