Highly structured graphene polyethylene nanocomposites

Gąska, Karolina; Kádár, Roland; Xu, Xiangdong; Gubanski, Stanislaw; Müller, Christian; Pandit, Santosh; Mokkapati, Venkata Raghavendra Subrahmanya Sar; Mijaković, Ivan; Rybak, Andrzej; Siwek, A.; Svensson, Magnus

doi:10.1063/1.5088319

Cited by 13 publications

(11 citation statements)

References 9 publications

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“…Graphene nano‐powder (GnP) comprises single to multilayer graphite flakes and nanoplatelets with a two‐dimensional sheet of sp 2 hybrid carbon atoms, arranged like a honeycomb . This unique GnP structure provides it with high thermal conductivity, Young's modulus, electrical conductivity, and barrier properties . Consequently, it could be used to replace conventional fillers and fabricate advanced materials and technology.…”

Section: Introductionmentioning

confidence: 99%

Non‐isothermal crystallization of Ziegler Natta i‐PP‐graphene nanocomposite: DSC and new model prediction

et al. 2020

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Crystallization occurs in processing i-PP-GnP nanocomposites, and these nanocomposites have the potential to replace traditional fillers and be used to fabricate advanced materials and technology. Therefore, this subject was comprehensively investigated by applying a recent crystallization model, non-isothermal DSC experiments, Raman spectroscopy, and WAXRD. The multi-layer GnPinduced nucleation and the crystal growth rates were modelled. The overall modelling effort generated new insights, results, and explanations. This study confirmed and elucidated, or refuted several published conclusions. It has also been reported that the present model can pursue differences in catalyst-mediated i-PP backbone defects (stereo and regio) by simulating the relative crystallization profile and determining the crystallization kinetic triplet (n, k o , and E a ). The multiple roles played by GnP were underscored, which exceed what the related literature currently reports. The Raman and XRD work revealed the interaction between GnP and i-PP. The shear-induced dispersion of GnP that occurs during extrusion significantly affected i-PP crystal size distribution. The present approach can also assess the effects of catalyst type and structure, and backbone defect types and their distribution on the non-isothermal crystallization of, in general, polyolefin blends and nanocomposites.

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Section: Introductionmentioning

confidence: 99%

Non‐isothermal crystallization of Ziegler Natta i‐PP‐graphene nanocomposite: DSC and new model prediction

et al. 2020

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“…To summarize, within the present work the following procedures were found to be essential for achieving a proper dispersion and orientation of GNP in the LDPE matrix required for antibacterial effects: i) low processing temperatures—we opted for 140 °C whereas conventionally LDPE is processed at typically in the range of 160–220 °C, ii) low to no draw ratios applied—we found that draw ratios higher than 1 significantly alter the highly structured character of the nanocomposites (the draw ratio can be defined as the ratio between a linear velocity with which an extrudate is pulled and the average velocity in the extrusion die), iii) local shear rates inside the die sufficiently high in order to achieve an orientation as uniform as possible, iv) shear stresses inside the die sufficiently high for deagglomeration. While conditions (i) and (ii) had been previously investigated in highly structured LDPE–GNP films, conditions (iii) and (iv) were investigated for the first time here, especially referring to the very high GNP concentrations used, in order to adapt the extrusion process for creation of highly oriented and dispersed composites.…”

Section: Resultsmentioning

confidence: 99%

“…Due to these versatile properties and applicability for production of medical devices, we have chosen LDPE as a matrix material to mix with GNP. Considerable efforts have been previously directed at generating highly structured (oriented) GNP–LDPE nanocomposites . It has been shown that the shear flow inside an extrusion die can be utilized to induce strong orientation and uniform distribution in the flow direction.…”

Section: Introductionmentioning

confidence: 99%

Precontrolled Alignment of Graphite Nanoplatelets in Polymeric Composites Prevents Bacterial Attachment

Pandit

Gąska

Mokkapati

et al. 2020

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Graphene coatings composed of vertical spikes are shown to mitigate bacterial attachment. Such coatings present hydrophobic edges of graphene, which penetrate the lipid bilayers causing physical disruption of bacterial cells. However, manufacturing of such surfaces on a scale required for antibacterial applications is currently not feasible. This study explores whether graphite can be used as a cheaper alternative to graphene coatings. To examine this, composites of graphite nanoplatelets (GNP) and low‐density polyethylene (LDPE) are extruded in controlled conditions to obtain controlled orientation of GNP flakes within the polymer matrix. Flakes are exposed by etching the surface of GNP–LDPE nanocomposites and antibacterial activity is evaluated. GNP nanoflakes on the extruded samples interact with bacterial cell membranes, physically damaging the cells. Bactericidal activity is observed dependent on orientation and nanoflakes density. Composites with high density of GNP (≥15%) present two key advantages: i) they decrease bacterial viability by a factor of 99.9999%, which is 10 000‐fold improvement on the current benchmark, and ii) prevent bacterial colonization, thus drastically reducing the numbers of dead cells on the surface. The latter is a key advantage for longer‐term biomedical applications, since these surfaces will not have to be cleaned or replaced for longer periods.

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“…Two-dimensional nanoparticles, e.g., Graphene/GnP, can be oriented in the flow direction starting with low shear rates (e.g., as low as 10 −2 s −1 [1]). This can enable the creation of highly structured (thermoplastic in this case) polymer nanocomposites [1,18,19]. Such bulk nanocomposite morphologies exhibit anisotropic electrical and thermal properties with potential applications to field grading materials [18] and heat management components [1] as well as antibacterial properties [20].…”

Section: Methodsmentioning

confidence: 99%

“…A basic general performance requirement for nanocomposites is the filler’s mechanical reinforcing effect. In highly structured GnP-polymer nanocomposites, moderate improvements in Young’s modulus, the yield strength, and tensile strength were recorded with increasing filler concentration [1,19]. Higher values were recorded in the direction of the extrusion flow, compared to the perpendicular direction, likely due to the flow- induced molecular orientation [1].…”

Section: Methodsmentioning

confidence: 99%

A Mechanics Based Surface Image Interpretation Method for Multifunctional Nanocomposites

et al. 2019

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Graphene nanosheets and thicker graphite nanoplatelets are being used as reinforcement in polymeric materials to improve the material properties or induce new functional properties. By improving dispersion, de-agglomerating the particles, and ensuring the desired orientation of the nano-structures in the matrix, the microstructure can be tailored to obtain specific material properties. A novel surface image assisted modeling framework is proposed to understand functional properties of the graphene enhanced polymer. The effective thermal and mechanical responses are assessed based on computational homogenization. For the mechanical response, the 2-D nanoplatelets are modeled as internal interfaces that store energy for membrane actions. The effective thermal response is obtained similarly, where 2-D nanoplatelets are represented using regions of high conductivity. Using the homogenization simulation, macroscopic stiffness properties and thermal conductivity properties are modeled and then compared to the experimental data. The proposed surface image assisted modeling yields reasonable effective mechanical and thermal properties, where the Kapitza effect plays an important part in effective thermal properties.

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Highly structured graphene polyethylene nanocomposites

Cited by 13 publications

References 9 publications

Non‐isothermal crystallization of Ziegler Natta i‐PP‐graphene nanocomposite: DSC and new model prediction

Non‐isothermal crystallization of Ziegler Natta i‐PP‐graphene nanocomposite: DSC and new model prediction

Precontrolled Alignment of Graphite Nanoplatelets in Polymeric Composites Prevents Bacterial Attachment

A Mechanics Based Surface Image Interpretation Method for Multifunctional Nanocomposites

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