Graphene-based Polymer Research Articles

Achieving high electrothermal and mechanical performance for Graphene/Poly(hexamethylene terephthalamide) composite films via interfacial engineering with two-dimensional polyarylamide nanosheets

Although graphene-based polymer electrothermal films have received great attention, the graphene aggregation restricts the improvement in electrothermal performance. This study reports graphene (GN)/two-dimensional polyarylamide nanosheets (2DPA) filled poly (hexamethylene terephthalamide) (PA6T) composite film with outstanding electrothermal and mechanical performance. Owing to the addition of 2DPA, the as-prepared 2DPA-GN/PA6T composite film can attain a high heating-up rate of 25.5 °C/s, 1.8 times higher than that of GN/PA6T composite film (14.1 °C/s). Furthermore, the 2DPA-modified composite film showed a remarkable heating temperature rise to ∼230 °C, 80 °C higher than that of GN/PA6T composite film (∼150 °C). Additionally, the film had excellent mechanical performance with tensile strength and modulus of elasticity of 32.5 MPa and 4.6 GPa, which were 24.2 % and 52.3 % higher than that of GN/PA6T composite film, respectively. Such outstanding performance came from strong interfacial adhesion between GN and PA6T, induced by 2DPA nanosheets through hydrogen bonding and π-π interactions, which were confirmed by FTIR and UV–Vis measurements. Besides improving interfacial adhesion, 2DPA can also reduce the surface defect density of the GN through π-π conjugation. Both improved interfacial adhesion and reduced defects of GN contributed to the formation of electrically conductive and stress transfer pathways, which supported the excellent electrothermal and mechanical properties of 2DPA-GN/PA6T composite films. This study demonstrates an effective way to prepare high-performance graphene composites for electrothermal applications, with expected uses in aerospace, industry, and other technological fields.

Drop-weight impact and compressive behavior of graphene-based carbon fiber-reinforced polymer composites

Drop-weight impact and compressive behavior of graphene-based carbon fiber-reinforced polymer composites

Unveiling transformative potential: recent advances in graphene-based polymer composites

Unveiling transformative potential: recent advances in graphene-based polymer composites

Intermolecular interactions in graphene and oxidized graphene nanocomposites

The spatial arrangement of graphene (G) or graphene oxide (GO) nanoplate agglomerations will significantly impact the material properties of graphene-based polymer nanocomposites. Therefore, we investigated the stability of G and GO agglomerates without the presence of a polymer network using molecular dynamics (MD) simulations, which was not considered in our previous work (Reil, 2022) [15]. G and GO nanoplates, often procured in powder forms, display a significant volume difference by visual observation. To this end, MD simulations were performed to model G or GO agglomerations in the powder form, including the effects of varied plate dimensions and localized surface oxidation. G plates on average released 231 kcal/mol upon agglomerating into aligned stacks, closely matching results in the literature. Simulations of GO resulted in agglomerations of clusters of plates rather than aligned stacks, releasing on average 16 % less energy than G. The clustered arrangement of GO plate agglomerates in simulations occupied a volume approximately 7x that of the aligned stack G plates, closely replicating the experimentally determined volume ratio of 10x. This research could yield further insight into the behavior of G and GO when in the presence of various polymer networks, which could be different than in isolation.

Graphene-based Polymer Composites in Thermal Management: Materials, Structures and Applications

Graphene, with its high thermal conductivity (k), excellent mechanical properties, and thermal stability, is an ideal filler for developing advanced high k and heat dissipation materials. However, creating graphene-based polymer...

Anti-corrosion and flame-retardant properties of environmentally benign smart functionalized WS2/rGO in epoxy coatings for enhanced steel structural protection in natural seawater

The epoxy matrix (EP) was filled with the rGO-APOD/WS2 nanofiller that was generated through mixing the surface-modified WS2 with reduced graphene oxide (rGO) and 2-amino-5-(4-aminophenyl)− 1, 3-oxadiazole (APOD). The effectiveness of epoxy coating on mild steel as a barrier against various concentrations of rGO-APOD/WS2 in naturally occurring seawater was assessed using EIS, SECM, and salt spray tests. In order to achieve the best coating performance, it was found that the optimal weight ratio of rGO-APOD/WS2 in the EP matrix was 0.3. The limiting oxygen index (LOI) test showed that the rGO-APOD/WS2 considerably enhanced the flame retardancy properties of the epoxy coating. In comparison to pure epoxy coating, the EP-rGO/APOD-WS2 demonstrated better flame retardancy with considerable reductions in the values of PHRR and THR, i.e., 81% and 70%, respectively. It was discovered that the coating resistance of EP-rGO/APOD-WS2 was much higher (Rcoat: 9.89E10 kΩ.cm2) than that of pure matrix (1.49E5 kΩ.cm2) after being exposed to natural seawater for one hour. The EIS experiments showed that the EP-rGO/APOD-WS2 nanocomposite had increased coating resilience even after 200 h of submersion in seawater. Because the coated substrate is more resistant to anodic dissipation than the uncoated substrate, SECM investigations showed that the least quantity of Fe2+ ions discharged at the scratch of the EP-rGO/APOD-WS2 coating. WS2 was found in rusted parts, producing an excellent inert layer at the surface, according to FE-SEM/EDX investigation. The newly created EP-rGO/APOD-WS2 composite has higher barrier and hydrophobic characteristics, according to the results (WCA:162°). The epoxy matrix's mechanical properties were enhanced by the addition of rGO/APOD-WS2. It was discussed how graphene-based polymer nanocomposites might prevent corrosion. As a result, an industrial coating made of the EP-rGO/APOD-WS2 nanocomposite may be used.

Graphite- and Graphene-Based Polymer Nanocomposites for Flexible Sensors and Actuators in Health Care and Soft Robotics Applications

Flexible sensors and actuators have broad applications in the fields of wearable electronics for health, sports, functional textiles, robotics and cobot applications. Graphene-or graphite-based polymer nanocomposites are promising materials for the development of soft sensors and actuators. This study investigates strain sensing properties of silicon rubber with various graphene filler concentrations (8wt%-12wt%). Current-voltage characteristics have been measured under various strains. We obtain that the sensor’s electrical resistance, for a given voltage, can be approximated by a linear fit of the logarithmic resistance as function of the extension ratio of the sensor. The obtained mechanically induced logarithmic resistor behavior of the polymer nanocomposite is highly promising for the development of electronic sensing and control. Furthermore, thin film graphite layers were investigated on highly stretchable silicone membranes.

Investigating the mechanical performance of graphene reinforced polymer nanocomposites via atomistic and continuum simulation approaches

Graphene, having exceptional mechanical properties, is expected to improve the overall mechanical performance of polymer nanocomposites when inserted as a nanofiller. In this work, the mechanical properties of graphene-based cis-1,4-polybutadiene glassy polymer nanocomposites are investigated via a hierarchical multiscale approach, combining atomistic simulations and continuum mechanics. The global mechanical properties of the graphene-based polymer nanocomposites are computed via a rich enough set of remote applied deformations. On a localized level, the effective Young's modulus and Poisson's ratio are calculated in both the interphase and polymer matrix regions where the former shows greater rigidity. Finally, the properties of the different phases forming the heterogeneous polymer nanocomposite are used to develop a continuum three-phase micromechanical finite element model for predicting the overall mechanical behavior of the structure, which are found to be in very good agreement with the results from the atomistic MD simulations.

Synthesis and Performance Evaluation of Graphene-Based Comb Polymer Viscosity Reducer

The high viscosity of heavy oil makes it difficult to realize its economic value. Therefore, improving the fluidity of heavy oil can effectively improve the economic benefit of the development of heavy oil resources. Oil-soluble viscosity reducers can utilize functional groups in monomers to break up asphaltene aggregates to improve the flow of crude oil. Graphene can be used to insert and split asphaltene aggregates through sliding phenomena and π–π interaction with colloidal asphaltene, thereby improving the fluidity of heavy oil. In this study, a graphene nanocomposite viscosity reducer was synthesized from lipophilic-modified graphene and a polymer viscosity reducer. The net viscosity reduction rate reached 80.0% at 400 ppm. Compared with a polymer viscosity reducer, the viscosity reduction effect of a graphene nanocomposite viscosity reducer was improved by about 7%. Structural characterization of a graphene nanocomposite viscosity reducer was characterized with infrared spectroscopy and a thermogravimetric test. The mechanism of a graphene nanocomposite viscosity reducer splitting asphaltene aggregates was verified with scanning electron microscopy. This study provides a theoretical and practical basis for the research and development of a novel nanocomposite viscosity reducer.

Fabrication of amino and fluorine functionalized graphene-based polymer composites to enhance the electromechanical conversion efficiency of TENGs for energy-harvesting applications

The two main factors hindering the practical utilization of triboelectric nanogenerators (TENGs) are low power density and high internal impedance. To address this issue, TENGs with high electromechanical conversion efficiency must be developed. Several techniques have been investigated to improve the TENGs output performance, including surface modifications (physical or chemical) and embedded charge-trap nanomaterials (dielectric or conductive). Herein, we introduce the novel amino-functionalized reduced graphene oxide (AFGO) and graphite-fluorinated polymer (FG) pillars to enhance the tribo-positivity and tribo-negativity of polyurethane (PU) and Ecoflex (EC), respectively. The surface positive-potential of PU is increased almost 2.2 times (from 201 V to 480 V) and negative-potential of Ecoflex is increased 2.1 times (from −848 V to −1813 V) with incorporating AFGO and FG pillars. Functionalized graphene and graphite-based pillars synergistically enhance surface charges (owing to the presence of –NH2 and -F terminating groups) and minimize triboelectric loss (owing to their conductive nature). The effects of the AFGO and FG contents on the electrical performance were studied systematically. The optimized PUAFGO2/EC15FG-TENG exhibited the maximum electrical output performance with an open-circuit potential of 434 V, a short-circuit current of 11. 2 µA, a power density of 1.18 Wm−2 at a load of 40 MΩ, and a charge density of 17.5 µCm−2. The PUAFGO2/EC15FG-TENG showed a mechanical conversion efficiency of 95% and successfully operated 33 LEDs and a stopwatch. Owing to this effectivity, even under low pressures, with a high sensitivity of 9.5 VPa−1 and high mechanical stability, the proposed TENG device could be used as a biomechanical energy harvester in the near future.

Mechanism of coupling polymer thickness and interfacial interactions on strength and toughness of non-covalent nacre-inspired graphene nanocomposites

Nanoconfinement resulting from interfacial attraction leads to the formation of polymer interphases with outstanding stiffness, which profoundly impacts the toughness and strength of non-covalent nacre-inspired nanocomposites with “brick-and-mortar” structures. Nonetheless, challenges arise due to discrepancies in interphase thickness characterization and ambiguity in nanoscopic foundations of interfacial stiffening, which hinders systematic understanding of strengthening and toughening mechanisms. To address these issues, we conduct coarse-grained molecular dynamics simulations to investigate the effect of polymer phase thickness and interfacial strength on the toughness and strength of graphene-polyethylene nanocomposites. Our results indicate that when the interfacial adhesion is equal to 0.12 J/m2, nanocomposites possessing a polyethylene phase thickness of 3 nm exhibit significantly greater yield strength (590.8 ± 3.3 MPa) than those of other thicknesses, while nanocomposites with polyethylene phase thickness of 13 nm exhibit the highest toughness (83.3 ± 1.7 MJ/m3). When the interfacial interaction adhesion increases from 0.12 to 1.75 J/m2, both the yield strength and toughness of nanocomposites with polymer thickness 3 nm experience a three-phase increase, reaching up to 1442.3 ± 107.7 MPa and 119.8 ± 8.4 MJ/m3, respectively. The aforementioned improvement in both strength and toughness can be attributed to the nanoconfinement originating from strong interfacial adhesion, which enhances the stiffness and strength of the polymer glues filling the gaps of graphene “bricks”. Furthermore, the deviation of the simulation results from the shear-lag model with mechanical properties of bulk polymer can be remedied with the nanoconfinement effect and polymer stretch taken into account. Our findings provide timely guidance for future design of non-covalent nacre-inspired graphene-based polymer nanocomposites with high toughness and strength.

Prevention of marine corrosion with graphene-based polymer coatings

Prevention of marine corrosion with graphene-based polymer coatings

Occupational Exposure during the Production and the Spray Deposition of Graphene Nanoplatelets-Based Polymeric Coatings.

Graphene-based polymer composites are innovative materials which have recently found wide application in many industrial sectors thanks to the combination of their enhanced properties. The production of such materials at the nanoscale and their handling in combination with other materials introduce growing concerns regarding workers' exposure to nano-sized materials. The present study aims to evaluate the nanomaterials emissions during the work phases required to produce an innovative graphene-based polymer coating made of a water-based polyurethane paint filled with graphene nanoplatelets (GNPs) and deposited via the spray casting technique. For this purpose, a multi-metric exposure measurement strategy was adopted in accordance with the harmonized tiered approach published by the Organization for Economic Co-operation and Development (OECD). As a result, potential GNPs release has been indicated near the operator in a restricted area not involving other workers. The ventilated hood inside the production laboratory guarantees a rapid reduction of particle number concentration levels, limiting the exposure time. Such findings allowed us to identify the work phases of the production process with a high risk of exposure by inhalation to GNPs and to define proper risk mitigation strategies.

Graphene-Based Polymer Nanocomposites Preparation and Their Advantages

Graphene and its derivatives have attracted the attention of researchers since its discovery due to its surprising properties. Since then, scientists have been trying to improve the processes that allow the incorporation of this material into polymeric matrices, to improve them, through the development of graphene-based polymeric nanocomposites. This review study reviewed these methods meticulously. Furthermore, it has already been cataloged that adding small amounts of graphene nano-fillers tends to improve the polymers’ mechanical, electrical, and thermal properties.

Dynamic diffusion of water inside graphene-reinforced PU/PTFE coatings: A molecular dynamics approach

Polymers are extensively used in various applications due to their excellent properties. Recently, graphene-based polymer composites have gotten significant attention due to their superior barrier properties to corrosive media. Although there are lots of experimental studies on graphene-based composites, there are very few works available at the atomistic level using molecular dynamics. The present work investigates the role of temperature on the diffusion of water and the effect of graphene-reinforcement in the polyurethane (PU) and polytetrafluoroethylene (PTFE). The results showed an increase in the diffusion at higher temperatures due to an increase in the mobility of polymeric chains at higher temperatures and hence a smooth path for the travel of water molecules. There is a significant decrease in the diffusion of water molecules in the graphene-reinforced systems when compared with neat PU and PTFE systems. The decrement in the diffusion of water in the range of 273 K to 350 K was around 79–93% for graphene-reinforce PU systems and around 58–62% in the case of graphene-reinforced PTFE systems.

Graphene-based polymer coatings for preventing marine corrosion: a review

Graphene-based polymer coatings for preventing marine corrosion: a review

Progressing of a power model for electrical conductivity of graphene-based composites

This work presents a power equation for the conductivity of graphene-based polymer composites by the tunneling length, interphase deepness and filler size. The impressions of these factors on the effective concentration and percolation beginning of graphene nano-sheets in nanocomposites are also expressed. The developed equations for percolation beginning and conductivity are examined by the experimented data of some examples, which can guesstimate the interphase depth, tunneling size and percolation exponent. Besides, the impacts of numerous factors on the percolation beginning and conductivity are designed. The developed equation for percolation beginning shows the formation of thick interphase and large tunnels in the reported samples. So, disregarding of tunneling and interphase spaces in polymer graphene nanocomposites overpredicts the percolation beginning. Additionally, the developed model presents the acceptable calculations for the conductivity of samples. Among the mentioned parameters, the concentration and graphene conductivity in addition to the interphase depth induce the strongest effects on the conductivity of composites.

Thermal behavior and thermolysis mechanisms of graphene oxide-intercalated energetic complexes of carbohydrazide

Graphene-based carbohydrazide coordination polymers are beneficial for improving solid propellants’ energy level and safety, so the study of their thermal decomposition mechanism is promoted for their wide application. In this paper, graphene oxide (GO) intercalated transition metal (Cu2+, Co2+, and Ni2+) complexes of carbohydrazide (CHZ) have been evaluated by using DSC/TGA apparatus and the TG-FTIR technique. Both isoconversional and combined kinetic methods were employed to calculate the kinetic parameters. The components inside GOCHZ-M would react with each other to cause a large mass loss rate and lead to a larger heat-releasing value than pure GO. The types of metal ions could affect their reaction model. Compared with GO, G-CHZ-Co shows a two-sided effect (stabilization and catalytic) on its decomposition. For G-CHZ-Co, the reaction model of each peak is close to the random 2d nucleation and nucleus growth model.

Crystallization and melting of polymer chains on graphene and graphene oxide.

This study employs all-atomistic (AA) molecular dynamics (MD) simulations to investigate the crystallization and melting behavior of polar and nonpolar polymer chains on monolayers of graphene and graphene oxide (GO). Polyvinyl alcohol (PVA) and polyethylene (PE) are used as representative polar and nonpolar polymers, respectively. A modified order parameter is introduced to quantify the degree of two-dimensional (2D) crystallization of polymer chains. Our results show that PVA and PE chains exhibit significantly different crystallization behavior. PVA chains tend to form a more rounded, denser, and folded-stemmed lamellar structure, while PE chains tend to form an elongated straight pattern. The presence of oxidation groups on the GO substrate reduces the crystallinity of both PVA and PE chains, which is derived from the analysis of modified order parameter. Meanwhile, the crystallization patterns of polymer chains are influenced by the percentage, chemical components, and distribution of the oxidation groups. In addition, our study reveals that 2D crystalized polymer chains exhibit different melting behavior depending on their polarity. PVA chains exhibit a more molecular weight-dependent melting temperature than PE chains, which have a lower melting temperature and are relatively insensitive to molecular weight. These findings highlight the critical role of substrate and chain polarity in the crystallization and melting of polymer chains. Overall, our study provides valuable insights into the design of graphene-based polymer heterostructures and composites with tailored properties.

Molecular Dynamics Simulations of the Mechanical Properties of Cellulose Nanocrystals-Graphene Layered Nanocomposites.

Cellulose nanocrystals (CNCs) have received a significant amount of attention due to their excellent physiochemical properties. Herein, based on bioinspired layered materials with excellent mechanical properties, a CNCs-graphene layered structure with covalent linkages (C-C bond) is constructed. The mechanical properties are systematically studied by molecular dynamics (MD) simulations in terms of the effects of temperature, strain rate and the covalent bond content. Compared to pristine CNCs, the mechanical performance of the CNCs-graphene layered structure has significantly improved. The elastic modulus of the layered structure decreases with the increase of temperature and increases with the increase of strain rate and covalent bond coverage. The results show that the covalent bonding and van der Waals force interactions at the interfaces play an important role in the interfacial adhesion and load transfer capacity of composite materials. These findings can be useful in further modeling of other graphene-based polymers at the atomic scale, which will be critical for their potential applications as functional materials.