Graphene Nanoplatelets Loading Research Articles

New Insights in the Nanomechanical Study of Carbon-Containing Nanocomposite Materials Based on High-Density Polyethylene

The investigation of new composite materials possessing low weight but not at the expense of their mechanical performance is of great interest in terms of reducing energy consumption in many industrial applications. This study is focused on the nanomechanical characterization of high-density polyethylene (HDPE)-based composite specimens modified with equal loadings of graphene nanoplatelets (GNPs) and/or multiwall carbon nanotubes (MWCNTs). Quasi-static nanoindentation analysis revealed the impact of the carbon nanofillers on the receiving of nanocomposites with higher nanohardness and reduced modulus of elasticity, reaching values of 0.146 GPa and 3.57 GPa, respectively. The role of the indentation size effect in elastic polymer matrix was assessed by applying three distinct peak forces. Nanoscratch experiments depicted the tribological behavior of the composite samples and inferred the influence of the carbon nanofillers on the values of the coefficient of friction (COF). It seems that the incorporation of 4 wt% GNPs in the polymer structure improves the scratch resistance of the material, resulting in a higher value of the exerted lateral force and therefore leading to the detection of a higher coefficient of friction at scratch of 0.401. A considerable pile-up response of the scratched polymer specimens was observed by means of in-situ SPM imaging of the tested surface sample area. The sway of the carbon nanoparticles on the composite pile-up behavior and the effect of the pile-up on the measured friction coefficients have been explored.

Tribological and mechanical endowments of polyoxymethylene by liquid‐phase exfoliated graphene nanofiller

AbstractIn this study, a viable route to the development of a high‐performance polyoxymethylene (POM)‐based nanocomposite is proposed to overcome tribomechanical‐related issues in high‐precision sliding parts. Prior to melt‐blending, graphene nanoplatelet (GNP) filler was processed via a series of liquid‐phase exfoliation and surface modification with 3‐aminopropyltriethoxysilane. Results indicate that GNP is successfully exfoliated with minimum defect ratio and improves interfacial bonding within the matrix. Uniform dispersion and stable load‐transfer capability of POM/GNP with 0.5 wt% loading significantly enhanced flexural, tensile and impact strength by overall 26.4%, in contrast to unfilled POM. Dry friction tests against a steel ball also showed the lowest reduction in friction coefficient and wear rate by 22% and 40.6%, respectively, at the same amount of GNP loading due to the large specific surface coverage and lubricious transfer film chelation onto the steel counterface. Furthermore, dissipated energy accumulation by friction work was calculated in the sliding interfaces based on friction force–displacement hysteresis loop where the POM/GNP 0.5 wt% wear surface consumed ca 21.7% less energy in a dry frictional shearing process compared to neat POM. However, lack or excess loading of processed GNP exhibited insufficient or poor matrix–filler adhesion and led to deterioration of the composite properties due to particle agglomeration which can cause stress concentration and serve as a failure site. The adoption of the proposed methodology would demonstrate excellent material characteristics in thin‐walled precision parts where both mechanical and tribological performances are the primary concern. © 2024 Society of Chemical Industry.

Effect of Dispersing Agents on the Electrical and Mechanical Performance of GNPs Filled Epoxy Nanocomposite

In this work, graphene nanoplatelets (GNPs) filled epoxy nanocomposites with the addition of different dispersing agents were fabricated using a method combines mechanical mixing and tip sonication. The loading of GNPs used is 0.8 vol% determined previously as the amount required to achieve the percolation threshold to conduct electricity. Three dispersing agents were used in this work: Sodium dodecyl sulphate (SDS), ethanol and Phenyl glycidyl ether (PGE), with loadings varying from 2 vol% to 10 vol%. The incorporation of dispersing agent enhanced the electrical bulk conductivity of GNPs filled nanocomposites. The mechanical performance (flexural properties and fracture toughness) of the nanocomposite were evaluated and compared. The optimum loading of SDS to obtain the highest flexural strength and fracture toughness is 2 vol%, where further increases will deteriorate the performance of nanocomposites. On the other hand, the optimum loading of ethanol and PGE are 4 vol%. The fracture toughness of GNPs filled nanocomposites improved with the addition of 2 vol% SDS and deteriorated with increasing loadings of SDS up to 10 vol%. By incorporating 4 vol% of ethanol, the optimum fracture toughness of the nanocomposite is achieved. Fracture toughness is then dropped with further increases in ethanol. The addition of PGE caused deterioration in fracture toughness of GNPs filled epoxy nanocomposite.

Graphene Nanoplatelet Induced Microphase Separation in Poly(ether-block-amide)s

The inclusion of graphene nanoplatelets (GNP) in segmented block copolymers offers a route to manipulate microphase separation for tailoring the mechanical properties of thermoplastic elastomers. GNP loading, lateral size, surface chemistry, interactions with the copolymer hard (HS) and soft (SS) segments and the relative ratio of HS:SS determine the mechanical properties achievable. To test this hypothesis, two different GNPs with similar surface chemistry but which differed in lateral dimensions by one order of magnitude (GNP1, ∼2μm and GNP2, ∼20μm) were melt mixed with three different poly(ether-block-amide)s (PE-b-A)s with variable HS and SS content from high to low. The inclusion of the larger lateral sized GNP2 had a more pronounced effect on PE-b-A morphology as it was more effective at hindering SS chain mobility resulting in microphase separation and suppression of the glass transition temperature (Tg) of the PE-b-A with the largest SS content. At low loadings GNP2 preferentially locates to the HS region, inducing reorganisation of this phase resulting in increased microphase separation. Strain induced crystallisation (SIC) phenomena were also observed for the lowest HS content PE-b-A, behaviour not evident for the PE-b-A with the largest HS content as the SS are not long enough to allow SIC. Inclusion of GNP2 to the PE-b-A with the largest HS content resulted in the largest increase in Young’s modulus (E) of 46%, tensile strength (σ) of 37% and elongation at break (ε) of 53% relative to the unfilled polymer.

Influence of graphene nanoplatelets on the thermal conductivity of heat transfer oils based on the developed hotwire method

The thermal conductivity measurements of graphene nanoplatelets (GNP) loaded mineral oil suspensions are obtained using an unconventional custom-made Transient Hot-Wire setup using tungsten. The presence of a few layers of graphene in the prepared GNP using a single-step ultrasonication of graphite microparticles without the use of a surfactant is verified by AFM, TEM, Raman Spectroscopy, XRD, and XPS techniques. We measured the thermal conductivity and the specific heat capacity ( Cp ) of GNP-loaded mineral oil suspensions. The experimental result shows a maximum of 45.5% increment in the thermal conductivity of the mineral oil with 1 mg ml−1 (11.481 ×10−4 weight fraction) loading of GNP at 30 °C. Despite thermal conductivity enhancements, the results indicate that the Cp is not compromised, since a low concentration of nanoplatelets was used. The experimental results agree with the Maxwell-Garnett effective medium approach (MGEMA) model for the thermal conductivity of nanofluids which we found to be suitable for lower loading of nanoparticles. We propose GNP incorporated mineral oil suspensions are effective when it comes to heat transfer fluids even with the lower volume and mass fractions.

Tailoring the physicochemical and dielectric properties of natural polymer using graphene nanoplatelet as filler

AbstractBio‐based flexible dielectric substrates have gained tremendous attention for their potential to reduce environmental risks from nonbiodegradable electronic waste. The present study demonstrates the fabrication of facile, nontoxic, and biodegradable chitosan‐based flexible dielectric substrate using graphene nanoplatelet (GNP) as a nanofiller. The detailed impact of different concentrations of GNP (1, 2, and 3 wt%) into the chitosan (CS) matrix was studied on physicochemical, morphological, mechanical, electrical, and thermal properties. The fabricated CS/GNP composites showed improved mechanical strength, thermal stability, and electrical properties compared with unmodified CS film. The composites exhibited excellent thermal stability (200°C) with a promising biodegradation rate (within 6 days). The mechanical strength of the unmodified CS film was increased unequivocally with 2 wt% GNP loading with tensile strength of 23.56 Mpa. Furthermore, the current–voltage (I–V) characteristic curves for CS/GNP (2%) and CS/GNP (3%) showed similar current conduction and ohmic behavior in flat, bending, and flat‐after‐bending modes. The dielectric measurements revealed that the CS/GNP composite with 2 wt% filler exhibited optimal performance having permittivity (έ) of 32.71 (at 102 Hz) with low dielectric loss of 0.04 (at 106 Hz). These results suggest that the dielectric films offer strong prospects as an eco‐friendly alternative for various applications.Highlights Biodegradable chitosan‐based flexible dielectric films were prepared. Films were made using a simple solvent casting method with 1–3 wt% GNP filler. Optimum physicochemical and electrical properties were seen at 2 wt% GNP. CS/GNP (2%) film exhibited ohmic behavior in both flat and bending modes. Excellent dielectric properties were achieved at 2 wt% GNP filler.

A study of EMI shielding efficiency, dielectric, and impedance properties of polymer nanocomposites reinforced with Graphene nanoplatelets, montmorillonite, and copper oxide nanoparticles

ABSTRACT In the present study, polyvinylchloride (PVC) and polymethyl methacrylate (PMMA) blended nanocomposites comprised of graphene nanoplatelets (GNPs), montmorillonite (MMT), and copper oxide (CuO) nanoparticles were prepared through solvent casting approach. The structural and morphological measurements confirmed the presence and dispersion of nanofillers in the polymeric chains. Thermo-gravimetric analysis (TGA) and differential-scanning calorimetry (DSC) investigations suggested the improved thermal stability for nanocomposite with 1.5 wt% GNPs loading having minimum weight loss and reduction in Tm due to the presence of GNPs, MMT, and CuO acting as a barrier to oxygen molecule diffusion and polymer-chain movement in the nanocomposite. The dielectric and impedance properties of PVC/PMMA/MMT/GNP/CuO nanocomposite investigated in 1 Hz to 20 MHz frequency range and at room temperature have shown improved dielectric constant upto 90.59 in 1 Hz frequency. The σac measures to be improved by 0.0034 (S/m) after adding GNPs, MMT, and CuO resulted from the interfacial polarization effect. The cole–cole plot investigations have shown the formation of semicircles for higher nanofiller loadings of nanocomposite. A drastic improvement in the SETotal was observed from lower to higher nanofiller concentrations. The total SE obtained for the nanocomposite with 2.5 wt% GNPs is upto 5 dB in 8–12 GHz range with absorption dominant nature of nanocomposite.

Production and mechanical characterization of Carbon fiber laminated composites modified by Graphene nano platelets (GnP) for high performance application

Polymeric materials play a pivotal role in diverse high-performance engineering domains, including aerospace, marine, automotive, and defense sectors. Their applications span from essential protective gear to intricate components vital for aircraft missiles, showcasing their versatility and significance in modern technology. The Graphene nano platelets (GnP) have the exceptional properties of a high contact area with the reinforcement material and enhanced synergistic effect, which is highly desired to improve the material performance. The present work describes the production of Carbon fiber laminated composites enhanced by Graphene nano Platelets (GnP) using a cost-effective Hand layup method (HLM). Herein, three different concentrations of GnP at 0.25, 1.0, and 1.75 wt% were used to modify the CFRP laminates. This is primarily performed to examine the viscoelastic and mechanical properties of the proposed GnP/CFRP sample. The findings of mechanical testing reveal that GnP nanofiller addition of 1.00 wt% significantly enhances the tensile and flexural properties by 20.7% and 10.05% respectively in comparison to neat sample. Also, the composites show satisfactory improvement in impact strength by 31.60% and enhanced viscoelastic properties at a 0.25 wt% of GnP loading. The XRD and DMA findings support GnP loading for high performance applications.

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 value-added conductive composite materials. This work targeted on the fabrication of melt-compounded composites via injection molding process starting from homemade recycled PET (r-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 scanning electron microscopy (SEM) investigations 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.

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.

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.