WEAR BEHAVIOR OF CARBON NANOTUBE/HIGH DENSITY POLYETHYLENE COMPOSITES

Multi-Walled Carbon-Nanotube-Reinforced PMMA Nanocomposites: An Experimental Study of Their Friction and Wear Properties

This manuscript presents an experimental investigation of the friction and wear properties of poly (methyl methacrylate) (PMMA) nanocomposites reinforced with functionalized multi-walled carbon nanotubes (MWCNTs). The aim of this study is to evaluate the potential of MWCNTs as a reinforcement material for enhancing the tribological performance of PMMA. Three types of multi-walled carbon nanotubes, i.e., pristine, hydroxyl functionalized, and carboxyl functionalized, were utilized in this study. The nanocomposite samples were prepared by dispersing varying concentrations of MWCNTs (0.1 wt.%, 0.5 wt.%, and 1 wt.%) within the PMMA matrix via a 3D mixing approach, followed by injection molding/compression molding. The resulting nanocomposite films were characterized using scanning electron microscopy (SEM) to observe the dispersion of MWCNTs within the PMMA matrix. The friction and wear tests were conducted using a pin-on-disk tribometer under dry sliding conditions. The effects of functionalization and MWCNT content on the tribological behaviors of the nanocomposites were analyzed. The nanocomposites exhibited lower friction coefficients and reduced wear rates compared to pure PMMA. The lowest friction coefficient and wear rate were achieved at an optimum MWCNT loading of 0.5 wt.%. It was further revealed that the amount of MWCNT reinforcement, average load, and track diameter significantly affect the coefficient of friction (COF) and rate of wear. The COF and wear rate are best at a filler loading of 0.5 wt.%, a 20 Kg load, and 90 mm. The improved tribological performance of the MWCNT-reinforced PMMA nanocomposites can be attributed to the effective transfer of load between the MWCNTs and the PMMA matrix, as well as the reinforcement effect of the MWCNTs. The MWCNTs acted as reinforcing agents, enhancing the mechanical properties and wear resistance of the nanocomposites.

Research Trends in Carbon Chain Polymers and Their Derivatives: Highlighting the Decade-Long Research

Polyolefins include low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), and polybutylene (PB). Polyolefins offer unique characteristics such as chemical resistance, smooth surface, re-shapability, and are lighter than glass and metal-based materials. The global plastics industry produces polyolefin as their major product and these polyolefins are mostly used as commercial commodity plastics. Moreover, the characteristics of polyolefin can be further improved by forming their blends and/or composites and incorporating fillers. This review highlights the role of various fillers such as titanium dioixde-based, nitride-based, and carbon-based nanomaterials, in influencing polyolefin composites. Moreover, the contribution of layered double hydroxide in olefin polymerization, and the impact of filler properties such as filler content, filler type, filler phase stability, and synergistic effect between the fillers and polymers on nanocomposites are discussed.

A molecular dynamics study on the mechanical properties of defective CNT/epoxy nanocomposites using static and dynamic deformation approaches

In this paper, the mechanical behavior of epoxy polymer nanocomposite with continuous single-walled carbon nanotubes (SWCNT) with and without vacancy defects has been investigated based on two approaches of deformation, molecular mechanics (static) and molecular dynamics. In this regard, molecular simulation has been performed on the basis of the compass force field. In order to validate the research steps, the results obtained for pure epoxy polymer were compared with similar molecular dynamic simulations, which confirmed the simulation process. The research process proposed a method for controlling the symmetry of the system during equilibration with an asymmetric barostat. The Souza-Martins barostat was also used to apply loading and deformation control over a constant strain rate range. The results showed that in both deformation approaches (with and without calculating the contribution of kinetic energy), the presence of defects improved the transverse tensile and shear moduli, while the longitudinal tensile modulus decreased. Also, the improvement and decrease of the longitudinal tensile modulus and longitudinal shear modulus of the nanocomposite in comparison with the net polymer have been observed in both approaches, respectively. As a general result, it was observed that the contribution of kinetic energy has a major effect on the mechanical properties of pristine and defective nanocomposites.

Carbon Nanotube Reinforced High Density Polyethylene Materials for Offshore Sheathing Applications

Multiwall carbon nanotube (CNT)-filled high density polyethylene (HDPE) nanocomposites were prepared by extrusion and considered for their suitability in the offshore sheathing applications. Transmission electron microscopy was conducted to analyse dispersion after bulk extrusion. Monolithic and nanocomposite samples were subjected to accelerated weathering and photodegradation (carbonyl and vinyl indices) characterisations, which consisted of heat, moisture (seawater) and UV light, intended to imitate the offshore conditions. The effects of accelerated weathering on mechanical properties (tensile strength and elastic modulus) of the nanocomposites were analysed. CNT addition in HDPE produced environmentally resilient nanocomposites with improved mechanical properties. The energy utilised to extrude nanocomposites was also less than the energy used to extrude monolithic HDPE samples. The results support the mass substitution of CNT-filled HDPE nanocomposites in high-end offshore applications.

Toxicity of Carbon Nanotubes as Anti-Tumor Drug Carriers

Nanoparticle drug formulations have enormous application prospects owing to achievement of targeted and sustained release drug delivery, improvement in drug solubility and reduction of adverse drug reactions. Recently, a variety of efficient drug nanometer carriers have been developed, among which carbon nanotubes (CNT) have been increasingly utilized in the field of cancer therapy. However, these nanotubes exert various toxic effects on the body due to their unique physical and chemical properties. CNT-induced toxicity is related to surface modification, degree of aggregation in vivo, and nanoparticle concentration. This review has focused on the potential toxic effects of CNTs utilized as anti-tumor drug carriers. The main modes by which CNTs enter target sites, the toxicity expressive types and the factors affecting toxicity are discussed.

Bulk Oriented UHMWPE/FMWCNT Films for Tribological Applications

Bulk oriented films based on ultrahigh molecular weight polyethylene (UHMWPE) with a drawing ratio of 35 were prepared by using a low solvent concentration. Bulk oriented films were filled with fluorinated multi-walled carbon nanotubes (FMWCNTs). The structure of bulk oriented films on UHMWPE, which were manufactured at different stages of orientation, was investigated by scanning electron microscope (SEM) and differential scanning calorimetry (DSC). The addition of FMWCNTs at a concentration of 0.05 wt % in bulk oriented UHMWPE films led to an increase in the tensile strength by 10% (up to 1020 ± 23 MPa) compared to unfilled oriented films. However, the addition of FMWCNTs at a concentration of more than 0.5 wt % led to a decrease in tensile strength due to excessive accumulation of nanotubes and hindering of self-diffusion of UHMWPE macromolecules. The multiple increase in tensile strength, doubling the hardness, the formation of fibrillar structure, and the presence of carbon nanotubes led to a significant increase in tribological properties in bulk oriented films. Bulk oriented UHMWPE/1% FMWCNT films can be operated at a maximum contact pressure that is 18 times higher and exhibit a specific wear rate more than an order of magnitude and less than the traditional UHMWPE of isotropic structure. Bulk oriented UHMWPE/1% FMWCNT films have an extremely low dry coefficient of friction (COF) of 0.075 at a contact pressure of 31 MPa. The developed bulk oriented films can be used for manufacturing frictional surfaces for sliding bearings, or for acetabular cups for knee and hip endoprostheses.

Nanotechnology for Food Packaging and Food Quality Assessment

Nanotechnology has paved the way to innovative food packaging materials and analytical methods to provide the consumers with healthier food and to reduce the ecological footprint of the whole food chain. Combining antimicrobial and antifouling properties, thermal and mechanical protection, oxygen and moisture barrier, as well as to verify the actual quality of food, e.g., sensors to detect spoilage, bacterial growth, and to monitor incorrect storage conditions, or anticounterfeiting devices in food packages may extend the products shelf life and ensure higher quality of foods. Also the ecological footprint of food chain can be reduced by developing new completely recyclable and/or biodegradable packages from natural and eco-friendly resources. The contribution of nanotechnologies to these goals is reviewed in this chapter, together with a description of portable devices ("lab-on-chip," sensors, nanobalances, etc.) which can be used to assess the quality of food and an overview of regulations in force on food contact materials.

Graphene oxide/carboxyl-functionalized multi-walled carbon nanotube hybrids: powerful additives for water-based lubrication

A novel additive, GO/CNTs hybrids, has been developed for water-based lubrication.

Wear of Carbon Nanofiber Reinforced HDPE Nanocomposites Under Dry Sliding Condition

High density polyethylene (HDPE) is widely used as a bearing material in industrial application because of its low friction and high wear resistance properties. Carbon nanofiber (CNF) reinforced HDPE nanocomposites are promising materials for biomedical applications as well, such as being the bearing materials in total joint replacements. The main objective of the present study is to investigate how the wear of HDPE can be altered by the addition of either pristine or silane treated CNFs at different loading levels (0.5 wt. % and 3 wt. %). Two types of silane coating thicknesses, 2.8 nm and 46 nm, were applied on the surfaces of oxidized CNFs to improve the interfacial bonding strength between the CNFs and the matrix. The CNF/HDPE nanocomposites were prepared through melt mixing and hot-pressing. The coefficients of friction (COFs) and wear rates of the neat HDPE and CNF/HDPE nanocomposites were determined using a pin-on-disc tribometer under dry sliding conditions. The microstructures of the worn surfaces of the nanocomposites were characterized using both scanning electron microscope (SEM) and optical microscope to analyze their wear mechanisms. Compared with the neat HDPE, the COF of the nanocomposites were reduced. The nanocomposite reinforced with CNFs coated with the thicker silane coating (46 nm) at 0.5 wt. % loading level was found to yield the highest wear resistance with a wear rate reduction of nearly 68% compared to the neat HDPE.

STUDIES ON MECHANICAL PROPERTIES OF CARBON NANOTUBES/HIGH-DENSITY POLYETHYLENE NANOCOMPOSITES BY SMALL PUNCH TECHNIQUE

Carbon nanotubes have been used as a reinforcing element to improve the properties of polymer matrix. An attempt has been made to investigate the mechanical behavior of carbon nanotubes–high-density polyethylene (CNT–HDPE) nanocomposites using a small punch technique. The designed punch assembly was fabricated and mounted on the Universal Testing Machine. The experimental setup was calibrated using aluminum and mild steel where the relative error was found to be within 7%. The mechanical properties of the nanocomposites, were studied by varying the weight fraction of CNT in HDPE. It was found that Young's modulus and ultimate strength of nanocomposites were increased by 37% and 36%, respectively for 1 wt% of CNTs in HDPE and they were found to increase linearly with an increase in CNT concentration. It is concluded that the small punch technique was successfully developed and tested to characterize the mechanical properties of HDPE and CNT–HDPE nanocomposites.

Preparation and Properties of Recycled Polypropylene /Carbon Nanotube Composites

Recycled polypropylene (PP)/carbon nanotube (CNTs) composites with different CNTs fraction were prepared by the melting blend method. The effects of CNTs content on the thermal properties and mechanical properties were mainly investigated. The results show that the thermal degradation of the composites shifts towards higher temperatures as the concentration of CNTs is increased. With increasing CNTs content, tensile strength and elongation at break increase firstly and then decrease. When CNTs content is 3 %, tensile strength and elongation at break are 34.71 and 27.00, respectively. Moreover, a unique tensile rupture characteristic was found by SEM observations, which explained the critical broken theory of the PP/CNTs composites.