Graphene Nanoplatelets Loading Research Articles

Innovative dispersion techniques of graphene nanoplatelets (GNPs) through mechanical stirring and ultrasonication: Impact on morphological, mechanical, and thermal properties of epoxy nanocomposites

Graphene nanoplatelets (GNPs) have attracted tremendous interest due to their unique properties and bonding capabilities. This study focuses on the effect of GNP dispersion on the mechanical, thermal, and morphological behavior of GNP/epoxy nanocomposites. This study aims to understand how the dispersion of GNPs affects the properties of epoxy nanocomposite and to identify the best dispersion approach for improving mechanical performance. A solvent mixing technique that includes mechanical stirring and ultrasonication was used for producing the nanocomposites. Fourier transform infrared spectroscopy was used to investigate the interaction between GNPs and the epoxy matrix. The measurements of density and moisture content were used to confirm that GNPs were successfully incorporated into the nanocomposite. The findings showed that GNPs are successfully dispersed in the epoxy matrix by combining mechanical stirring and ultrasonication in a single step, producing well-dispersed nanocomposites with improved mechanical properties. Particularly, the nanocomposites at a low GNP loading of 0.1 wt%, demonstrate superior mechanical strength, as shown by increased tensile properties, including improved Young's modulus (1.86 GPa), strength (57.31 MPa), and elongation at break (4.98). The nanocomposite with 0.25 wt% GNP loading performs better, according to the viscoelastic analysis and flexural properties (113.18 MPa). Except for the nanocomposite with a 0.5 wt% GNP loading, which has a higher thermal breakdown temperature, the thermal characteristics do not significantly alter. The effective dispersion of GNPs in the epoxy matrix and low agglomeration is confirmed by the morphological characterization. The findings help with filler selection and identifying the best dispersion approach, which improves mechanical performance. The effective integration of GNPs and their interaction with the epoxy matrix provides the doorway for additional investigation and the development of sophisticated nanocomposites. In fields like aerospace, automotive, and electronics where higher mechanical performance and functionality are required, GNPs' improved mechanical properties and successful dispersion present exciting potential.

Graphene-loaded recycled PET: Exploring and enhancing electrical conductivity through processing and laser treatments near the electrical percolation threshold

The blend of polyethylene terephthalate (PET), among the most employed polymer, with graphene, among the most adopted conductive carbon materials, may represent a favorable and sustainable approach for the fabrication of added-value conductive composite materials. This work targeted on the fabrication of melt-compounded composites via injection molding process starting from homemade recycled PET and different loadings of graphene nanoplatelets (GnPs) with different lateral sizes (5 and 25 μm, respectively), used as conductive fillers. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and SEM investigation of the different r-PET/GnP-based compounds provided information about composition, textural and structural properties of the melt-compounded specimens, which were correlated with their DC electrical properties. Graphene loadings higher than ca. 9.5–10 wt% were found enough to achieve the electrical percolation within the two material types. With higher graphene loadings, electrical conductivity increased, due to the formation of a progressively developed percolation network. Notably, the effects of the different GnP loadings, GnP lateral sizes and crystallinity degree of the polymer on the conductivity of the of the melt-compounded specimens were investigated. Furthermore, the effect on the electrical properties of CO2 laser irradiation at different scribing speeds on r-PET/GnP composites with graphene loading below the percolation threshold, was verified. By altering locally the morphology and structure, the irradiation process impacted the electrical properties. Notably, the resulting low sheet resistance suggests potential applications in low-power electronics. In brief, the approach and methodology adopted in the present work, along with the results, can contribute to the development of future upcycling into more valuable and sustainable conductive materials and devices based on recycled PET with a reduced environmental footprint.

Ultrasonication Influence on the Morphological Characteristics of Graphene Nanoplatelet Nanocomposites and Their Electrical and Electromagnetic Interference Shielding Behavior.

Graphene nanoplatelets (GNPs)/epoxy composites have been fabricated via gravity molding. The electrical and thermal properties of the composites have been studied with variable GNP type (C300, C500, and C750, whose surface areas are ~300, 500, and 750 m2/g, respectively), GNP loading (5, 10, 12, and 15 wt.%), and dispersion time via ultrasonication (0, 30, 60, and 120 min). By increasing the time of sonication of the GNP into the epoxy matrix, the electrical conductivity decreases, which is an effect of GNP fragmentation. The best results were observed with 10-12% loading and a higher surface area (C750), as they provide higher electrical conductivity, thereby preserving thermal conductivity. The influence of sonication over electrical conductivity was further analyzed via the study of the composite morphology by means of Raman spectroscopy and X-ray diffraction (XRD), providing information about the aspect ratio of GNPs. Moreover, electromagnetic shielding (EMI) has been studied up to 4 GHz. Composites with C750 and 120 min ultrasonication show the best performance in EMI shielding, influenced by their higher electrical conductivity.

Wear‐resistant layers containing graphene derivatives

AbstractThe effect of carbon filler wt% ratios on the microstructural and tribological properties of the ultra‐high molecular weight polyethylene (PE)/graphene nanoplatelets (GNP), PE/graphene oxide (GO), and PE/carbon nanotube (CNT) composites and PE/GNP‐GO hybrid composite layers was studied to determine the best tribological performance after the dry wear test. The layers had a semi‐crystalline structure like PE, but the shifts in the peaks showed the presence of interactions between the fillers and PE matrix, according to x‐ray diffraction (XRD) analysis. FTIR analysis results indicated that GO‐containing layers caused interactions and new bonds. The lowest values for the friction coefficient were found in layers containing GNP and GO, which had a lubricating effect. The friction coefficient decreased by 83.24% in the PE/0.7GO composite layer compared to PE. Wear resistance of the PE/3GNP and PE/1GO layers were the highest compared to PE and other layers. The PE/3GNP and PE/1GO layers improved the wear resistance of PE by 12% and 11%, respectively. Abrasive wear and fatigue wear tracks on the worn surface of the PE/3GNP and PE/1GO composite layer were significantly reduced compared to PE and other layers. This study suggests that layers that will provide the highest molecular interaction with PE and improve its wear resistance will be produced with GO and nano‐sized GNP.Highlights The interaction of graphene‐derived fillers with PE and its effect on friction and wear properties were investigated. GNP and GO are the best filler materials among the graphene derivatives for increasing wear resistance. High wear resistant of layers achieved at 3 wt% GNP loadings. Layers containing GO had the lowest friction coefficient values among the other layers.

Synthesis, characterization, thermal and mechanical behavior of polypropylene hybrid composites embedded with CaCO<sub>3</sub> and graphene nano-platelets (GNPs) for structural applications

<abstract> <p>In this study, ultra-fine graphene nanoplatelets (GNPs) were employed as nanofillers to reinforce a polypropylene (PP) matrix. This was done in conjunction with a polypropylene grafted maleic anhydride (PP-MAH) compatibilizer and calcium carbonate (CaCO<sub>3</sub>), with the aim of improving the mechanical and thermal properties of the resulting hybrid composites. Formulations for the hybrid composites were fabricated by compounding the PP matrix with varying weight percentages of GNPs (x = 0.5, 1.0, 1.5, 2.0), 2 wt.% CaCO<sub>3</sub>, and 5 wt.% PP-MAH using a twin-screw extruder followed by injection molding. This research thoroughly investigates the mechanical and thermal characteristics. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR) results confirm the successful development of hybrid composites. The thermal stability, crystallization temperature, melting temperature, tensile strength, flexural strength, and impact resistance were evaluated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), universal testing machine, and low-velocity impact tester, respectively. The results indicated a significant improvement in the tensile strength of the PP matrix with the addition of GNPs, with the highest enhancement observed at 1.5 wt.% GNP loading, where the tensile strength reached a maximum of 40.54 MPa. This improvement was attributed to the proper interconnection, bonding, and compounding of PP with GNPs, thus leading to an increase in the load transfer efficiency.</p> </abstract>

Synergistic improvement of mechanical, electrical and thermal properties by graphene nanoplatelets in polyaniline incorporated rubbery thermoplastic composites

Here, thermoplastic natural rubber (TPNR) blend filled with polyaniline (PANi) and graphene nanoplatelets (GNPs) was fabricated via melt blending and compression moulding. The synergistic influence of including 1–5 wt% GNPs with 3 wt% PANi in nanocomposites on the mechanical via tensile test, Impedance electrical test, thermal stability via thermogravimetric analysis test and morphologic observation were examined. Inclusion of 2 wt% of GNPs increased by 62.8 % on tensile strength and 151.8 % on Young's modulus of TPNR/PANi. The highest electrical conductivity and thermal stability were achieved in the same nanocomposite composition. With a low loading of GNPs, an electrical conductivity of 2.6 E−9 S/cm was achieved which potential to be a new semi-conductive material. At this optimum content, the scanning electron microscopy micrograph revealed a homogenous distribution of GNPs in the TPNR/PANi blend as well as good matrix-filler interaction. To be practical in real application, cost-effectiveness is another important aspect to be determined. In this work, researchers evaluated the cost-performance of each system (TPNR, TPNR/PANi and TPNR/PANi/GNP) based on material costs, mechanical and electrical properties. Different general trends (positive, negative and synergistic) of cost-efficiency relationship were obtained for different material system and the priority greatly depends on their intended uses.

In-situ monitoring of crack growth and fracture behavior in composite laminates using embedded sensors of rGO coated fabrics and GnP paper

Graphene-based nanomaterials have found significant interest in the development of embedded sensors to monitor the fracture behavior in composite structures. In this work, in-situ crack propagation and fracture behavior within a glass fiber reinforced polymer composite (GFRP) was monitored using embedded reduced graphene oxide (rGO) coated fabrics and highly conductive graphene nanoplatelet (GnP) paper. All laminates were fabricated using the resin infusion process. The piezoresistive performance of both types of laminates was evaluated using in-plane and out-of-plane mechanical tests. The effect of GnP paper thickness (50/150/240 µm) and loading rate was also evaluated using tensile and Mode-I fracture loadings. Piezoresistivity of the sensors was reduced by increasing loading rate during tensile tests. All laminates with GnP paper exhibited poor mechanical performance under tensile loading. The laminates with 50 µm GnP paper showed highest sensitivity under Mode-I loading. In comparison to pristine laminates, the interlaminar fracture toughness of laminates with 50 µm GnP paper was reduced by 70%. Furthermore, laminates with rGO coated fabrics demonstrated stable crack propagation under Mode-I loading as compared to GnP based laminates. The fractured surfaces were analyzed using scanning electron microscopy to investigate the underlying fracture mechanisms of the sensors in the composite laminates.

Thermal, mechanical, thermo‐mechanical and morphological properties of graphene nanoplatelets reinforced green epoxy nanocomposites

AbstractThe efficient inclusion of GNPs (graphene nanoplatelets) as an effective nano‐fillers for green polymer matrices produced with 28% of carbon originating from biomass tends to significantly improve mechanical and thermal properties. In the present work, green epoxy nanocomposites with low loading of (0.1, 0.25, and 0.5) wt% of the GNPs were made using a solution blending technique using acetone as the solvent. In mechanical stirring, the ultrasonic bath was used to ensure the efficient dispersion of GNPs within green epoxy. The resulting nanocomposites were comprehensively characterized and compared to unfilled green epoxy. Different tools were used to appraise morphological, thermal, thermo‐mechanical, and mechanical behavior. The results confirmed through FE‐SEM showed an optimal dispersion of GNPs with nanocomposites. The thermal degradation temperature (Td) of GNPs curve with 0.25 wt% loading was shifted toward higher temperature (from 336°C to 342°C) due to low percentage of loading of GNPs which showed an enhance thermal stability of polymer matrix with 0.25 wt% loading. The mechanical results were also in lined with previously published literature, in the tensile test 6.45% and hardness 13.3% increment was achieved. Overall, the results underscored significant improvements in green nanocomposite performance with low wt% of GNPs.Highlights The study focuses on development and characterization of green epoxy nanocomposites, which utilize environmentally friendly materials as a matrix, highlighting the significance of sustainability. The study explores effects of low loading of GNPs in green epoxy nanocomposites. The results demonstrate significant improvements in mechanical and thermal properties with optimized presence of GNPs. This investigation provides insights into optimal amount of GNPs required to achieve improved properties. Research evaluates multifaceted analysis provides a holistic understanding of performance enhancements achieved through inclusion of GNPs.

Study of thermal and mechanical behavior by analyzing reinforcement effect of graphene nanoplatelets on polyamide-66 composite system developed via melt-mixing technique

In the present study, graphene nanoplatelets (GNP) reinforced polyamide 6,6 (PA-66) composite was studied to investigate the thermal and mechanical properties of PA-66/GNP composite. The composites were developed by varying wt% (1, 3, 5, and 10 wt%) of GNP loading using a co-rotating, intermeshing, twin-screw extruder via melt-mixing and injection molding process. In order to understand the thermal and mechanical behavior of PA-66/GNP composite, various thermal (TGA and DSC) and mechanical (tensile, impact, and flexural) tests were carried out. The FTIR spectral analysis was done to identify the presence of different functional groups in the PA-66/GNP composite, indicating the strong enough Vander-Waals interaction between the PA-66 matrix and GNP filler contents. The TGA result shows a significant enhancement in the thermal stability of the composite by increasing wt% of GNP. The DSC analysis exhibits a significant reduction in enthalpy of fusion (∆Hm) and a decrease in the degree of crystallinity with increasing wt% of GNP, reflecting a depressed form of α-crystalline structure. Further, the significant growth in tensile modulus and tensile strength were identified under the mechanical performance of the PA-66/GNP composite. An increasing trend in tensile modulus and tensile strength characteristics was observed, and tensile modulus exhibited an enhancement of ∼96% than pure PA-66 at 10 wt% of GNP. Also, the tensile strength is found to be ∼16% higher than that of pure PA-66 matrix. Similarly, the impact test result shows a decreasing trend in impact strength on increasing wt% of GNP reinforcements, indicating the restriction to the molecular mobility due to improved brittle behavior. Further, the flexural modulus is found to be increased by ∼28% at 10 wt%, and the flexural strength is found to have an enhancement of ∼9% at 3 wt% than pure PA-66 polymer matrix of GNP loadings, respectively. The influence of GNP filler content reinforced PA-66 composite on the thermal and mechanical properties is found to be noteworthy.

Studying the relationship between microstructure and properties of polylactic acid/styrene-ethylene butyl-styrene blend reinforced by graphene

The main purpose of this study was to investigate the relationship between microstructure and mechanical performance of polylactic acid when mixed with styrene-ethylene butylene-styrene copolymer and also graphene nanoplatelets. For this purpose, a series of neat polymer blends were first prepared with varying mixing ratios through a one-step melt mixing technique. Subsequently, the effect of various loadings of graphene nanoplatelets on the best mixing ratio (optimal composition) of the binary blend was investigated. To understand the different performances of various nanocomposites, the correlation of mechanical, rheological, and microstructural properties was thoroughly investigated using X-ray diffraction, scanning electron microscopy, linear viscoelastic behavior, tensile testing, and impact strength analyses. Furthermore, the influence of the mixing sequence of nanocomposites preparation on the microstructure and mechanical performance of nanocomposites was studied. Results demonstrated that the incorporation of graphene nanoplatelets as well as mixing sequence has a substantial effect on the final properties of prepared nanocomposites which was deeply discussed.

Improved rheological, barrier, antibacterial, and electromagnetic interference shielding properties of graphene and graphene derivatives based linear low density polyethylene nanocomposites

AbstractMultifunctional polymer/graphene based lightweight and flexible nanocomposite films are increasingly being utilized in the packaging, electronics, and pharmaceutical industries together. Herein, two graphene derivatives: silver nanoparticle decorated reduced graphene oxide (G‐Ag) and chemically reduced graphene oxide (rGO) prepared by wet chemical method and graphene nanoplatelets (GNP) have been incorporated into linear low density polyethylene (LLDPE) thermoplastic matrix via melt compounding method. The incorporation of graphene derivatives affected the physico‐mechanical, electrical and thermal conductivity, and barrier properties (both oxygen and water vapor permeability) of the nanocomposite films. With 5 wt% of G‐Ag, rGO, and GNP loading, the thermal conductivity of these three nanocomposite films was enhanced by an average of 136.7%, 123%, and 143.3%, respectively. Graphene having high specific surface area and aspect ratio allow for a tortuous passage of oxygen and water molecules through the nanocomposite film, ultimately improving both oxygen and water vapor impermeability qualities for all LG‐Ag, LrGO, and LGNP nanocomposites. Moreover, the films have been tested against both gram‐positive and gram‐negative bacteria to ensure their bactericidal activity. The prepared composite films also showed Electromagnetic Interference (EMI) shielding effectiveness (−21, −17, and −19 dB) higher than the commercial cut‐offs. The thermoplastic nanocomposite films with promising thermal conductivity might be an excellent choice for bacteria‐resistant and barrier‐capable packaging and efficient thermal management EMI shields in electronics.

Heterogeneous Nucleation of High-Density Polyethylene Crystals on Graphene within Microdomains

In polymer processes, nucleating agents are often used to control the kinetics of crystallization, but their application remains largely a matter of trial and error. Thermodynamically, the efficiency of a nucleating agent can be quantified by the difference in substrate/crystal, crystal/melt, and substrate/melt interfacial energies, Δσ. In this work, the efficiency of graphene nanoplatelets (GNP) as nucleating agents for high-density polyethylene (HDPE) is investigated. HDPE nucleates and crystallizes rapidly, so Δσ can be especially difficult to measure experimentally. To overcome this difficulty, blends of HDPE+GNP are confined to microdomains so that crystallization becomes nucleation limited. Two methods of microdomain formation are employed. In the first, HDPE+GNP is melt-blended with an immiscible matrix of polystyrene (PS), and crystallization is characterized using differential scanning calorimetry (DSC); in the second, dispersions of HDPE+GNP in toluene are sprayed onto PS substrates, and crystallization is characterized with polarized optical microscopy (POM). Heterogeneous nucleation rates at several crystallization temperatures and for several GNP loadings were measured by these two methods and found to give excellent agreement across GNP loadings. The value of Δσ for HDPE+GNP is calculated to be 0.83 ± 0.18 erg/cm2. This value is only 2.8 times larger than that reported for HDPE nucleated heterogeneously on a HDPE fiber, a nearly ideal nucleating agent for HDPE, and much smaller than many of the best nucleating agents reported for other polymers. We conclude that GNP is an efficient nucleating agent for HDPE.

Synergistic effects of zinc borate and graphene on enhanced thermal stability and antimicrobial properties of poly(methyl methacrylate)

AbstractThe use of graphene nanoplatelets (GnP) as reinforcing material for thermoplastic polymer matrices, polymethyl methacrylate (PMMA) and zinc borate (ZnB), as an antimicrobial and fire‐retardant agent was studied. PMMA‐ZnB and PMMA‐GnP‐ZnB (ZG) composite films were fabricated with different ZnB concentrations (2.5, 5, 10 wt%) by solvent casting method using acetone. The effect of additives on the antimicrobial activity, thermal and mechanical properties, and surface morphologies of the composites were investigated. Antimicrobial surface activity tests were conducted against seven microorganisms, including bacterial and fungal species. An improvement in antimicrobial activity by up to 99.99% with increasing ZnB content was observed. Thermal stability was increased with increasing concentration of ZnB and a combination of ZnB and GnP additions. 10% ZG‐based composites increased the % char residue value of PMMA from 0.5% to 9.3%. The incorporation of the ZnB and GnP into the PMMA matrix resulted in an increase in the calculated limiting oxygen index (LOI). 10% and 50% weight loss temperature increased by 11.7°C and 3.7°C, respectively, for 10% ZG composites. The Young's modulus of the composites increased with increasing ZnB and a combination of ZnB and GnP loading (increasing by 16% to 2033 MPa with the addition of 10 wt% ZG). The commercial application for this study would be in high touch and piano black automotive interior, construction, and medical applications.

Biocompatibility of Poly-Lactic Acid/Nanohydroxyapatite/Graphene Nanocomposites for Load Bearing Bone Implants

In this study, poly-lactic acid (PLA), nanohydroxyapatite (NHA), and graphene nanoplatelets (GNP) were blended to develop a nanocomposite material suitable for load-bearing bone implants with the potential for strain-sensing applications. The tensile properties and impact strength of the PLA-NHA nanocomposite were analyzed, as these are crucial biomechanical properties for load-bearing and strain-sensing applications. It was found that the impact strength decreased by 7.9% (0.05 wt% GNP) and 25.7% (0.1 wt% GNP) with increasing GNP loading compared to 0.01 wt% GNP. Besides, the biocompatibility of nanocomposites (PLA-NHA, PLA-mNHA, and PLA-mNHA-GNP) was evaluated through in-vitro analysis by attaching MG63 cells to the nanocomposites and observing their proliferation and differentiation over 7 and 21 days of incubation. The biocompatibility of the prepared nanocomposites was determined based on their ability to attach with MG63 cells, thus allowing the cells to proliferate and enhance their ability to differentiate. Results showed that the PLA-5wt%NHA nanocomposite provided better cell spreading compared to pure PLA, while the PLA-5wt%mNHA nanocomposite had the highest rate of cell proliferation. The biocompatibility of the nanocomposites was further confirmed by field emission scanning electron microscope (FESEM) imaging, MTT assays, and alkaline phosphatase (ALP) assays.

Incorporating Graphene Nanoplatelets and Carbon Nanotubes in Biobased Poly(ethylene 2,5-furandicarboxylate): Fillers' Effect on the Matrix's Structure and Lifetime.

Poly(ethylene 2,5-furandicarboxylate) (PEF) nanocomposites reinforced with Graphene nanoplatelets (GNPs) and Carbon nanotubes (CNTs) were in situ synthesized in this work. PEF is a biobased polyester with physical properties and is the sustainable counterpart of Polyethylene Terephthalate (PET). Its low crystallizability affects the processing of the material, limiting its use to packaging, films, and textile applications. The crystallization promotion and the reinforcement of PEF can lead to broadening its potential applications. Therefore, PEF nanocomposites reinforced with various loadings of GNPs, CNTs, and hybrids containing both fillers were prepared, and the effect of each filler on their structural characteristics was investigated by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), and X-Ray Photoelectron Spectroscopy (XPS). The morphology and structural properties of a hybrid PEF nanocomposite were evaluated by Transmission Electron Microscopy (TEM). The thermo-oxidative degradation, as well as lifetime predictions of PEF nanocomposites, in an ambient atmosphere, were studied using Thermogravimetric Analysis (TGA). Results showed that the fillers' incorporation in the PEF matrix induced changes in the lamellar thickness and increased crystallinity up to 27%. TEM analysis indicated the formation of large CNTs aggregates in the case of the hybrid PEF nanocomposite as a result of the ultrasonication process. Finally, the presence of CNTs caused the retardation of PEF's carbonization process. This led to a slightly longer lifetime under isothermal conditions at higher temperatures, while at ambient temperature the PEF nanocomposites' lifetime is shorter, compared to neat PEF.

Dielectric and electromagnetic interference shielding properties of nano‐silicon carbide/montmorillonite and graphene nanoplatelets filled polyvinylidene fluoride/poly(3,4‐ethylenedioxythiophene)‐block‐poly(ethylene glycol) blend nanocomposites

AbstractHerein, hybrid polymer nanocomposite films comprising polyvinylidene fluoride (PVDF) and poly(3,4‐ethylenedioxythiophene)‐block‐poly(ethylene glycol) (PEDOT‐block‐PEG) as matrices and silicon carbide nanoparticles (SiC NPs), montmorillonite (MMT) nanoclay, and graphene nanoplatelets (GNPs) as nanofillers were fabricated by solution casting. The structural, morphological, and thermal characteristics of the nanocomposite films were assessed using Fourier transform infrared spectroscopy (FTIR), x‐ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric analyzer (TGA), and differential scanning calorimetry (DSC). The SEM results show the homogeneous distribution of nanofillers within the polymer matrix. The dielectric behavior and electromagnetic interference shielding efficiency (EMI SE) of the nanocomposites were also analyzed. The maximum dielectric constant (ε) and dielectric loss (tan δ) obtained are 47.77 and 12.08, respectively, at lower frequency (50 Hz, 150°C). The maximum EMI SE was observed to be 16.8 dB in the Ku‐band region (12–18 GHz) for the nanocomposites with 20 wt% SiC, 8 wt% MMT, and 2 wt% GNPs loading. The EMI shielding was found to be absorption dominant and originated from the formation of a conductive network between hybrid nanofillers within the PVDF/PEDOT‐block‐PEG blend thereby improving the EMI SE values. These results suggest that PVDF/PEDOT‐block‐PEG/SiC/MMT/GNPs nanocomposites can be used as an efficient EMI shielding material.

Thermal Properties of Graphene Nanoplatelets Reinforced Crosslinked and Short Chain Branched Polyethylenes for Geothermal Pipe Applications

AbstractTwo types of polyethylenes, the crosslinked high‐density polyethylene (PEX) and the short‐chain branched medium‐density polyethylene (polyethylene of raised temperature resistance [PE‐RT]), are selected as matrices for graphene nanoplatelets (GNPs) nanocomposites preparation (PEX/GNPs, PE‐RT/GNPs). The melt‐mixing technique is used to synthesize the nanocomposites containing various loadings of GNPs. Differential scanning calorimetry (DSC) is employed to study the effect of the GNPs on the melting and crystallization behavior of the prepared materials. The thermal stability of the nanocomposites was evaluated by thermogravimetric analysis (TGA). Laser flash analysis (LFA) is used to estimate the thermal conductivity of both PEX and PE‐RT/GNPs nanocomposites. TGA measurements reveal that PEX nanocomposites present decreased thermal stability with increasing filler content. The DSC results show that the crystallinity of both matrices increases with increasing filler content. PEX/GNPs nanocomposites show more significant thermal conductivity augmentation compared to the corresponding PE‐RT nanocomposites.

Mechanical and thermal properties of graphene nanoplatelets-reinforced recycled polycarbonate composites

Nanocomposites have received significant interest in recent years, as they offer improved properties compared to conventional materials for various applications. Among many available nanofillers, graphene nanoplatelets (GNP) have shown promising results for polymer-based nanocomposite applications. This paper investigates the mechanical and thermal properties of GNP-reinforced virgin and recycled polycarbonate (PC) nanocomposites blended via a twin-screw extruder. Effects of various key processing parameters such as filler concentration, processing speed, barrel/die set temperature, and PC type (virgin and recycled) on the reinforced composites were examined. Mechanical properties were characterised by tensile testing, while thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to characterise the thermal properties. The results show that the processing speed and barrel/die set temperature have a slight influence, while the filler concentration significantly affects the properties of PC/GNPs composites. The Young's modulus and yield strength were enhanced with increasing GNP loading, where the maximum enhancement of Young's modulus was obtained as ∼33% for virgin-PC/GNP and ∼39.5% for recycled-PC/GNP composites at 10 wt.-% GNP loading. However, the failure strain was reduced with the increased GNP loading for both virgin and recycled PC/GNP composites. Embedding GNP into the PC matrix only slightly influenced the thermal stability and glassy transition temperature (Tg). The highest thermal stability for virgin PC/GNP composites was observed with 1 wt.-% (2.74% increase with respect to virgin PC), while for recycled PC/GNP, it was observed with 10 wt.-% (2.42% increase with respect to recycled PC) GNP loading. Under the same GNP loading, recycled PC-based composites showed lower thermal stability than virgin PC-based composites. The Tg evaluated from DSC showed a rise under 1 wt.-% GNP for virgin PC/GNP and decrease afterwards with higher filler loading, while an irregular variation for recycled PC/GNP was observed.

A study on graphene reinforced carbon fiber epoxy composites: Investigation of electrical, flexural, and dynamic mechanical properties

AbstractIn this study, graphene nanoplatelets (GNPs) added to epoxy matrix composite reinforced by aeronautical grade carbon fibers (CFs) were fabricated by the vacuum infusion method, and the effect of different GNPs contents (0.05, 0.25, and 1.25 wt%) on electrical conductivity, flexural properties, and dynamic mechanical properties were investigated. The results revealed an 8‐ and 73‐times improvement in conductivity values across the thickness with the addition of 0.05 and 0.25 wt% GNPs, respectively, compared to the neat composite. Flexural test results showed that with the addition of 0.05 GNP, only 6% increase in flexural strength was obtained, while with the addition of 0.25 wt% GNP flexural strength remained almost the same as for the neat composite. On the contrary, the addition of GNPs (1.25% by weight) causes a reduction in the flexural strength with respect to the neat composite. This was confirmed by the fractured surfaces examined by scanning electron microscope which reveals that considerable amount of fiber‐matrix debonding was observed with 1.25 GNPs loading. Dynamic mechanical analysis (DMA) revealed that the storage modulus of the neat composite increased by 12.6% with the addition of only a small amount of GNP (0.05% wt) compared to the neat composite. Composite with 1.25 GNP shows upward bending, affecting the shape of the cole–cole plot obtained from DMA results, indicating inappropriate interactions of GNPs in both the matrix and CF in the composite.

Graphene-Based Thermoplastic Composites as Extremely Broadband and Frequency-Dependent EMI Absorbers for Multifunctional Applications

Multifunctional materials are the future of modern electronics. The reduction of weight and no interfacial mismatches perfectly fit the requirements of those industry sectors which require miniaturization, low weight, and high functionality, like aerospace or wearable electronics. Here, we show multifunctional thermoplastic polymer composites based on acrylonitrile–butadiene–styrene (ABS) with graphene nanoplatelet (GNP) inclusions at different weight loadings of GNPs, from the pure polymer up to 10 wt %. The multifunctionality is expressed via efficient electromagnetic interference (EMI) shielding in an extensive frequency range, from microwave to terahertz, and good electrical conductivity and heat management. The highest measured total shielding efficiency reached over 80 dB per 1 mm-thick sample in the terahertz range for the 5 wt % GNP concentration. Composites with the highest GNP loading show high thermal conductivity of 1.8 W/mK and an electrical conductivity of 188 S/m. All composites exhibited absorption as the primary shielding mechanism. These are some of the highest EMI shielding efficiency and thermal conductivity values reported in the literature. Our results suggest that the ABS/GNP composites reported here are suitable for multifunctional EMI absorber/heat management applications.