Polyamide 6/Graphene composites: The effect of in situ polymerisation on the structure and properties of graphene oxide and reduced graphene oxide

Mechanical and Antimicrobial Properties of the Graphene-Polyamide 6 Composite

This paper presents the synthesis and characterization of graphene-polymer composites, focusing on their mechanical and antibacterial properties. Graphene flakes were obtained via an electrochemical method and integrated into polyamide 6 (PA6) matrices using melt intercalation. Various characterization techniques confirmed the quality of the graphene flakes, including X-ray diffraction (XRD), Raman spectroscopy, and infrared (IR) spectroscopy, as well as scanning and transmission electron microscopy (SEM and TEM) imaging. Mechanical tests showed an increase in the elastic modulus with graphene incorporation, while the impact strength decreased. The SEM analysis highlighted the dispersion of the graphene flakes within the composites and their impact on fracture behavior. Antimicrobial tests demonstrated significant antibacterial properties of the composites, attributed to both oxidative stress and mechanical damage induced by the graphene flakes. The results suggest promising applications for graphene-polymer composites in advanced antimicrobial materials.

Preparation of Bioactive Polyamide Fibres Modified with Acetanilide and Copper Sulphate

This paper presents a simple method of obtaining polyamide 6 fibres modified with acetanilide and copper ions. During the spinning of the fibres with the additives applied, a partial reduction of CuSO4 to Cu2+ and Cu+ ions occurs, which is observed as a change in the blue colour of the prepared polyamide granulate to the grey-brown colour of the formed fibres. CuMPs obtained as a result of the salt reduction should give the obtained fibres bioactive properties. Three types of microorganisms were selected to assess the microbiological activity of the obtained fibres, i.e., Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa and Escherichia coli. The fibres have antibacterial activity against Gram-positive and Gram-negative bacteria. The largest inhibition zones were obtained for the Gram-positive bacteria Staphylococcus aureus, ranging from 1.5 to 4.5 mm, depending on the concentration of CuMPs. The morphology of the fibres' surfaces was examined by means of scanning electron microscopy (SEM) and optical microscopy (OM). The changes in the polymer structure chemistry are studied by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray structure studies (WAXS and SAXS) and an energy-dispersive spectroscopy (EDS) analysis. The newly obtained bioactive polyamide fibres can be used in many areas, including medicine, clothing and environmental protection for the production of filters.

Hazard assessment of abraded thermoplastic composites reinforced with reduced graphene oxide

Graphene-related materials (GRMs) are subject to intensive investigations and considerable progress has been made in recent years in terms of safety assessment. However, limited information is available concerning the hazard potential of GRM-containing products such as graphene-reinforced composites. In the present study, we conducted a comprehensive investigation of the potential biological effects of particles released through an abrasion process from reduced graphene oxide (rGO)-reinforced composites of polyamide 6 (PA6), a widely used engineered thermoplastic polymer, in comparison to as-produced rGO. First, a panel of well-established in vitro models, representative of the immune system and possible target organs such as the lungs, the gut, and the skin, was applied. Limited responses to PA6-rGO exposure were found in the different in vitro models. Only as-produced rGO induced substantial adverse effects, in particular in macrophages. Since inhalation of airborne materials is a key occupational concern, we then sought to test whether the in vitro responses noted for these materials would translate into adverse effects in vivo. To this end, the response at 1, 7 and 28 days after a single pulmonary exposure was evaluated in mice. In agreement with the in vitro data, PA6-rGO induced a modest and transient pulmonary inflammation, resolved by day 28. In contrast, rGO induced a longer-lasting, albeit moderate inflammation that did not lead to tissue remodeling within 28 days. Taken together, the present study suggests a negligible impact on human health under acute exposure conditions of GRM fillers such as rGO when released from composites at doses expected at the workplace.

The Synergistic Effect of WS2 and SWNTs on Tribological Performance of Polyether MDI Polyurethane Elastomer under Dry and Wet Friction Conditions

To adapt to the complex application of polyurethane bearings, it is feasible to improve the tribological performance of single polyurethane-based friction materials through the synergistic effect produced by multi-component-lubricating fillers. In this context, rather than using tungsten disulfide (WS2), which has demonstrated excellent self-lubricating performance as a lubricating oil additive, this paper proposes that WS2 and single-walled carbon nanotubes (SWNTs) can be designed for addition into a polyether 4,4′-diphenylmethane diisocyanate (MDI) polyurethane matrix as self-lubricating fillers so as to explore the synergistic effect of micro- and nano-lubricating fillers on the tribological performance of polyurethane matrix materials. Through a series of characterizations and tests, it was found that the dispersion of two-component-lubricating additives in a polyurethane matrix is improved when the ratio of WS2 to SWNTs is roughly 2:1. In this case, the tribological performance of polyurethane matrix composites is more satisfactory than at other ratios. In addition, compared with the blank sample, the tribological performance of the synergistically modified polyurethane composites under dry friction is more significantly improved with the increase in contact load, while there is no significant improvement under water lubrication. Aside from contributing to the idea of exploring the synergistic effect of WS2 and other micro or nanofillers, this method also opens up the possibility of practically applying WS2 in the field of friction.

Thermal and Quasi-Static Mechanical Characterization of Polyamide 6-Graphene Nanoplatelets Composites

The growing demand for lightweight and multifunctional products in numerous industrial fields has recently fuelled a growing interest in the development of materials based on polymer matrices including graphene-like particles, intrinsically characterized by outstanding mechanical, thermal, and electrical properties. Specifically, with regard to one of the main mass sectors, which is the automotive, there has been a significant increase in the use of reinforced polyamides for underhood applications and fuel systems thanks to their thermal and chemical resistance. In this frame, polyamide 6 (PA6) composites filled with graphene nanoplatelets (GNPs) were obtained by melt-compounding and compared in terms of thermal and mechanical properties with the neat matrix processed under the same condition. The results of the experimental tests have shown that the formulations studied so far offer slight improvements in terms of thermal stability but much more appreciable benefits regarding both tensile and flexural parameters with respect to the reference material. Among these effects, the influence of the filler content on the strength parameter is noteworthy. However, the predictable worsening of the graphene sheet dispersion for GNPs contents greater than 3%, as witnessed by scanning electron images of the tensile fractured sections of specimens, affected the ultimate performance of the more concentrated formulation.

Graphene/graphene nanoplatelets reinforced polyamide nanocomposites: A review

Graphene and its derivatives have received considerable attention in industrial and academic research due to their unique, useful properties and applications. The use of graphene is still difficult due to its high cost of production. Hence, graphene nanoplatelets (GNPs) have been identified as a substitute for graphene, which are produced in large scale at a very low cost. Moreover, GNPs have played a significant role in various engineering thermoplastic materials [i.e., polyamides (PAs)] to enhance their properties and applications. The GNPs help in the production of low-cost multifunctional nanocomposites with notable useful properties such as high electrical conductivity, mechanical strength, and high aspect ratio. The GNPs based nanocomposites have a broad spectrum of application areas including 3D-printing, automotive materials, electrical appliances, low-cost composites films, and many more. This review summarizes different preparation techniques, properties, and applications of GNPs based PAs nanocomposites as reported in current literature.

Characterization of Polyamide 6/Multilayer Graphene Nanoplatelet Composite Textile Filaments Obtained Via In Situ Polymerization and Melt Spinning

Studies of the production of fiber-forming polyamide 6 (PA6)/graphene composite material and melt-spun textile fibers are scarce, but research to date reveals that achieving the high dispersion state of graphene is the main challenge to nanocomposite production. Considering the significant progress made in the industrial mass production of graphene nanoplatelets (GnPs), this study explored the feasibility of production of PA6/GnPs composite fibers using the commercially available few-layer GnPs. To this aim, the GnPs were pre-dispersed in molten ε-caprolactam at concentrations equal to 1 and 2 wt %, and incorporated into the PA6 matrix by the in situ water-catalyzed ring-opening polymerization of ε-caprolactam, which was followed by melt spinning. The results showed that the incorporated GnPs did not markedly influence the melting temperature of PA6 but affected the crystallization temperature, fiber bulk structure, crystallinity, and mechanical properties. Furthermore, GnPs increased the PA6 complex viscosity, which resulted in the need to adjust the parameters of melt spinning to enable continuous filament production. Although the incorporation of GnPs did not provide a reinforcing effect of PA6 fibers and reduced fiber tensile properties, the thermal stability of the PA6 fiber increased. The increased melt viscosity and graphene anti-dripping properties postponed melt dripping in the vertical flame spread test, which consequently prolonged burning within the samples.

Effect of Variation of Hard Segment Content and Graphene-Based Nanofiller Concentration on Morphological, Thermal, and Mechanical Properties of Polyurethane Nanocomposites

This study describes the development of a new class of high-performance polyurethane elastomer nanocomposites containing reduced graphene oxide (RGO) or graphene nanoplatelets (GNP). Two types of polyurethane elastomers with different contents of hard segments (HS) were used as a polymer matrix. The developed nanocomposites were characterized by thermal analysis (DSC, TG), dynamic mechanical testing (DMA), hardness testing, mechanical properties, rheology, FTIR spectroscopy, XRD, and microscopy investigation (TEM, SEM). Morphological investigation confirmed better compatibility of RGO with the polyurethane (PU) matrix compared to GNP. Both applied nanofillers influenced melting and crystallization of the PU matrix. The nonlinear viscoelastic behavior of the nanocomposites (Payne effect) was studied, and the results were compared with theoretical predictions.

Role of Stone-Wales defects on the interfacial interactions among graphene, carbon nanotubes, and Nylon 6: A first-principles study

We investigate computationally the role of Stone-Wales (SW) defects on the interfacial interactions among graphene, carbon nanotubes (CNTs), and Nylon 6 using density functional theory (DFT) and the empirical force-field. Our first-principles DFT calculations were performed using the Quantum ESPRESSO electronic structure code with the highly accurate van der Waals functional (vdW-DF2). Both pristine and SW-defected carbon nanomaterials were investigated. The computed results show that the presence of SW defects on CNTs weakens the CNT-graphene interactions. Our result that CNT-graphene interaction is much stronger than CNT-CNT interaction indicates that graphene would be able to promote the dispersion of CNTs in the polymer matrix. Our results demonstrate that carbon nanomaterials form stable complexes with Nylon 6 and that the van der Waals interactions, as revealed by the electronic charge density difference maps, play a key stabilizing role on the interfacial interactions among graphene, CNTs, and Nylon 6. Using the density of states calculations, we observed that the bandgaps of graphene and CNTs were not significantly modified due to their interactions with Nylon 6. The Young's moduli of complexes were found to be the averages of the moduli of their individual constituents.

Dispersibility of different sized graphene oxide sheets and their reinforcement on polyamide 6 fibers

PA6/grafted-SGO (g-SGO) nanocomposite fibers show improved mechanical-properties due to excellent dispersibility of g-SGO and strong interaction between g-SGO and PA6.

Impact of Silicon Nanocrystal Oxidation on the Nonmetallic Growth of Carbon Nanotubes

Carbon nanotube (CNT) growth has been demonstrated recently using a number of nonmetallic semiconducting and metal oxide nanoparticles, opening up pathways for direct CNT synthesis from a number of more desirable templates without the need for metallic catalysts. However, CNT growth mechanisms using these nonconventional catalysts has been shown to largely differ and reamins a challenging synthesis route. In this contribution we show CNT growth from partially oxidized silicon nanocrystals (Si NCs) that exhibit quantum confinement effects using a microwave plasma enhanced chemical vapor deposition (PECVD) method. On the basis of solvent and a postsynthesis frgamentation process, we show that oxidation of our Si NCs can be easily controlled. We determine experimentally and explain with theoretical simulations that the Si NCs morphology together with a necessary shell oxide of ∼1 nm is vital to allow for the nonmetallic growth of CNTs. On the basis of chemical analysis post-CNT-growth, we give insight into possible mechanisms for CNT nucleation and growth from our partially oxidized Si NCs. This contribution is of significant importance to the improvement of nonmetallic catalysts for CNT growth and the development of Si NC/CNT interfaces.

Studies of Reduced Graphene Oxide and Graphite Oxide in the Aspect of Their Possible Application in Gas Sensors

The paper presents the results of investigations on resistance structures based on graphite oxide (GRO) and graphene oxide (rGO). The subject matter of the investigations was thaw the sensitivity of the tested structures was affected by hydrogen, nitrogen dioxide and carbon dioxide. The experiments were performed at a temperature range from 30 °C to 150 °C in two carrier gases: nitrogen and synthetic air. The measurements were also aimed at characterization of the graphite oxide and graphene oxide. In our measurements we used (among others) techniques such as: Atomic Force Microscopy (AFM); Scanning Electron Microscopy (SEM); Raman Spectroscopy (RS); Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Microscopy (XPS). The data resulting from the characterizations of graphite oxide and graphene oxide have made it possible to interpret the obtained results from the point of view of physicochemical changes occurring in these structures.

Microwave-assisted ionothermal synthesis of SnSex nanodots: a facile precursor approach towards SnSe2 nanodots/graphene nanocomposites

Presented is a facile approach towards spherical SnSe₂ nanodots/graphene nanocomposites based on a microwave-assisted ionothermally synthesized nanodot precursor.

Preparation and properties of nylon 6/sulfonated graphene composites by an in situ polymerization process

Nylon 6/sulfonated graphene composites with high thermal conductivity, good mechanical properties and excellent processability were prepared using sulfonated graphene as a precursor by an in situ polymerization process.

Recent advances in graphene/polyamide 6 composites: a review

This paper reviews recent years’ (2009–2015) advances in graphene/PA6 nanocomposites for the first time.

Melt processing and characterisation of polyamide 6/graphene nanoplatelet composites

The incorporation of graphene nanoplatelets into nylon (PA6)viamelt processing on an industrial scale significantly increases the crystallinity, stiffness, and electrical conductivity of the resulting composites.

A facile route to prepare few-layer graphene/polyamide 6 nanocomposites by liquid reactive extrusion

A liquid reactive extrusion process was developed to prepare graphene/polyamide 6 nanocomposites and its crystalline and mechanical properties.