Graphene-based Polymer Research Articles

Highly Thermally Conductive 3D Printed Graphene Filled Polymer Composites for Scalable Thermal Management Applications.

Efficient thermal transportation in a preferred direction is highly favorable for thermal management issues. The combination of 3D printing and two-dimensional (2D) materials such as graphene, BN, and so on enables infinite possibilities for hierarchically aligned structure programming. In this work, we report the formation of the asymmetrically aligned structure of graphene filled thermoplastic polyurethane (TPU) composites during 3D printing process. The as-printed vertically aligned structure demonstrates a through-plane thermal conductivity (TC) up to 12 W m-1 K-1 at 45 wt % graphene content, which is ∼8 times of that of a horizontally printed structure and surpasses many of the traditional particle reinforced polymer composites. The superior TC is mainly attributed to the anisotropic structure design that benefited from the preferable degree of orientation of graphene and the multiscale dense structure realized by finely controlling the printing parameters. Finite element method (FEM) confirms the essential impact of anisotropic TC design for highly thermal conductive composites. This study provides an effective way to develop 3D printed graphene-based polymer composites for scalable thermal-related applications such as battery thermal management, electric packaging, and so on.

Graphene Effect on Mechanical Properties of Sandwich Panel for Aerospace Structures

This research examines the mechanical properties of graphene-based polymer composites and Nomex honeycomb sandwich using a new strain sensing technique. Sandwich panels are fabricated individually with glass fibre reinforced polymers (GFRP) and face-sheets having different filler ratios of graphene nanoparticles (GNPs). These graphene nanoparticles are oxidized with (UV-O3) ozone to get graphene oxide (GO) which in turn improves resin matrix interfacial strength. Filler ratios of GO 0.0%, 0.2%, 0.6% and 1.0% by weight of poly-epoxy are fabricated for the face-sheets of composite sandwich panels. Graphene-based strain sensors are synthesized having a concentration of GNPs 5% by weight of polystyrene (PS). The strain sensors are pasted on the sandwich panels and four-point bending of the sandwich beams is performed to predict its flexural strength. The response of composite under different filler ratios of graphene oxide on mechanical properties is inspected during mechanical testing of sandwich panels and the results of (PS-GNPs) strain sensors will be compared with the strains produced during mechanical testing.

A review of FDM and graphene-based polymer composite

Graphene is a carbon that has a unique structure that is excellent in enhancing mechanical, electrical and thermal properties. The fused deposition modelling (FDM) process is a widely used 3D printing method for its low investment and operating cost. Although the FDM process is cheaper and affordable, yet the printed parts are more fragile compare to other 3D printing methods. This paper covers about FDM process and the type of base materials and filler materials. However, the focus is mainly on ABS and graphene. The mechanical properties of ABS/Graphene polymer composite and application of ABS and graphene in the industry were also discussed. Hence, it proved that graphene enhances the properties of ABS. This study is done to improve polymer-based filaments for future references.

ПОЛУЧЕНИЕ ГРАФЕНОВЫХ СТРУКТУР И НАНОПОЛИМЕРОВ С ИСПОЛЬЗОВАНИЕМ УЛЬТРАЗВУКОВЫХ КОЛЕБАНИЙ

Graphene-based polymer nanocomposites are considered a promising class of future materials. The degree of filling, the filler and binder nature, and the shape, size, and mutual arrangement of filler particles determine the properties of a polymer composite material. The destruction of nanoparticles aggregates occurs most effectively in liquid media under the action of ultrasonic vibrations. The authors proposed the technique and designed laboratory equipment for ultrasonic treatment of the finely-dispersed graphite suspension, carried out the ultrasonic treatment (UST) of finely-dispersed graphite powder. The suspensions based on graphite with a solvent were obtained. The authors carried out the experiments on producing graphene using the graphite liquid-phase exfoliation method at the ultrasonic treatment with different ultrasonic treatment times, analyzed experimental data, and selected the UST optimal time. The paper contains the results of the study of the effect of the graphite suspension base on the degree of ultrasonic liquid-phase exfoliation of graphite. The most effective synthesis of graphene structures using UST is synthesis from graphite suspensions based on dichloroethane, benzol, and dichlorobenzene. Graphene structures’ output ratio amounts to up to 66 %. The authors developed the technology for producing polymers modified with graphene structures using ultrasonic dispersion. Based on graphene synthesized by the graphite liquid-phase exfoliation, the authors obtained nanopolymers using ultrasonic vibrations, carried out DSC measurements, and studied their strength properties. The limit strength of elastic polymers is from 1.9 to 3.6 MPa at different concentrations of graphene inclusions. The residual elongation of samples within the deviation did not change and amounted to 200 %.

Layer by layer assembled functionalized graphene oxide-based polymer brushes for superlubricity on steel-steel tribocontact.

This study demonstrates a simple and multistep approach for a covalent functionalization of chemically-prepared graphene oxide (GO) using branched polyethylenimine (PEI) through nucleophilic addition reaction to prepare GO-PEI. Further layer-by-layer (LBL) assembly on functionalized GO-PEI with anionic polyelectrolyte, poly(acrylic acid sodium salt) (PAA) and poly(sodium 4-styrenesulfonate) (PSS) have been undertaken to fabricate polymer brushes (PB). The physicochemical structures of GO, GO-PEI and LBL assembled PB [GO-PEI-PAA and GO-PEI-PSS] have been explored using standard spectral and morphological analysis. The macrotribological results demonstrated that GO-PEI-PAA/GO-PEI-PSS (0.5 wt%) as paraffin oil dispersible additives significantly decreased the coefficient of friction (COF) and wear at different contact pressures of steel-steel tribopairs. The influence of contact pressure and load-bearing ability of the polymer-grafted GO as nanolubricants have been examined carefully. The COF of PB particles provided a reduction of 85% (low pressure, ∼0.9 MPa) and 66.65% (high pressure, ∼1.35 GPa) compared to lube paraffin oil and exhibited a lower specific wear rate (2.26 × 10-8 mm3 N-1 m-1) at macrotribological pin/ball-on-disc trials, revealing superior lubricity. The PB containing nanolubricants also exhibited high load-bearing ability (till ∼1000 N load, Pm ∼6.1 GPa) with considerably lower COF and wear, which were investigated using a four-ball tribotester. Among the functionalized polymeric GO particles, PSS polyelectrolyte containing GO-PEI-PSS showed better COF and wear reduction ability with extremely high load-bearing capacity due to the strong interfacial adhesion properties of PSS to generate strong protective synergetic lubricating tribofilm into the rubbing interfaces, which is comprehensively investigated by post-tribological analysis.

The Effect of Graphene Oxide Dispersion on Structure-Property Relationships in Graphene-Based Polymer Nanocomposites

The performance of graphene/polymer nanocomposites depends on many factors but the major factor is a nanoparticles dispersion and distribution into the host matrix. The present work investigates the effect of the dispersion of graphene oxide upon the structure-property relations in metallocene linear low density polyethylene (PE), homo polypropylene (PP), and blends thereof. These nanocomposites were prepared by solvent processing, where DMF and o-xylene were used as solvents for Graphene Oxide (GO) powder and the polymers respectively, before the two components were combined to form a well-mixed initial state. Characterization of the structure and crystallization of the nanocomposites was carried out by small- and wide-angle X-ray scattering and diffraction (SAXS and WAXD). The chemical structures were characterized by Fourier transform infrared spectroscopy (FTIR) and by Raman spectroscopy, and the latter used to calculate the ID/IG value for a pure GO samples. The thermal properties of the resulting nanocomposites were investigated by DSC and TGA in order to obtain Melting temperature ( ), crystallization temperature ( ) and degree of crystallinity ( ) as well as a range of degradation temperatures. The effect of GO on the mechanical properties was studied via the ultimate tensile strength and elastic modulus.

Conformations and thermal dynamics of graphene-based polymer nanocarpets

We model possible mechanical conformations and thermal dynamics of the recently synthesized graphene-based polymer nanocarpets for advanced optoelectronics applications, made by homogeneous valence attachment (functionalization) to one side of the graphene sheet of polyethylene chains or benzene rings. It is shown that on a flat substrate, the anisotropic quasi-two-dimensional nanocarpets always preserve a flat shape with the inner side bound to the substrate and with the attached polymer molecules at the outer side orthogonal to the plane of the graphene sheet. The flat shape of the nanocarpet bound to the substrate is resistant to thermal vibrations. The heat capacity of the nanocarpet increases monotonically with temperature in the equipartition limit. Most strong growth of heat capacity occurs for the graphene sheets with attached polyethylene chains at T⩾450 K, when the disordering of the lattice of the attached polymer chains starts to occur from the edges of the nanocarpet.

Microwave-assisted synthesis of conducting polymer matrix based thin film NaLa (MoO4)2-G-PPy composites for high-performance gas sensing.

Microwave-assisted quaternary nanocomposites containing NLM(NaLa (MoO4)2) semiconductors were combined with graphene-based polymers to activate gas sensing utilizing cyclic voltammetry. A cathode arranged for the scattering of graphene in NLM dependent on PPy conductive polymer is covered on a substrate with pre-assembled anodes, and concentrated to distinguish the location of CO2 and (CH3)2CO at room temperature (RT). Transmission electron microscopy, UV–visible spectroscopy, and Raman spectra affirm the closeness of few-layer graphene in the NLM-PPy polymeric nanocomposite and the current π–π collaboration between graphene and PPy. The NLM-graphene-PPy gas sensor demonstrates a high reaction and high selectivity for CO2 in a low focus scope of (25–1,000) ppm at RT. The acquired gas recognition exhibitions can be credited to the particular surface territory expanded by graphene, and to the improved collaboration between the film and the CO2 atoms through the π–electron arrangement. To examine the selectivity of the recognition of various gases dependent on graphene polymers, were made in (CH3)2CO, carbon dioxide (CO2) and air that explicitly express the perfect gas of compacted gas chambers in an unfilled vacuum chamber. The sensors offer direct electrical inspection. Finally, estimations have been presented that include various thicknesses of charge to represent the adsorption of CO2 and water molecules in graphene, and the alteration of the electronic structure of graphene achieved by the connection with the substrate and the particles.

Thermal and morphological study of graphene based polyurethane composites

Graphene-based polymer nanocomposites are highly used in the field of membranes, biomedical aids, automotive, electronics, actuators, aerospace and sensors. In this paper, the thermal and morphological study of polyurethane nanocomposites was carried out. Polyurethane nanocomposites were fabricated using the melt mixing in the presence of a solvent. Different weight percentages of graphene (2.5 wt%, 5 wt%, and 10 wt%) were incorporated for preparing the nanocomposites. The morphological study of the polyurethane and nanocomposites samples was explored by scanning electron microscope (SEM) to observe the dispersion of graphene nanomaterials in the polyurethane matrix. Fourier Transform Infrared Spectroscopy (FTIR) was applied to examine the chemical properties of the different polyurethane nanocomposite. The existence of graphene in the polyurethane matrix was studied using X-ray diffraction (XRD). The thermal analysis of the nanocomposite samples was analyzed using Thermogravimetric analysis (TGA). SEM showed that the graphene is dispersed throughout the polyurethane matrix. FTIR investigation showed that there is no change in the chemical properties of the polyurethane with the addition of graphene. XRD technique confirms the existence of graphene in the polyurethane matrix. TGA analysis concluded that the integration of graphene in the polyurethane matrix increases the thermal stability property of polyurethane. Therefore, as a result of the current study, polyurethane nanocomposites can be fabricated without any changes in chemical properties.

Anti-corrosion reinforcement of waterborne polyurethane coating with polymerized graphene oxide by the one-pot method

The research and preparation of excellent anti-corrosion coatings is still a difficult task and critical to practical applications. In this paper, phosphoric acid, dodecylbenzenesulfonic acid (DBSA), and polyaniline (PANI) were polymerized in-situ onto graphene oxide (GO) by the one-pot method to prepare dodecylbenzenesulfonic acid-PANI/phosphorylated graphene oxide (DPPGO). The results of TEM, FTIR, Raman spectrum, XRD, TGA, and XPS analysis showed that the DPPGO was successfully prepared. The SEM observations showed that DPPGO has best dispersibility and compatibility than GO and PANI/phosphorylated graphene oxide (PPGO) in waterborne polyurethane (WPU) matrix. To achieve anti-corrosion performance, a new type of graphene-based polymer nanocomposites water-based coating was developed and tested by electrochemical measurements. Through a series of electrochemical tests, it is concluded that the anti-corrosion performance of a composite coating DPPGO is significantly improved. The excellent anti-corrosion properties are due to the perfect dispersion and good compatibility of DPPGO in WPU.

Graphene/polyamide-6 microsphere composites with high electrical and mechanical performance

The development of innovative methods to prepare graphene-based polymer composites with remarkable properties has become a priority due to the many practical applications of these microstructures. Herein, a new technology was used to fabricate composites by combining graphene materials and polymer microspheres. Polyamide 6 (PA6) microspheres were synthesised by reaction-induced phase separation method, and they were wrapped with few-layer graphene (FLG) or graphene oxide (GO) by exfoliated adsorption method, which allows FLG and GO sheets to form a three-dimensional network structure in the PA6 matrix. Electrical and mechanical characterisation led to a distinct improvement in the properties of PA6 composites, which were superior to traditional graphene/polymer composites. Moreover, the process proposed in this work proved to be an effective method to prepare graphene/polymer composites, suitable for industrial production, and can be extended to other kinds of composites with nanofillers.

Micro-scale computational modeling of graphene-based nanocomposites – Influence of filler-matrix interface failure

The effect of failure at the filler-matrix interface on the tensile stress-strain response of graphene-based polymer nanocomposites is studied using micro-scale finite element (FE) modeling. Interfacial failure can occur in the form of debonding or slip. Based on previous studies (Jiang et al., 2014; Anagnostopoulos et al., 2015; Li et al., 2017), interfacial slip, which causes friction-like interaction between the filler and matrix, is identified as the major failure mechanism that affects the nanocomposite response. By establishing single-filler models in ABAQUS, it is demonstrated that interfacial slip affects the stress-strain response of the nanocomposite in two ways. Firstly, it limits the load that can be transferred to the filler. Secondly, it causes a shear displacement discontinuity across the interface, and this generates additional strain over and above those of the matrix and filler; this reduces the level of stress enhancement in the nanocomposite that the incorporation of fillers contribute, and under certain conditions, even weaken the nanocomposite. Models with fully aligned and randomly oriented fillers are also established to examine the influence of parameters such as filler orientation, interfacial slip strength, and filler aspect ratio, on the tensile response of the nanocomposite. The model developed is employed to describe the tensile response of an actual polyvinyl alcohol (PVA)- graphene oxide (GO) nanocomposite, and good correlation with experiments is observed.

Preparation and Characteristics of Graphene-based Polymeric Leather Fatliquor

Although the research of leather chemicals has experienced considerable advances, it remains imperative and challenging to develop functional ones; especially functionalized fatliquors or re-tanning agents. In consideration with the unique structure and properties, graphene oxide (GO) has been reported as a potential alternative to ameliorate the performance of leather. However, one of the intractable handicaps is how to make graphene penetrate evenly and react with collagen fibers. Here, we demonstrate a method for preparing graphene-based polymeric fatliquor (PFGO) via an amidation reaction between amino-groups of aminated graphene (AGO) and anhydride bonds of maleic anhydride-rapeseed oil copolymer (MRO), which was synthesized by free radical copolymerization. The results show that the as-prepared fatliquor has good emulsion stability and can penetrate into the collagen fibers uniformly. Compared with the control sample without graphene, the antibacterial, electromagnetic shielding, flame retardant and UV resistance characteristics of the PFGO-treated leather were significantly improved. Overall, this e?ective yet promising paradigm may provide an achievable solution toward developing graphene-based polymer composites simultaneously with high physical property and high functional performance.

Redox mechanisms of conversion of Cr(VI) to Cr(III) by graphene oxide-polymer composite

Alternative methods of aqueous chromium removal have been of great research interest in recent years as Cr (VI) is a highly toxic compound causing severe human health effects. To achieve better removal of Cr (VI), it is essential to understand the chemical reactions that lead to the successful removal of Cr species from the solution. Recent studies have demonstrated that graphene oxide (GO) based polymer beads cannot only adsorb Cr (VI) via electrostatic attractions but also reduce it to Cr (III), which is a much less toxic form of chromium. This conversion and the functional groups involved in this conversion, until now, were not elucidated. In the present study, we employed X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy to investigate the conversion pathway of Cr (VI) to Cr (III) in graphene-based polymer beads. The results showed that alcoholic groups are converted to carboxylic groups while reducing Cr (VI) to Cr (III). The inclusion of GO in the polymer beads dramatically increased the potential of Cr (VI) uptake and conversion to Cr (III), indicating polymers and nanomaterials containing alcohol groups can remove and convert chromium in water. Other functional groups present in the polymer bead play an important role in adsorption but are not involved in the conversion of Cr (VI) to Cr (III).

Concentration-Dominated Orientation of Phenyl Groups at the Polystyrene/Graphene Interface.

The interfacial orientation of aromatic groups plays a crucial role in determining the properties of graphene-based aromatic polymer nanocomposites. Here, the interfacial orientation of the polystyrene (PS) phenyl groups in contact with graphene is revealed by sum frequency generation (SFG) vibrational spectroscopy. The SFG spectra showed that the orientation of the phenyl groups is closely related to the interfacial concentration as the chains reach the quasi-equilibrium state. The phenyl groups remain in a relatively unrestricted state at a low concentration of the PS phenyl groups, and they prefer to recline to more favorably interact with graphene via a face-to-face configuration. Densely stacked phenyl groups are too crowded to form multilayer face-to-face interactions with graphene, and they prefer to remain upright, while π-π interactions are formed among the phenyl groups themselves in addition to the edge-to-face interactions to maximize the bonding energy of the π-π interactions. This is enthalpically favorable and driven mainly by the π-π interactions. This work provides important knowledge for the design and optimization of functional graphene-based aromatic polymer nanocomposites.

Novel designed quaternary CuZnSnSe semiconductor combined graphene-polymer (CuZnSnSe-G-PPy) composites for highly selective gas-sensing properties

We successfully synthesized quaternary nanocomposites containing CuZnSnSe semiconductors combined with graphene-based polymers for selective gas sensing and analyzed their cross-sensitivity using cyclic voltammetry. To investigate the selectivity of graphene-polymer-based detection of different gases was performed for Ammonia (NH3), oxygen (O2), carbon dioxide (CO2), into an emptied vacuum chamber. The sensors provide a direct accurate transformation into electrical signals in devices by recognizing CO2, O2, and NH3. It shows that the sensor has a high selectivity to CO2 by distinguishing with O2, NH3 in vapor-phase intelligently with accurate transformation into electrical signals in devices. Finally, the CuZnSnSe-G-PPy sensors demonstrate fast response/recovery times and a wide range of CO2, O2, NH3 detection. The superior sensing ability of mesoporous CuZnSnSe-G-PPy compared to CuZnSnSe-G and CuZnSnSe eventually is due to the implied optimum amount of synthesized sample. Finally, we proved a facile, low-cost route for the assembly of multiple gas-sensing devices with the potential for vast application.

Fabrication of polyamide 6 nanocomposites reinforced by the exfoliated graphene

ABSTRACT In this study, a green and efficient method was demonstrated to produce few-layer graphene (FLG) with high quality and yield via liquid-phase exfoliation (LPE) of graphite in sodium dodecyl benzenesulfonate aqueous solution by sonication. The final concentration of the as-prepared graphene was 0.96 mg mL−1 with a lateral size of about 2 μm after 2 h of sonication exfoliation. In addition, the polyamide 6/the exfoliated graphene (PA6/EG) nanocomposites were successfully fabricated by melt-blending injection. The effects of loading of EG on the mechanical properties of PA6 composites were systematically investigated. A noticeable enhancement was achieved on the PA6/EG nanocomposites. Compared with pure PA6, when the loading of EG is only 0.3 wt-%, the significant tensile strength and Young's modulus were increased by 26.7 and 21.1%, respectively, of PA6/EG composites. This green and easy process provides a choice for the application of high-performance graphene-based polymer composites.

Nonlinear \u201coddities\u201d at the percolation of 3D hierarchical graphene polymer nanocomposites

The nonlinear rheology of a novel 3D hierarchical graphene polymer nanocomposites was investigated in this study. Based on an isotactic polypropylene, the nanocomposites were prepared using simple melt mixing, which is an industrially relevant and scalable technique. The novel nanocomposites stand out as having an electrical percolation threshold (≈0.94 wt%) comparable to solution mixing graphene-based polymer nanocomposites. Their nonlinear flow behavior was investigated in oscillatory shear via Fourier-transform (FT) rheology and Chebyshev polynomial decomposition. It was shown that in addition to an increase in the magnitude of nonlinearities with filler concentration, the electrical percolation threshold corresponds to a unique nonlinear rheological signature. Thus, in dynamic strain sweep tests, the nonlinearities are dependent on the applied angular frequency, potentially detecting the emergence of a weakly connected network that is being disrupted by the flow. This is valid for both the third relative higher harmonic from Fourier-transform rheology, I3/1, as well as the third relative viscous, v3/1, Chebyshev coefficient. The angular frequency dependency comprised non-quadratic scaling in I3/1 with the applied strain amplitude and a sign change in v3/1. The development of the nonlinear signatures was monitored up to concentrations in the conductor region to reveal the influence of a more robust percolated network.

Toughening of graphene-based polymer nanocomposites via tuning chemical functionalization

Previous experiments on the mechanics of graphene-based polymer nanocomposites report their mechanical properties far below theoretical predictions. A critical factor in this regard is the nature and strength of nanofiller/matrix interfacial bonding. Herein, beneficial effects of chemical functionalization on the interfacial mechanical properties of graphene-based polymer nanocomposites are investigated using complementary experiments and molecular dynamics (MD) simulations. We report that by tuning the extent and chemistry of the functionalized species, (approximately 10%), graphene-PMMA nanocomposites can achieve superior mechanical properties by improving the interfacial load transfer. Compared to pure PMMA, an increase of 46% in Young's modulus and 119% in energy absorbed per unit volume during fracture, respectively, were achieved for 10% functionalized nanocomposites. Such an increase in energy absorbed was caused by a transition in crack propagation mechanism from interfacial slippage to crack arresting behavior, owing to the enhanced interfacial bonding. MD simulations revealed that such a change in mechanism is caused by the formation of both hydrogen bond networks and physical entanglements at the interface. While the methodology can be applied for different nanocomposite systems, the present results may provide an avenue for more efficient design of graphene-based nanocomposite structures.

Thermal properties of graphene-based polymer composite materials: A molecular dynamics study

Interfaces between graphene play a crucial yet poorly understood role in the transport of heat in graphene-based composite materials. The primary focus of this study was on developing a quantitative understanding of the mechanism underlying the heat flow through the structure of a graphene-based polymer matrix composite material. The macroscopic thermal properties of the composite material were studied to provide an effective way to improve thermal conductivity for polymers. Molecular dynamics simulations were performed to understand the thermal resistance of interfaces between graphene and to optimize the condition of the interface for nanoscale thermal reinforcement. A modified Maxwell Garnett effective medium theory was used to predict the thermal conductivity of the composite material. The results indicated that the thermal properties of a graphene-based polymer matrix composite material depends upon the details of the microscopic structure and atomic interactions within the composite material. Interfaces between graphene contribute significantly to the thermal conductivity of the composite material. This is even more critical for composite materials where the lateral size of graphene can affect the thermal performance of the composite material significantly. Low thermal boundary resistance and high thermal conductivity can be achieved by introducing the structure of a carbon cross-link network between graphene. The proper combination of graphene with large size and carbon cross-links with high density can lead to a fifty-fold improvement in overall thermal performance for the polymer matrix composite material. The relative position between graphene can be adjusted for the further optimization of interfacial conditions, but with little success in nanoscale thermal reinforcement. The bulk thermal conductivity of graphene nanoribbons has been found to be about 2570 W/m·K at room temperature. The results can provide a theoretical basis for understanding the applied physics of thermal transport at the nanoscale in graphene-based polymer matrix composite materials.