Techniques to Reduce Friction in Bio-Based Lubricants

Abstract Cryogenic minimum quantity lubrication systems (MQL) combine the high cooling effect of cryogenic media and the resource-efficient lubricating effect of an MQL. However, for efficient use, the cooling and lubrication properties must be precisely matched to the respective application and the load case that occurs. This article presents a tribological approach that enables the quantification of the coefficient of friction and the thermal load in frictional contact. This has shown that the use of a cryogenic MQL can significantly reduce both friction and the temperatures that occur.

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Medical device with improved lubricity for minimally invasive procedures. The device features a substrate layer, an adhesive layer containing a hydrophilic copolymer with sulfobetaine and acidic groups, and a surface lubricious layer containing hyaluronic acid or a salt thereof and a hydrophilic copolymer with sulfobetaine and acidic groups. The lubricious layer exhibits enhanced lubricity and durability in aqueous environments, reducing friction and tissue damage during insertion and movement of the device.

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In mechanical systems, lubricants play a crucial role in minimizing friction, dissipating heat, and preventing wear. Additives, comprising both organic and inorganic compounds and typically constituting 0.1% to 30% of lubricant volume, are introduced to enhance lubricant performance. This study investigates the influence of various additives on lubricant behaviour and performance, encompassing antifoam agents, corrosion inhibitors, antioxidants, detergents, extreme pressure additives, pour-point depressants, and viscosity index improvers. Friction coefficients were meticulously measured using a pin-on-disk tribometer to assess the Tribological and physical properties of these additives. Surface analysis via SEM provided insights into wear characteristics influenced by the additives. The comprehensive tribological assessment reveals that the incorporation of additives consistently reduces friction and wear across different base oil types. This underscores the critical role of additives in improving lubricant properties, maintaining thermal stability, and forming protective films on su... Read More

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Dry lubricant composition for aqueous drilling fluids, comprising a spray-dried product of neutralized carboxylic acid terminated fatty amine condensate or neutralized modified tall oil, or a mixture thereof, that reduces coefficient of friction and improves lubricity of bentonite mud while enhancing ultimate viscosity and polymer hydration efficiency.

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Lubricants must exhibit good tribological behavior at low temperatures to ensure reliable startups in very cold regions. This study investigates the performance of lubricants, with a specific focus on their capacity for high-temperature lubrication and ensuring reliable low-temperature startup in engines. Experiments were conducted to assess the friction and wear characteristics of polydiethylsiloxane in conjunction with a Si3N4 ball and M50 (8Cr4Mo4V) steel across a temperature range of 80 C to 25 C. The results indicate that the coefficient of friction, as determined through friction and wear tests at various temperatures, remained below 0.1. As temperatures progressively decreased, the systems friction coefficient increased, and wear volumes recorded at 25 C and 60 C were 9749.513 m and 105.006 m, respectively, culminating in lubrication failure at 100 C. This failure is primarily attributed to the increased viscosity and decreased mobility of polydiethylsiloxane at extremely low temperatures. Additionally, the reduced temperature increases the strength of the quenche... Read More

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The initial friction stage between the contacting materials would generate a maximum shear force and an unstable fluctuating time, which had a negative effect on the entire frictional system, especially at low temperature conditions. In order to decrease the occurring shear force and fluctuating time on the onset of friction, two different lubricating oils were applied in this study to investigate the influence of lubricants viscosity on these friction behaviors. The frictional experiments were conducted between the steel ball and the 40CrMnMo, and special attention was paid to the relationship between maximum friction force, fluctuating time, frictional vibration and the initial lubricant temperature. The results showed that the friction force first increased to the maximum value and then experienced an oscillation damping period (fluctuating time) before it reached a stable state. And this fluctuating behavior caused corresponding vibrations on the initial contacting. However, compared to the high viscosity lubricating oil (HO), the low viscosity lubricating oil (LO) contributed t... Read More

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Organisms in nature have evolved a variety of surfaces with different tribological properties to adapt to the environment. By studying, understanding, and summarizing the friction and lubrication regulation phenomena of typical surfaces in nature, researchers have proposed various biomimetic friction regulation theories and methods to guide the development of new lubrication materials and lubrication systems. The design strategies for biomimetic friction/lubrication materials and systems mainly include the chemistry, surface structure, and mechanics. With the deepening understanding of the mechanism of biomimetic lubrication and the increasing application requirements, the design strategy of multi-strategy coupling has gradually become the center of attention for researchers. This paper focuses on the interfacial chemistry, surface structure, and surface mechanics of a single regulatory strategy and multi-strategy coupling approach. Based on the common biological friction regulation mechanism in nature, this paper reviews the research progress on biomimetic friction/lubrication mater... Read More

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Abstract Applying a lubricant to the colonic mucosa and reducing the dynamic friction coefficient (DFC) between the endoscopic shaft and colonic mucosa may reduce colonoscopy invasiveness. However, the ideal lubricant viscosity remains unknown. Here, we developed a DFC measurement model integrating samples of colonic mucosa from forensic autopsy specimens into a simulated bowel bend and determined the low-friction lubricant viscosity that minimizes the DFC. Carboxymethyl cellulose, xanthan gum, hydroxyethyl cellulose, sodium alginate, and sodium polyacrylate aqueous solutions of various concentrations were used as lubricants. Low-friction lubricants minimized the load on the colonic mucosa during colonoscope insertion and reduced the total endoscopy insertion time. The highest correlation was between the DFC and the lubricant viscosity at a shear rate of 100 1/s. The lowest DFC was almost constant at approximately 0.09, irrespective of the chemical composition of the lubricant, and the low-friction lubricant viscosity (100 1/s) was 0.0310.086 (median: 0.059). The viscosities of conv... Read More

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Friction and lubrication are ubiquitous in all kinds of movements and play a vital role in the smooth operation of production machinery. Water is indispensable both in the lubrication systems of natural organisms and in hydration lubrication systems. There exists a high degree of similarity between these systems, which has driven the development of hydration lubrication from biomimetic to artificial manufacturing. In particular, significant advancements have been made in the understanding of the mechanisms of hydration lubrication over the past 30 years. This enhanced understanding has further stimulated the exploration of biomimetic inspiration from natural hydration lubrication systems, to develop novel artificial hydration lubrication systems that are cost-effective, easily transportable, and possess excellent capability. This review summarizes the recent experimental and theoretical advances in the understanding of hydration-lubrication processes. The entire paper is divided into three parts. Firstly, surface interactions relevant to hydration lubrication are discussed, encompass... Read More

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Conventional friction modifier MoDTC becomes ineffective at lower temperatures. This paper investigates the concept of "precipitation lubrication," where saturated fatty acid precipitation enhances load capacity and solid lubrication at contact points to overcome this issue. PAO8 with 4.2 % palmitic acid lubricant was prepared, precipitating below 35 C, reducing friction by approximately 14 % at 30 C for both boundary and mixed lubrication. In situ reflectance spectroscopy demonstrated palmitic acid forming a solid layer on the disk specimen, preventing direct contact between asperities and significantly reducing friction. These findings underscore the effectiveness of palmitic acid precipitation in enhancing lubrication performance at lower temperatures.

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Conventional friction modifier MoDTC becomes ineffective at lower temperatures. This paper investigates the concept of "precipitation lubrication," where saturated fatty acid precipitation enhances load-bearing capacity and solid lubrication at contact points to overcome this issue. PAO8 with 4.2 % palmitic acid lubricant was prepared, precipitating below 35 C, reducing friction by approximately 14 % at 30 C for both boundary and mixed lubrication. In situ reflectance spectroscopy demonstrated palmitic acid forming a solid layer on the disk specimen, preventing direct contact between asperities and significantly reducing friction. These findings underscore the effectiveness of palmitic acid precipitation in enhancing lubrication performance at lower temperatures.

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Minimizing the deformation caused by friction on surfaces enabled to maintain a stable friction force and coefficient of friction (COF), and valuable insights could be gained from studying bio-based lubrication systems. A natural polysaccharide was derived from fresh okras in order to enhance the lubricating efficiency of aqueous system. The lubricating performance and mechanism of okra polysaccharide were unveiled through the implementation of multiple wear tests between the steel and PA66. Particular attention was paid to the relationship between the deformation, friction force and COF. The results indicated that the surface fluctuated deformations caused comparable fluctuations in both the friction force and the COF. However, the inclusion of okra polysaccharide at a concentration of 2 wt% significantly diminished the amplitudes of friction force by decreasing surface deformations. As a result, almost 50% decrease in both COF and wear loss were observed. The lubricating mechanism of okra-polysaccharide lubricant could be described as the interaction between the hydrophilic groups ... Read More

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The evolution of lubricating oil containing additives under dynamic conditions is very significant, since its oil film structure, velocity distribution, and adsorption characteristic have an obvious impact on friction and wear. In this work, a boundary lubrication (BL) and elastohydrodynamic lubrication (EHL) models under sinusoidal load were carried out by nonequilibrium molecular dynamics (NEMD), using iron oxide as the substrate, hexadecane, and stearic acid molecules as lubricants. It was discovered that the friction in the BL regime is positively correlated with the degree of additive's solidification. The greater the solidification degree of additive layers, the less the interlacing between them, making the relative motion between them easier and reducing compression oscillation within them, thus diminishing friction in the BL regime. The degree of liquefaction of base oil and additive regions, as well as the velocity difference within their interlacing zones, are connected to the friction force in the EHL regime. At high frequencies as well as large amplitudes, the oil film ha... Read More

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Abstract Most studies of liquid lubricants were carried out at temperatures below 200 C. However, the service temperature of lubricants for aerospace and aeroengine has reached above 300 C. In order to investigate the friction mechanism and provide data for high temperature lubrication, the friction and wear properties of chlorophenyl silicone oil (CPSO)-lubricated M50 steel and Si 3 N 4 friction pairs were investigated herein. Ball-on-disk experimental results show that the lubrication performance of CPSO varies significantly with temperature. Below 150 C, coefficient of friction (COF) remains at 0.130.15 after the short running-in stage (600 s), while the COF in the running-in stage is 0.20.3. At 200 C and above, the running-in time is much longer (1,200 s), and the initial instantaneous maximum COF can reach 0.5. Under this condition, the COF gradually decreases and finally stabilizes at around 0.160.17 afterwards. This phenomenon is mainly due to the different thickness of boundary adsorption film. More importantly, the wear rate of M50 steel increases significantly with t... Read More

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The development of environmentally friendly and cost-effective lubricating materials to reduce friction and wear at macroscale is crucial for reducing fuel consumption and exhaust emissions, thereby enhancing sustainability. Deep eutectic...

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The non-renewability and and non-biodegradability of petroleum based lubricants as well as the environmental impacts their waste contributes to the environment has caused the search for a substitute for precursor of lubricant formulation. The food security issue has caused major concerns on how vegetable oil could replace petroleum based product lubricants. This paper reports the feasibility studies of kinematic viscosity, friction and wear properties of treated used cooking palm oil as precursor for development of new bio-lubricant. The treated used cooking palm oil displayed a comparable value of kinematic viscosity of 43.6cSt, coefficient of friction of 0.126 and 122m which is almost similar to the value of fresh cooking palm oil. Treated used cooking palm oil is seen to be a suitable candidate for precursor of bio-lubricant formulation, However, some additives may need to be added as to increase the tribological properties for treated used cooking oil to be used as a bio-lubricant.

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A method for creating low-friction surfaces on medical devices by incorporating oligofluorinated additives into the base polymer composition. The additives, known as surface-modifying macromolecules (SMMs), are admixed with the base polymer to form a surface with reduced coefficient of friction. The SMMs can be combined with a variety of base polymers, including polyurethanes, silicones, and polyamides, to create medical devices such as catheters, guidewires, and stents with improved lubricity. The method eliminates the need for separate coatings or liners, reducing the risk of delamination and particulate generation.

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Silicone-free, lipid/liposome-based lubricant for medical devices that eliminates particle shedding and immunogenicity risks associated with traditional silicone lubricants. The lubricant comprises liposomes with cationic lipids that break down into lamellar structures upon heat treatment, forming a stable, non-silicone coating on device surfaces. The lubricant is applied through conventional coating methods followed by thermal treatment, and can be used in place of traditional silicone lubricants in medical devices such as syringes and implants.

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Biocompatible and degradable slippery surfaces (SLIPS) and liquid-infused surfaces (LIS) that utilize lubricating liquids or emulsions to prevent fouling by microorganisms and other substances. The surfaces comprise a porous matrix of degradable polymers, such as poly(lactic-co-glycolic acid) (PLGA), that is infused with a lubricating liquid or emulsion, including vegetable oils and other biocompatible oils. The surfaces exhibit improved biocompatibility and degradability compared to conventional SLIPS and LIS, and can be fabricated using techniques such as electrospinning and solution blow spinning.

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Many laboratory tribology test machines are available for evaluating the effect of different lubricants and different operating conditions on friction. For the Mini Traction Machine (MTM) there is much published data that shows how the measured friction coefficient varies with operating conditions and lubricant type. Fully formulated lubricants containing the anti-wear additive ZDDP have often been found to have a significantly higher friction coefficient, which persists to higher speeds, compared to base oils (lubricants with no additives). Recent work has found that the surface roughness of ZDDP tribo-films can evolve to become significantly higher than that of the surfaces they are deposited on. When the measured friction coefficients of lubricants tested in the MTM machine are suitably normalized and plotted against the ratio (which is equal to the oil film thickness separating the moving surfaces divided by the combined surface roughness) then the curves for various different lubricants lie on a master curve which enables reliable friction estimates to be made for lubricated... Read More

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