Lubricants

Research

22 pages, 10829 KiB

Open AccessArticle

Preparation and Tribological Behaviors of Antigorite and Wollastonite Mineral Dual-Phase-Reinforced Polytetrafluoroethylene Matrix Composites

by Chen Wang, Helong Yu, Yanli Yin, Xinyuan Zhou, Hongmei Wang, Zhanyong Song, Shen Wang, Zhe Yang and Zhimin Bai

Lubricants 2024, 12(3), 74; https://doi.org/10.3390/lubricants12030074 - 26 Feb 2024

Viewed by 905

Abstract

Research on polymer matrix composites with excellent tribological properties has received increasing attention in recent years. In this study, antigorite and wollastonite mineral dual-phase-reinforced polytetrafluoroethylene (PTFE) matrix composites were prepared by filling PTFE with mineral powders using ball-milling, cold-pressing, and pressureless sintering methods. [...] Read more.

Research on polymer matrix composites with excellent tribological properties has received increasing attention in recent years. In this study, antigorite and wollastonite mineral dual-phase-reinforced polytetrafluoroethylene (PTFE) matrix composites were prepared by filling PTFE with mineral powders using ball-milling, cold-pressing, and pressureless sintering methods. The phase structure, microstructure, chemical composition, Shore hardness, and tribological behavior of the composites rubbed against steel balls under dry friction conditions were investigated. The results show that the composites have a dense structure and uniform distribution of mineral phases, with a Shore hardness of 62–68.8, an increase of 18.7–23.7% compared to pure PTFE. Compared with the addition of mono antigorite or wollastonite, the composites prepared by simultaneously filling the two minerals exhibited excellent tribological properties. The average friction coefficient and wear volume of the (10Atg + 20Wl)/PTFE composites were reduced by 44.2% and 71.4%, respectively, compared to those of pure PTFE. A dense and continuous tribofilm composed mainly of SiO₂, MgSiO₃, Mg₂SiO₄, MgO, CaO, CaMg(SiO₃)₂, and CaF₂ was formed on the worn surfaces of both the dual-phase-reinforced PTFE matrix composites and counterpart steel balls during the friction process. The reduction in friction and wear is attributed to the reinforcement effect of the minerals on the PTFE matrix as well as the complex physical and chemical reactions at the friction interface stimulated by the synergistic effects between the two minerals. The addition of wollastonite reduced the phase transition temperature of antigorite, promoting more tribochemical reaction products with good abrasion resistance and friction-reducing properties, which contributed to the excellent tribological behavior of the composites. Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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17 pages, 6560 KiB

Open AccessArticle

Self-Lubricating Properties of Polyether-Ether-Ketone Composites Filled with CNTs@RC2540 Nano-Capsules

by Jiju Guan, Zhengya Xu, Lei Zheng, Lanyu Yang and Shuiquan Huang

Lubricants 2023, 11(12), 511; https://doi.org/10.3390/lubricants11120511 - 01 Dec 2023

Cited by 1 | Viewed by 1503

Abstract

Polyether-ether-ketone (PEEK) exhibits great potential in being a replacement for metal components across various applications relying on the mechanical and tribological properties. However, there is still much to be done to improve its properties. The main motivation of this paper is to improve [...] Read more.

Polyether-ether-ketone (PEEK) exhibits great potential in being a replacement for metal components across various applications relying on the mechanical and tribological properties. However, there is still much to be done to improve its properties. The main motivation of this paper is to improve the tribological and mechanical properties of PEEK simultaneously for more severe working environment. Therefore, dialkyl pentasulfide (RC2540) was proposed to fill into the cavity of CNTs to prepare nano-capsules, which were then filled into PEEK to prepare PEEK/nano-capsules composites. The existence of nano-capsules in PEEK was analyzed, and the friction and wear properties exhibited by PEEK composites against GCr15 steel were examined using pin-disk friction pairs, and the self-lubricating mechanism of PEEK composites in friction was revealed. Findings of this study indicated that when the mass fraction of nano-capsules was less than 5%, the filling of nano-capsules could improve the tensile strength of PEEK and reduced the friction coefficient and specific wear rate of PEEK by filling nano-capsules. During the friction process, RC2540 in the nano-capsules can be released as PEEK wears so that a self-lubricating layer can be formed for reducing PEEK composites’ friction and wear. Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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12 pages, 2322 KiB

Open AccessArticle

In Vitro Wear Behavior of Knee Implants at Different Load Levels: The Impact of the Test Fluid

by Stefan Schroeder, Maximilian Uhler, Mareike Schonhoff, Timo A. Nees, Tanja Wonerow, Jens Nuppnau, Frank Mantwill and Jan Philippe Kretzer

Lubricants 2023, 11(11), 474; https://doi.org/10.3390/lubricants11110474 - 04 Nov 2023

Viewed by 1006

Abstract

Calf serum is defined as a test fluid for in vitro knee wear simulation studies in the ISO standard. However, protein degradation typically occurs during in vitro wear simulation. The current study should indicate whether increased loads change the rheological properties of the [...] Read more.

Calf serum is defined as a test fluid for in vitro knee wear simulation studies in the ISO standard. However, protein degradation typically occurs during in vitro wear simulation. The current study should indicate whether increased loads change the rheological properties of the test fluid and may, therefore, lead to favorable tribological behavior and reduced wear. Three different load levels were simulated in a displacement-controlled knee wear simulation study. The gravimetric wear rates were determined, pressure measurements were performed, and the dynamic viscosity of the test fluids were analyzed after the simulation of 0.5 × 10⁶ cycles. The lowest load level led to the lowest wear rate, and the lowest contact pressure and contact area, compared to the medium and high-load level. Although, the high-load level led to the highest contact pressure and contact area, the wear rates were comparable to the medium-load level. The rheological measurements revealed the highest dynamic viscosity for the high-load level and no differences could be found between the medium and low loading condition. To perform realistic wear simulation studies, the reproduction of the in vivo interrelationships between the shear forces and wear are necessary. Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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12 pages, 4576 KiB

Open AccessArticle

Effect of h-BN and Nano-SiO₂ Fillers on the High-Temperature Tribological Properties of PEEK/PI-Based Composites

by Mengjiao Li, Jingjing Yang, Shengqi Ma, Gang Liu, Hongru Yang and Jianan Yao

Lubricants 2023, 11(10), 416; https://doi.org/10.3390/lubricants11100416 - 22 Sep 2023

Viewed by 818

Abstract

PEEK is being used increasingly often in seals, bushings, bearings, and other moving parts due to its excellent mechanical and tribological properties. Herein, PEEK-based composites were prepared using PI as the organic filler and h-BN and nano-SiO₂ particles as the inorganic fillers. [...] Read more.

PEEK is being used increasingly often in seals, bushings, bearings, and other moving parts due to its excellent mechanical and tribological properties. Herein, PEEK-based composites were prepared using PI as the organic filler and h-BN and nano-SiO₂ particles as the inorganic fillers. There was significant improvement in the tribological properties of PEEK at conditions above the glass transition temperature; the coefficient of friction of +20P/4B/4Si was stabilized at 0.06 at 200 °C and the wear rate was reduced by 60% compared to PEEK. The role played by the thermal conductivity of h-BN and the promotion of friction transfer film by nano-SiO₂ in improving the tribological properties of PEEK is illustrated. The modified composites exhibited stable mechanical and tribological properties over a wide temperature range, which is instructive for instrumentation and testing applications in harsh environments. Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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14 pages, 6158 KiB

Open AccessArticle

Effect of Oxygen and Moisture on the Friction and Wear of Carbon Fiber-Reinforced Polymers

by Pontus Johansson, Pär Marklund, Marcus Björling and Yijun Shi

Lubricants 2023, 11(9), 412; https://doi.org/10.3390/lubricants11090412 - 20 Sep 2023

Cited by 1 | Viewed by 974

Abstract

Carbon fiber-reinforced polytetrafluoroethylene (CF/PTFE) composites are frequently used in tribological dry gas applications, such as in dynamic seals in reciprocating hydrogen gas compressors and Stirling engines, due to their superior friction and wear. Due to the increasing concerns regarding fluoropolymers as possible pollutants [...] Read more.

Carbon fiber-reinforced polytetrafluoroethylene (CF/PTFE) composites are frequently used in tribological dry gas applications, such as in dynamic seals in reciprocating hydrogen gas compressors and Stirling engines, due to their superior friction and wear. Due to the increasing concerns regarding fluoropolymers as possible pollutants of harmful per- and poly-fluoroalkyl substances (PFAS) emissions, replacements for PTFE should be investigated. The literature indicates that CF-reinforced polyetheretherketone (CF/PEEK) may have similar favorable tribological properties to CF/PTFE. However, the tribological behavior of CF/PEEK in dry gas is poorly understood, and no direct comparison has been made between the two materials. The aim of this study was to compare the effect of oxygen and moisture on the friction and wear of CF/PTFE and CF/PEEK. Tribological tests were carried out with a tri-pin-on-disc tribometer in a nitrogen environment with individually controlled contents of oxygen and moisture. The results showed that the effect of oxygen and moisture are distinctly different for CF/PTFE and CF/PEEK. While CF/PTFE performs best in oxygen-deficient environments, CF/PEEK performs best in moisture-enriched environments. Complementary tests with a PTFE composite filled with both CF and PEEK suggested that the environmental sensitivity can be significantly reduced by combining the two polymers. Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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13 pages, 2815 KiB

Open AccessArticle

Surface Laser Micropatterning of Polyethylene (PE) to Increase the Shearing Strength of Adhesive Joints

by Szymon Tofil, Piotr Kurp and Manoharan Manikandan

Lubricants 2023, 11(9), 368; https://doi.org/10.3390/lubricants11090368 - 31 Aug 2023

Viewed by 688

Abstract

In the introduction, we present an overview of previous research on this subject in order to help the reader review possible technological solutions regarding the joining of construction materials. The original research presented in this article concerns the results of increasing the shear [...] Read more.

In the introduction, we present an overview of previous research on this subject in order to help the reader review possible technological solutions regarding the joining of construction materials. The original research presented in this article concerns the results of increasing the shear strength of adhesive joints of plastics using various types of surface preparation (laser texturing). Laser texturing consists in developing the surface by applying various geometric patterns of appropriate shapes and depths, as well as its density on the surface. The above parameters are currently selected in an empirical way as research is still being developed as part of a research project. The textures obtained in this way are subjected to microscopic examination. Then, a layer of glue is applied, and the samples prepared in this way, after drying, are subjected to various destructive tests, e.g., tensile, shear, and bending. In this article, we attempted to test the strength of the bonded joint of polyethylene (PE). The impact of a laser beam with ultrashort picosecond pulses was used in the research. Tools in the form of a TRUMPF TruMicro 5325c device integrated with a SCANLAB GALVO scanning head were used. This enabled ablative material removal without the presence of a heat affected zone (HAZ) in the non-laser part. Ultrashort laser pulses remove material without melting the non-exposed area by the laser beam. On the basis of the tests performed (in this article and previous research works of the authors), it was shown that the method increases the shear strength of the glued joints made in the tested construction materials. This is confirmed by laboratory results of tribological tests. The laser treatment parameters used, which are shown in this article, did not lead to the appearance of cracks in the micromachined materials. Research has shown that the connections between elements with a properly selected micropattern are characterized by a several-fold increase in the strength of joints, unlike materials without a micropattern. The presented method may be helpful for use as a technology for joining plastics. Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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19 pages, 3912 KiB

Open AccessArticle

Polymer Dispersion Effects on Drag, Heat Transfer, and Mass Transfer in Non-Newtonian Based Nanofluids

by Ayesha Sahreen, Adeel Ahmad, Razi Khan and Rab Nawaz

Lubricants 2023, 11(8), 339; https://doi.org/10.3390/lubricants11080339 - 09 Aug 2023

Cited by 2 | Viewed by 812

Abstract

This article explores the influence of polymers on the boundary layer flow, heat transfer, and mass transfer control of non-Newtonian-based nanofluids flowing past a stretching surface. The mathematical model incorporates the Oldroyd-B model to analyze the effects of polymers, while the Powell–Eyring and [...] Read more.

This article explores the influence of polymers on the boundary layer flow, heat transfer, and mass transfer control of non-Newtonian-based nanofluids flowing past a stretching surface. The mathematical model incorporates the Oldroyd-B model to analyze the effects of polymers, while the Powell–Eyring and Reiner–Philippoff viscosity models are employed to study the behavior of non-Newtonian fluids. The dispersion model is adopted to account for nanofluid characteristics. Appropriate transformations yield governing equations with similar forms, which are solved numerically to investigate the impact of polymer inclusion on skin friction, Nusselt number, and Sherwood number. The study’s findings reveal that the addition of polymers to the non-Newtonian-based nanofluids leads to a reduction in heat and mass transport while enhancing skin drag. Detailed analysis of these effects sheds light on the underlying physical mechanisms. Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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12 pages, 10637 KiB

Open AccessArticle

Friction and Wear Characteristics of Bacterial Cellulose Modified by Microcellular Foaming Process

by Jin Hong, Jae-Ho Han, Doyeon Kim, Gukhyeon Yun, Kwan Hoon Kim and Sung Woon Cha

Lubricants 2023, 11(8), 322; https://doi.org/10.3390/lubricants11080322 - 31 Jul 2023

Viewed by 987

Abstract

Bacterial cellulose (BC) is a biodegradable, non-toxic, natural substance that can be obtained by culturing bacteria. It can be approached in various ways from physical, chemical, and biological points. BC nanoparticles have been applied as lubricating additives to improve the load capacity, anti-wear, [...] Read more.

Bacterial cellulose (BC) is a biodegradable, non-toxic, natural substance that can be obtained by culturing bacteria. It can be approached in various ways from physical, chemical, and biological points. BC nanoparticles have been applied as lubricating additives to improve the load capacity, anti-wear, and friction. The microcellular foaming process was created using a technology based on the saturation of the polymer by supercritical CO₂ and rapid decompression. An increase in saturation pressure leads to an increase in the molecular potential energy of CO₂, which can be more easily compressed into the cellulose matrix. Moreover, the high crystallinity and water content combination contribute to thermal stability. Specimen membranes produced by Komagataeibacter xylinus prepared with a thickness of 2 mm were saturated in supercritical condition, 10 MPa of CO₂ for 4 h, and foamed at a temperature of 120 °C in a hot press. After the foaming process, we used dry ice to cool the BC. Before foaming, the friction coefficient continuously increased with the increase in cycles, and after foaming, a stable friction coefficient of 0.3 or less was secured despite the increase in the cycle. The microcellular foaming process significantly reduced and made BC’s coefficient of friction stable. Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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17 pages, 20306 KiB

Open AccessArticle

Tribological and Micro-Mechanical Properties of Injected Polypropylene Modified by Electron Radiation

by Martin Ovsik, Michal Stanek and Adam Dockal

Lubricants 2023, 11(7), 296; https://doi.org/10.3390/lubricants11070296 - 15 Jul 2023

Cited by 1 | Viewed by 822

Abstract

Today, more and more importance is given to the improvement of polymer materials’ wear resistance, i.e., their micro-mechanical and tribological properties, which could widen their application in practice. The properties of materials can be modified by several methods, among them exposure to electron [...] Read more.

Today, more and more importance is given to the improvement of polymer materials’ wear resistance, i.e., their micro-mechanical and tribological properties, which could widen their application in practice. The properties of materials can be modified by several methods, among them exposure to electron radiation. This study focuses on the effect of varying radiation intensity (15 kGy to 99 kGy), depth of penetration, and subsequent structure modification of injection-molded polypropylene on tribological and micro-mechanical properties. Electron radiation influences the structure of individual layers, thus improving or degrading their properties. Hence, the depth of penetration can be examined by instrumented hardness tests and scratch tests. Due to irradiation, surface properties and wear resistance increased by up to 105% (from 38 MPa to 78 MPa). As the results show, an increase in mechanical properties was recorded in the direction towards the center of the sample (from 72 MPa to 82 MPa). Micro-mechanical tests were also confirmed by the observation of cross-linking changes (gel test) as well as crystallinity increases (wide-angle X-ray diffraction and microtome cuts). This finding could have a significant effect on the manufacturing and subsequent modification of injection-molded polypropylene parts, which opens new possibilities in practice for this material. The increased surface wear resistance enables the use of parts for which the durability and abrasion resistance of the surface are demanded, especially in applications facing exposure to long-term cyclical loads (e.g., gears). Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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20 pages, 7349 KiB

Open AccessArticle

Frictional Response of Reinforced Polymers under Quasistatic and Fast-Transient Dry Contact Conditions

by Davide Tonazzi, Etienne Betsch, Alexandre Pages and Francesco Massi

Lubricants 2023, 11(5), 202; https://doi.org/10.3390/lubricants11050202 - 30 Apr 2023

Viewed by 1484

Abstract

Reinforced polymers have recently gained interest because of their high stiffness associated with the classical features and cost-effectiveness of polymers. A further characteristic, suitable for several applications, is the possibility to provide high frictional and wear resistance. The frictional response of commercially available [...] Read more.

Reinforced polymers have recently gained interest because of their high stiffness associated with the classical features and cost-effectiveness of polymers. A further characteristic, suitable for several applications, is the possibility to provide high frictional and wear resistance. The frictional response of commercially available reinforced materials was here investigated in a wide range of contact boundary conditions. Experimental tests were performed on different test benches, to investigate the material frictional response under either quasistatic or fast-dynamic contact solicitations. While carbon-fiber-reinforced material exhibits a stable but low friction coefficient, the glass-fiber-reinforced material leads to the suitable combination of high friction and low wear. The PPS material, 40% (wt) glass-reinforced polymer, sliding against the Ti6Al4V titanium alloy, provided high static friction coefficients (>0.4). The same material pair was then tested in endurance under fast-dynamic contact solicitations, highlighting their resistance to wear. Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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17 pages, 3575 KiB

Open AccessArticle

Physical Analysis of Thermophoresis and Variable Density Effects on Heat Transfer Assessment along a Porous Stretching Sheet and Their Applications in Nanofluid Lubrication

by Zia Ullah and Musaad S. Aldhabani

Lubricants 2023, 11(4), 172; https://doi.org/10.3390/lubricants11040172 - 10 Apr 2023

Cited by 4 | Viewed by 1193

Abstract

Nanofluids are engineered colloidal suspensions of nanoparticles in the base fluids. At very low particle concentration, nanofluids have a much higher and strongly temperature-dependent thermal conductivity, which enables them to enhance the performance of machining applications such as the cooling and lubrication of [...] Read more.

Nanofluids are engineered colloidal suspensions of nanoparticles in the base fluids. At very low particle concentration, nanofluids have a much higher and strongly temperature-dependent thermal conductivity, which enables them to enhance the performance of machining applications such as the cooling and lubrication of the cutting zone during any machining process, the vehicle’s braking system, enhanced oil recovery (EOR), engine oil, and the drilling process of crude oil. In the current work, the density is assumed as an exponential function of temperature due to larger temperature differences. The main focus of this mechanism is the variable density effects on heat and mass characteristics of nanoparticles across the stretching porous sheet with thermophoresis and Brownian motion to reduce excessive heating in high-temperature systems. This is the first temperature-dependent density problem of nanofluid across the stretching surface. The coupled partial differential equations (PDEs) of the present nanofluid mechanism are changed into nonlinear coupled ordinary differential equations (ODEs) with defined stream functions and similarity variables for smooth algorithm and integration. The changed ODEs are again converted in a similar form for numerical outcomes by applying the Keller Box approach. The numerical outcomes are deduced in graphs and tabular form with the help of the MATLAB (R2013a created by MathWorks, Natick, MA, USA) program. In this phenomenon, the velocity, temperature, and concentration profile, along with their slopes, have been plotted for various parameters pertaining to the current issue. The range of parameters has been selected according to the Prandtl number

0.07 \leq P r \leq 70.0

and buoyancy parameter

0 < λ < \infty

, respectively. The novelty of the current work is its use of nanoparticle fraction along the porous stretching sheet with temperature-dependent density effects for the improvement of lubrication and cooling for any machining process and to reduce friction between tool and work piece in the cutting zone by using nanofluid. Moreover, nanoparticles can also be adsorbed on the oil/water surface, which alters the oil/water interfacial tension, resulting in the formation of emulsions. Full article

(This article belongs to the Special Issue Tribology of Polymer-Based Composites)

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