Search Results (211)

The automotive industry is undergoing a transformative shift toward sustainability, driven by stringent environmental regulations, rising energy demands, and the pursuit of enhanced performance and efficiency. Lubricating materials play a pivotal role in reducing friction, wear, and energy losses in automotive systems, yet conventional lubricants, primarily petroleum-based, pose significant ecological and operational challenges. This review examines the development and performance of sustainable and advanced lubricant including bio-based oils, synthetic esters, nanolubricants, and ionic/solid lubricants for automotive applications. Drawing on tribological principles and recent advances in materials science, the article categorizes these lubricants based on source, chemical structure, and tribological behavior. A comparative framework is introduced to evaluate key performance indicators such as viscosity index, thermal stability, oxidation resistance, biodegradability, and compatibility with modern engine designs. The review also highlights emerging trends, including nanotechnology-based additives, green synthesis techniques, and novel antioxidant systems that enhance lubricant functionality and lifespan. Furthermore, a strategic research roadmap is proposed, outlining short-, medium-, and long-term priorities that integrate technical, environmental, and economic dimensions. By bridging foundational science with practical innovation, this article aims to guide researchers, manufacturers, and policymakers toward the adoption of high-performance, eco-compatible lubricants that support the transition to cleaner and more efficient mobility systems. Future directions and challenges in scaling, cost-effectiveness, and lifecycle assessment are discussed to guide innovation in this critical domain. Full article

This study introduces the preparation and tailoring of the catalytic properties of a novel biomass-based composite to produce a sustainable biolubricant, trimethylolpropane fatty acid triester (TFATE), via the transesterification of fatty acid methyl esters (FAMEs). This novel catalyst was prepared from avocado seed and chicken eggshell residues using a Taguchi experimental design to determine the best synthesis conditions. The variables tested in the catalyst preparation included CaO impregnation time and temperature, mass ratio of CaO/char, and activation temperature. The transesterification conditions to obtain TFATE were analyzed using the best eggshell-/char-based catalyst, and the reaction kinetics were measured at 120 and 150 °C. The results showed an endothermic reactive system with calculated kinetic rate constants of 7.45 × 10⁻³–10.31 × 10⁻³ L/mmol·min, and an activation energy of 15 kJ/mol. This new catalyst achieved 90% TFATE formation under optimized reaction conditions. Reuse tests indicated that catalyst deactivation occurred due to active-site poisoning, despite very low calcium leaching. Catalyst characterization confirmed the relevance of the crystalline structure and CaO loading on the avocado char surface to obtain the best catalytic properties, while ¹H nuclear magnetic resonance analysis proved TFATE formation. This low-cost catalyst can be an alternative for enhancing sustainable biolubricant production with the aim of replacing petrochemical-based counterparts. Full article

Bio-based lubricants are rapidly gaining prominence as sustainable alternatives to petroleum-derived counterparts, driven by their inherent biodegradability, low ecotoxicity, and strong alignment with global environmental and regulatory imperatives. Despite their promising tribological properties, their widespread adoption continues to confront significant challenges, particularly related to oxidative and thermal instability, cold-flow behavior, and cost competitiveness in demanding high-performance applications. This comprehensive review critically synthesizes the latest advancements in bio-based lubricant technology, spanning feedstock innovations, sophisticated chemical modification strategies, and the development of advanced additive systems. Notably, recent formulations demonstrate remarkable performance enhancements, achieving friction reductions of up to 40% and contributing to substantial CO₂ emission reductions, ranging from 30 to 60%, as evidenced by comparative life-cycle assessments and energy efficiency studies. Distinguishing this review from existing literature, this study offers a unique, holistic perspective by integrally analyzing global market trends, industrial adoption dynamics, and evolving regulatory frameworks, such as the European Union Eco-Label and the U.S. EPA Vessel General Permit, alongside technological advancements. This study critically assesses emerging methodologies for tribological evaluation and benchmark performance across diverse, critical sectors including automotive, industrial, and marine applications. By connecting in-depth technical innovations with crucial socio-economic and environmental considerations, this paper not only identifies key research gaps but also outlines a pragmatic roadmap for accelerating the mainstream adoption of bio-based lubricants, positioning them as an indispensable cornerstone of sustainable tribology. Full article

Trichilia emetica and T. dregeana butter oils are gaining recognition in the cosmeceutical industry, yet comparative data on their yields and bioactive composition remain scarce. This study assessed oil yields, fatty acid profiles, and tocol compositions of kernel and aril oils extracted by screw press from seeds collected in KwaZulu-Natal, South Africa. T. emetica produced smaller but more numerous seeds (603 per 200 g) than T. dregeana (159). Kernel oil yields were slightly higher in T. emetica (52.86%) than in T. dregeana (50.81%), while aril oils averaged 48.61% and 45.22%, respectively. Kernel oils of both species showed strong oxidative stability, with low peroxide and anisidine values and lower free fatty acid content compared to aril oils. T. emetica kernel oil was dominated by saturated fatty acids (SFAs), particularly palmitic acid (51.8%), and contained high γ-tocopherol (202 mg/kg), supporting applications in soaps, bio-lubricants, and industrial formulations. In contrast, T. dregeana kernel oil was richer in oleic acid (47.6%) and α-tocotrienol, favouring nutraceutical and cosmetic uses. Aril oils were dominated by linoleic acid (24–25%), with T. dregeana aril oil distinguished by elevated α-tocopherol (91.8 mg/kg) and a more diverse tocotrienol profile, making it suitable for antioxidant-rich cosmetics and dietary products. The dual-oil system offers complementary value: kernel oils provide structural stability for industrial applications, while aril oils supply bioactive-rich lipids for health and cosmetic formulations. Seed cakes present additional potential as biofertilizers or feedstock. This study provides the first comparative analysis of kernel and aril oils from T. emetica and T. dregeana, revealing interspecific differences in yield, fatty acid composition, and tocol profiles, and linking these to ecological adaptation and differentiated industrial potential. Full article

In this study, a green lubricating grease was prepared based on cellulose and epoxidized soybean oil (ESO). The cellulose extracted from the corn stover was functionalized using diphenylmethane diisocyanate (MDI), which enhances its compatibility and thickening ability in non-polar oil, and subsequently dispersed in ESO to form a stable gel-like bio-based grease. The functionalized surface of cellulose was characterized by FTIR, SEM, and XRD. And the rheological and tribological characteristics of the prepared bio-based grease were discussed. The superior lubricity and anti-wear properties of our bio-based grease are demonstrated by its lower friction and diminished wear relative to commercial lithium-based formulations. This work provides practical guidance for designing environmentally friendly grease for sustainable lubrication. Full article

(1) Background: Developing fully bio-based lubricating greases requires eco-friendly alternatives to conventional harmful components. This study highlights unmodified nanocellulose as an effective structuring agent in vegetable oils, enabling 100% bio-based formulations. (2) Methods: Three bio-based greases were formulated using 1.4 wt.% cellulose nanofibers (CNFs), derived from elm wood pulp through mechanical and chemical pretreatment, as thickening agents in castor oil. Their tribological performance was evaluated under varying temperatures and contact loads and compared to a reference lithium-based grease (LBG) containing 14 wt.% thickener, also formulated with castor oil. (3) Results: Among the CNFs, the unbleached variant (CNF-U) which retained the highest lignin content exhibited the highest coefficient of friction (COF), ranging from 0.09 to 0.14 across test conditions, along with a wear scar diameter of approximately 615 µm at 60 °C. Notable differences in shear stress sensitivity were observed between mechanically and chemically treated nanofibers. The TEMPO-oxidized nanofiber (CNF-TO) grease demonstrated outstanding lubrication stability across contact loads of 10–40 N and temperatures from 25 to 100 °C, maintaining COF values below 0.1—comparable to the reference LBG at 40 N load. Wear scar analysis confirmed that CNF-based greases significantly reduced wear relative to the lithium reference: CNF-B produced the smallest scar diameter (188 µm at 25 °C) while CNF-TO yielded the lowest at 60 °C (457 µm). (4) Conclusions: Nanofiber type and pretreatment significantly impact the tribological performance of CNF-based biogreases. TEMPO-oxidized CNFs provided stable lubrication under varied loads and temperatures, while all CNFs showed strong thermal adaptability, supporting their use in sustainable lubrication. Full article

Enhanced lubrication is critical for improving gear wear resistance. Current research on surface textures has overlooked the fundamental role of structural connectivity. Inspired by biological scales, a biomimetic hexagonal texture (BHT) was innovatively designed for tooth flanks, featuring dual-orientation grooves (perpendicular and inclined to the rolling-sliding direction) with bidirectional interconnectivity. This design synergistically combines hydrodynamic effects and directional lubrication to achieve tribological breakthroughs. A lubrication model for line contact conditions was established. Subsequently, the texture parameters were then optimized using response surface methodology and numerical simulations. FZG gear tests demonstrated the superior performance of the optimized BHT, which achieved a substantial 82.83% reduction in the average wear area ratio and a 25.35% decrease in tooth profile deviation variation. This indicated that the biomimetic texture can effectively mitigate tooth surface wear, thereby extending the service life of gears. Furthermore, it significantly improves thermal management by enhancing convective heat transfer and lubricant distribution, as evidenced by a 7–11 °C rise in bulk lubricant temperature. This work elucidates the dual-mechanism coupling effect of bio-inspired textures in tribological enhancement, thus establishing a new paradigm for gear surface engineering. Full article

Mineral oil-based lubricants contain harmful elements, such as sulfur and phosphorus, pose significant harm to the environment. In current research on the application of waste oils and fats in bio-based lubricants, most studies focus on single pretreatment processes or additive preparation, lacking systematic investigations into the combined use of composite pretreatment and additives on lubricant performance. Moreover, the decolorization efficiency of traditional physical adsorption methods for treating waste oils and fats is limited, making it difficult to meet the raw material requirements for bio-based lubricants. The purpose of this study is to conduct composite pretreatment processes on waste oils and fats, understand the impacts of parameters such as additive dosage and environmental factors on lubricant performance, establish an environmentally friendly and performance-compliant preparation process for bio-based lubricants, and provide a theoretical basis and technical support for its industrial application. Recent studies have shown that new decolorization processes for waste oil treatment significantly improve decolorization and recovery rates, as evidenced by research comparing new and traditional methods. Pretreatment with hydrogen peroxide, activated clay, and activated carbon significantly improved the color and odor of treated waste oil, meeting standards for bio-based lubricant production. The intercalation polymerization reaction between ethyl cellulose (EC) and montmorillonite (MMT) was employed to develop an additive (CTAB-MMT/KH560-EC). A thorough investigation was performed to analyze the impact of temperature, processing time, and additive concentration on the rheological behavior. The bio-based lubricant exhibited a kinematic viscosity of 200.3 mm²/s at 40 °C and 28.3 mm²/s at 100 °C, meeting the standard conditions as outlined in ASTM D2270-10e1. This lubricant achieved an improved low-temperature performance with a pour point of −22 °C, a friction coefficient of 0.081, and an average pitting diameter of 0.94 mm, indicating its suitability for a range of applications. These lubricants exhibit outstanding viscosity characteristics, meeting the relevant requirements for energy and environmental applications in green, eco-friendly, and biodegradable sustainable development strategies while expanding their application scope. Full article

Inside the transmission group of an agricultural tractor, the efficiency of power transfer to moving parts, their lubrication, and protection from wear are guaranteed by UTTO (Universal Tractor Transmission Oil) fluids, which are also used to operate the hydraulic system. These fluids, with mineral or synthetic origin, are characterized by excellent lubricating properties, high toxicity, and low biodegradability, which makes it important to replace them with more eco-sustainable fluids, such as those based on vegetable oils that are highly biodegradable and have low toxicity. It is also important to consider EU policies on the use of such fluids in sensitive environmental applications. To this end, several experimental bio-UTTO formulations were tested at CREA to evaluate—compared to conventional fluids—their suitability for use as lubricants for transmissions and hydraulic systems through endurance tests carried out in a Fluid Test Rig (FTR) specifically developed by CREA to apply controlled and repeatable work cycles to small volumes of oil, which are characterized by high thermal and mechanical stresses. The technical performance and the main physical–chemical parameters of the fluids were continuously monitored during the work cycles. Based on these experiences, this study describes the first application of a methodological approach aimed at testing an experimental biobased UTTO on a tractor used in normal farm activity. The method was based on a former test at the FTR in which the performance of the bio-UTTO was compared to that of the conventional UTTO recommended by the tractor manufacturer. Given the good results of the FTR test, bio-UTTO was introduced in a 20-year-old medium-power tractor, replacing the mineral fluid originally supplied, for the first reliability tests during its normal use on the CREA farm. After almost 600 h of work, the technical performance and the trend of chemical–physical parameters of bio-UTTO did not undergo significant changes. No damage to the tractor materials or oil leaks was observed. The test is still ongoing, but according to the results, in line with the indications provided by the FTR test, the experimental bio-UTTO seems suitable for replacing the conventional fluid in the tractor used in this study. Full article

Lubricants are useful for reducing the negative impacts of friction. An engine that is not properly lubricated will easily wear out, make noise, and produce excessive heat. The use of conventional petroleum-based lubricants still dominates, but the sustainability of fossil resources and the environmental impacts they have are major concerns. Therefore, the development of lubricants based on natural materials, or bio lubricants, is increasingly gaining attention. This paper aims to analyze various studies that have been conducted related to bio lubricants, especially those based on Indonesian natural resources. With the plant resources available in Indonesia, this research can be developed by utilizing the local wealth that is available, especially in abundance in Sukabumi City or Regency. Full article

This study presents a comprehensive evaluation of the tribological behavior of cylinder liners and piston rings—key components in internal combustion engines (ICEs). Experiments were conducted using a pin-on-disc wear tester under varying loads (50–100 N) and speeds (175–350 rpm) to determine the coefficient of friction (μ) and wear rate. The selected pin and disc materials represent real engine components to ensure realistic operating conditions. Before and after each experiment, the cylinder liner-piston ring pair was cleaned with acetone to ensure accurate measurement of mass loss. Surface roughness (Ra, Rq, Rz, µm) was assessed using a Mahr M-1 profilometer, and Brinell hardness tests were carried out using a digital optical Brinell hardness testing machine to determine the mechanical properties of the contact surfaces. The results revealed that safflower oil achieved the lowest coefficient of friction at higher speeds, with an 18% reduction compared with conventional 20W-50 engine oil. Camelina oil, camelina biodiesel and safflower biodiesel each exhibited a reduction of approximately 12.5% in friction, highlighting their potential as viable alternatives to petroleum-based lubricants. Full article

Rolling Bearings are crucial components for induction motors and generators in electric vehicles (EVs), as their performance considerably influences the system’s operational reliability and safety. However, the commercial greases used for bearing lubrication in EV motors pose a detrimental impact on the environment. In addition, they are ineffective in mitigating the effect of electric discharges on rolling surfaces leading to premature bearing failures. This study investigates the viability of a developed eco-friendly grease from palm olein as the base oil and glycerol monostearate as the thickener, enhanced with conductive multi-walled carbon nanotubes (MWCNTs) for EV motor bearings prone to electrical currents. Chemical–physical, tribological, and electrical tests were conducted on the developed grease samples without and with MWCNTs at 1 wt.%, 2 wt.%. and 3 wt.% concentrations and results were compared to lithium and sodium greases. Palm grease samples demonstrated a lower EDM voltage range reaching 1.0–2.2 V in case of 3 wt.% MWCNTs blends, indicating better electrical conductivity and protecting the bearing surfaces from electric-related faults. These findings were further confirmed using vibrations measurement and SEM-EDX analysis of the electrically worn bearings. Bearings lubricated with palm grease blends exhibited lower vibration levels. Palm grease with 2 wt.% MWCNTs reduced vibration amplitudes by 28.4% (vertical) and 32.3% (horizontal). Analysis of bearing damaged surfaces revealed enhanced damaged surface morphology for MWCNT-enhanced palm grease as compared to surface lubricated by commercial greases. The results of this work indicate that the proposed bio-grease is a promising candidate for future application in the field of next-generation electric mobility systems. Full article

This study evaluates the production of base oils for biolubricants using fatty acid methyl esters (FAMEs) derived from sunflower oil as the raw material. The production process involved the synthesis of oleochemical esters through a single-step alkaline transesterification reaction with a high-molecular-weight polyol, such as trimethylolpropane (TMP). To assess the effectiveness of the developed catalytic system in conducting the transesterification reactions and its impact on the properties of the final product, two types of alkaline catalysts were used. Specifically, the reactions were carried out using either Ca/TEA alkoxide or sodium methoxide as catalysts in various configurations and concentrations to determine the optimal catalyst concentration and reaction conditions. Sodium methoxide served as the commercial benchmark catalyst, while the Ca/TEA alkoxide was prepared in the laboratory. The optimal concentration of Ca/TEA was determined to be 3.0% wt. in the presence of iso-octane and 3.5% wt. under vacuum, while the corresponding concentrations of CH₃ONa for both cases were determined to be 2.0% wt. The synthesized biolubricant esters exhibit remarkable performance characteristics, such as high kinematic viscosities and low pour points—ranging from 33–48 cSt at 40 °C, 7.68–10.03 cSt at 100 °C, to −14 to −7 °C, respectively—which are comparable to or improved over those of mineral oils such as SN-150 or SN-500, with the Ca/TEA alkoxide-catalyzed systems showing superior oxidation stability and reduced byproduct formation. Full article

Vegetable oils are an important alternative to the massive use of fuels and lubricants from non-renewable energy sources. In this study, the physicochemical properties of coconut oil and waste cooking oil are investigated for biofuels and biolubricant applications. A transesterification of both oils was reached, and the transesterified oils were characterized by infrared analysis and gas chromatography. The lubricant performances of these oils have been evaluated using a ball-on-plane tribometer under an ambient atmosphere. Different formulations were developed using graphite particles as solid additive. Each initial and modified oil has been investigated as a base oil and as a liquid additive lubricant. The best friction reduction findings have been obtained for both initial oils as liquid additives, highlighting the key role of triglycerides in influencing tribological performances. Full article

The advancement of next-generation lubricants is pivotal for enhancing energy efficiency and mitigating environmental impacts across diverse industrial applications. This review systematically examines recent developments in lubricant technologies, with a particular focus on sustainable strategies incorporating bio-based feedstocks, nanostructured additives, and hybrid formulations. These innovations are designed to reduce friction and wear, decrease energy consumption, and prolong the operational lifespan of mechanical systems. A critical assessment of tribological behavior, environmental compatibility, and functional performance is presented. Furthermore, the integration of artificial intelligence (AI) into lubricant formulation and performance prediction is explored, highlighting its potential to accelerate development cycles and enable application-specific optimization through data-driven approaches. The findings emphasize the strategic role of eco-innovative lubricants in supporting low-carbon technologies and facilitating the transition toward sustainable energy systems. Full article