Poly(ether ether ketone) composites reinforced by short carbon fibers and zirconium dioxide nanoparticles: Mechanical properties and sliding wear behavior with water lubrication

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.

Tribological Properties of Oil-in-Water Emulsion with Carbon Nanocapsule Additives

An experimental investigation was performed on the coefficients of friction (COFs) and wear properties of pure water and oil-in-water (O/W) working fluids containing carbon nanocapsules (CNCs) with concentrations ranging from 0 to 1.0 wt.%. For the O/W working fluid, the ratio of oil to water was set as 6%. It was shown that for the water working fluid, the COF decreased by around 20% as the CNC content increased from 0 to 1.0 wt.%. In contrast, the wear volume increased by 50% as the CNC addition increased from 0 to 0.5 wt.%, but it fell to a value slightly lower than that achieved using only pure water (i.e., no CNCs) as the CNC content was further increased to 1.0 wt.%. For the O/W emulsion, the addition of 0.8 wt.% CNCs reduced the COF by around 30% compared to that of the emulsion with no CNCs. Overall, the results showed that while the addition of a small quantity (6%) of oil to the water working fluid had a relatively small effect on the wear performance, the addition of an appropriate quantity of CNCs (i.e., 0.8 wt.%) resulted in a significantly lower COF and an improved wear surface.

Poly (ether ether ketone) composites reinforced by graphene oxide and silicon dioxide nanoparticles

Wear-resistant composites with excellent tribological performances and good mechanical/thermal properties were developed by blending the modification of nano-silicon dioxide (m-SiO2) and the modification of graphene oxide (m-GO) with a poly (ether ether ketone) (PEEK) matrix by twin-screw extrusion compounding and subsequently injection molding. The tribological behaviors and the mechanical/thermal properties of the composites were carefully investigated. Compared with pure PEEK, PEEK/m-GO, and PEEK/m-SiO2 composites, the PEEK/m-GO/m-SiO2 composites exhibited considerable enhancements in those performances. These were attributed to m-GO and m-SiO2 that carried the majority of the load during a sliding process and prevented severe wear of the matrix.

Enhancement of the tribological properties of carbon fiber/epoxy composite by grafting carbon nanotubes onto fibers

Morphology of CF before and after grafting CNT; wear resistance of CF/EP composite.

Nano-TiO2 reinforced PEEK/PEI blends as biomaterials for load-bearing implant applications

Biocompatible ternary nanocomposites based on poly(ether ether ketone) (PEEK)/poly(ether imide) (PEI) blends reinforced with bioactive titanium dioxide (TiO2) nanoparticles were fabricated via ultrasonication followed by melt-blending. The developed biomaterials were characterized using FT-IR, SEM, XRD, DSC, TGA, and DMA. Further, their water-absorption, tensile, tribological, dielectric, and antibacterial properties were evaluated. PEI acts as a coupling agent, since it can interact both with PEEK via π-π stacking and polar interactions as well as with the nanoparticles through hydrogen bonding, as corroborated by the FT-IR spectra, which resulted in a homogeneous titania dispersion within the biopolymer blend without applying any particle surface treatment or polymer functionalization. A change from promotion to retardation in the crystallization rate of the matrix was found with increasing TiO2 concentration, while its crystalline structure remained unaltered. The nanoparticles stiffened, strengthened, and toughened the matrix simultaneously, and the optimal properties were achieved at 4.0 wt % TiO2. More interesting, the tensile properties were retained after steam sterilization in an autoclave or exposure to a simulated body fluid (SBF). The nanocomposites also displayed reduced water absorption though higher thermal stability, storage modulus, glass transition temperature, dielectric constant, and dielectric loss compared to the control blend. Further, remarkable enhancements in the tribological properties under both SBF and dry environments were attained. The nanoparticles conferred antibacterial action versus Gram-positive and Gram-negative bacteria in the presence and the absence of UV light, and the highest inhibition was attained at 4.0 wt % nanoparticle concentration. These nanocomposites are expected to be used in long-term load-bearing implant applications.

Inorganic Nanoparticle-Modified Poly(Phenylene Sulphide)/ Carbon Fiber Laminates: Thermomechanical Behaviour

Carbon fiber (CF)-reinforced high-temperature thermoplastics such as poly(phenylene sulphide) (PPS) are widely used in structural composites for aerospace and automotive applications. The porosity of CF-reinforced polymers is a very important topic for practical applications since there is a direct correlation between void content and mechanical properties. In this study, inorganic fullerene-like tungsten disulphide (IF-WS₂) lubricant nanoparticles were used to manufacture PPS/IF-WS₂/CF laminates via melt-blending and hot-press processing, and the effect of IF-WS₂ loading on the quality, thermal and mechanical behaviour of the hybrid composites was investigated. The addition of IF-WS₂ improved fiber impregnation, resulting in lower degree of porosity and increased delamination resistance, compression and flexural properties; their reinforcement effect was greater at temperatures above the glass transition (T_g). IF-WS₂ contents higher than 0.5 wt % increased T_g and the heat deflection temperature while reduced the coefficient of thermal expansion. The multiscale laminates exhibited higher ignition point and notably reduced peak heat release rate compared to PPS/CF. The coexistence of micro- and nano-scale fillers resulted in synergistic effects that enhanced the stiffness, strength, thermal conductivity and flame retardancy of the matrix. The results presented herein demonstrate that the IF-WS₂ are very promising nanofillers to improve the thermomechanical properties of conventional thermoplastic/CF composites.