High thermal conductivity through simultaneously aligned polyethylene lamellae and graphene nanoplatelets (original) (raw)
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Nanomaterials, 2020
Thermal conductivity (k) of polymers is usually limited to low values of ~0.5 Wm−1K−1 in comparison to metals (>20 Wm−1K−1). (100)T3//(926)T4 The goal of this work is to enhance thermal conductivity (k) of polyethylene–graphene nanocomposites through simultaneous alignment of polyethylene (PE) lamellae and graphene nanoplatelets (GnP). Alignment is achieved through the application of strain. Measured values are compared with predictions from effective medium theory. A twin conical screw micro compounder is used to prepare polyethylene–graphene nanoplatelet (PE-GnP) composites. Enhancement in k value is studied for two different compositions with GnP content of 9 wt% and 13 wt% and for applied strains ranging from 0% to 300%. Aligned PE-GnP composites with 13 wt% GnP displays ~1000% enhancement in k at an applied strain of 300%, relative to k of pristine unstrained polymer. Laser Scanning Confocal Microscopy (LSCM) is used to quantitatively characterize the alignment of GnP flakes...
2022
To achieve high thermal conductivity (k) of polymer graphene nanocomposites, it is critically important to achieve efficient thermal coupling between graphene and its surrounding polymers through effective functionalization schemes. In this work, we demonstrate that edge-functionalization of graphene nanoplatelets (GnPs) can enable a larger enhancement of effective thermal conductivity in polymer-graphene nanocomposites, relative to basal plane functionalization. Effective thermal conductivity for edge case is predicted, through molecular dynamics simulations, to be up to 48% higher relative to basal plane bonding for 35 wt.% graphene loading with 10 layers thick nanoplatelets. This unique result opens up promising new avenues for achieving high thermal-conductivity polymer materials, which is of key importance for a wide range of thermal management technologies. The anisotropy of thermal transport in single layer graphene leads to very high in-plane thermal conductivity (~2000 W/mK...
Beilstein Journal of Nanotechnology
High-density polyethylene (HDPE)-based nanocomposites incorporating three different types of graphene nanoplatelets (GnPs) were fabricated to investigate the size effects of GnPs in terms of both lateral size and thickness on the morphological, thermal, electrical, and mechanical properties. The results show that the inclusion of GnPs enhance the thermal, electrical, and mechanical properties of HDPE-based nanocomposites regardless of GnP size. Nevertheless, the most significant enhancement of the thermal and electrical conductivities and the lowest electrical percolation threshold were achieved with GnPs of a larger lateral size. This could have been attributed to the fact that the GnPs of larger lateral size exhibited a better dispersion in HDPE and formed conductive pathways easily observable in scanning electron microscope (SEM) images. Our results show that the lateral size of GnPs was a more regulating factor for the above-mentioned nanocomposite properties compared to their t...
Polymer Composites, 2018
In-plane alignment of graphene nanoplatelets (GNPs) in thin thermal interface material layers suppresses the through-plane heat transport, which limits the performance of materials. In order to suppress the in-plane alignment of the GNP filler within polypropylene (PP) and increase the through-plane component, modification of GNP (MG) was performed in this study. For this aim, GNP was treated with diallyldimethylammonium chloride solution and filled with PP at different weight fractions by using a laboratory type high-speed thermo-kinetic mixer. The effect of MG loading into PP on thermal conductivity and surface resistivity of PP was measured. With using MG as a conductive filler for PP, instead of GNP, through-plane conductivity increased by 11%, however in-plane conductivity decreased by 33%. Modified GNP-filled PP showed better through-plane conductivity and surface resistivity than those of unmodified GNP-filled PP. Tensile and three point bending tests were performed to determine tensile and flexural properties of composites. Dynamic mechanical analysis was carried out to evaluate viscoelastic properties, such as storage modulus and loss modulus of composites. The thermal properties of samples were measured by using a differential scanning calorimetry, thermogravimetric analysis, and thermo-mechanical analysis. Scanning electron microscopy was utilized to observe the fracture surfaces of the composites after tensile tests. POLYM.
Enhanced thermal conductivity of graphene nanoplatelets epoxy composites
Materials Science-Poland
Efficient heat dissipation from modern electronic devices is a key issue for their proper performance. An important role in the assembly of electronic devices is played by polymers, due to their simple application and easiness of processing. The thermal conductivity of pure polymers is relatively low and addition of thermally conductive particles into polymer matrix is the method to enhance the overall thermal conductivity of the composite. The aim of the presented work is to examine a possibility of increasing the thermal conductivity of the filled epoxy resin systems, applicable for electrical insulation, by the use of composites filled with graphene nanoplatelets. It is remarkable that the addition of only 4 wt.% of graphene could lead to 132 % increase in thermal conductivity. In this study, several new aspects of graphene composites such as sedimentation effects or temperature dependence of thermal conductivity have been presented. The thermal conductivity results were also com...
Development of low density polyethylene/graphene nanoplatelets with enhanced thermal properties
2018 IEEE 9th International Conference on Mechanical and Intelligent Manufacturing Technologies (ICMIMT), 2018
The polymer technologies have evolved due to the vast applications of polymer nanocomposites with improved properties such as mechanical and thermal stability to replace the conventional materials. The aim of this study is to develop low density polyethylene (LDPE) / graphene nanoplatelets (GNP) with enhanced thermal properties. Different loadings of GNP (0, 0.5, 1.0 and 1.5 wt%) were incorporated into the LDPE through melt mixing technique using a twin-screw extruder with the screw speed at 50 rpm to produce LDPE/GNP polymer nanocomposites. The degradation behavior of LDPE/GNP was characterized by thermogravimetric analysis (TGA), while the melting temperature (Tm), recrystallization temperature (Tc) and crystallinity (Xc) of polymer composite were analyzed by differential scanning calorimeter (DSC). The results exhibited that Tc decreased by the incorporation of GNP as compared to the pure LDPE. Degree of crystallinity of LDPE/GNP composites was observed to be lower than the pure ...
Thermally Conductive Graphene-Polymer Composites: Size, Percolation, and Synergy Effects
The rapidly increasing device densities in electronics dictate the need for efficient thermal management. If successfully exploited, graphene, which possesses extraordinary thermal properties, can be commercially utilized in polymer composites with ultrahigh thermal conductivity (TC). The total potential of graphene to enhance TC, however, is restricted by the large interfacial thermal resistance between the polymer mediated graphene boundaries. We report a facile and scalable dispersion of commercially available graphene nanoplatelets (GnPs) in a polymer matrix, which formed composite with an ultrahigh TC of 12.4 W/m K (vs 0.2 W/m K for neat polymer). This ultrahigh TC was achieved by applying high compression forces during the dispersion that resulted in the closure of gaps between adjacent GnPs with large lateral dimensions and low defect densities. We also found strong evidence for the existence of a thermal percolation threshold. Finally, the addition of electrically insulating boron-nitride nanoparticles to the thermally conductive GnP-polymer composite significantly reduces its electrical conductivity (to avoid short circuit) and synergistically increases the TC. The efficient dispersion of commercially available GnPs in polymer matrix provides the ideal framework for substantial progress toward the large-scale production and commercialization of GnP-based thermally conductive composites.
International Journal of Plastics Technology, 2018
The logical outline and assembly of structural-functional materials are a progressive tendency of materials knowledge. The high specific surface areas and superior properties of graphene (Gr) spread in low-density polyethylene (LDPE) considerably improved the thermal stability and conductivity of LDPE/Gr composites. The electrical conductivity upgraded owing to the great thermal strength of Grs in LDPE matrix. Outstanding distribution of Grs was accomplished. LDPE/Gr composites were characterized by scanning electron microscopy, transmission electron microscope, Raman spectra, X-ray diffraction, thermogravimetric analyses and differential scanning calorimeter for studying the distribution, morphology and thermal strength of Gr composites. Results display that the presence of filler does not create an alteration in the microscopic structure of polymers. However, on a macroscopic scale, addition of Gr improved significantly the thermal and electrical properties of all LDPE/Gr compounds.
Based on the fast growth of the device performance, there has been an increasing demand for handling the issue of thermal management in electronic equipments. Therefore, it is of great significance to improve the thermal conductivity of thermoplastics, which are commonly used in electronic components. However, the difficulty of graphene dispersion and strong interfacial phonon scattering restrict the heat dissipation performance of graphene/thermoplastic composites, especially in the case of polypropylene (PP) or polyethylene (PE). Here, we propose a single-step and versatile approach to fabricate graphene/ thermoplastic composites with a remarkable thermal conductivity enhancement. The composites were prepared by coating graphene on polymer powder first, followed by hot pressing. As a result, an interconnected graphene framework can be developed in the thermoplastic matrix, leading to significant heat transfer enhancement of the composites. At a 10 wt% graphene content, the thermal conductivity reaches 1.84, 1.53, 1.43, and 1.47 W m À1 K À1 for PE, PP, PVA (poly(vinyl alcohol)), and PVDF (poly(vinylidene fluoride)) composites, respectively. Our finding provides a path to develop a variety of highly thermally conductive thermoplastic composites for use in heat dissipation and other thermal applications.