12 Analytical Instrumentation


contacts [21]. Lubricating greases must reduce friction and wear by providing an adequate supply of lubricant to these contact areas, preventing ingress of oxygen and moisture. Additives such as molybdenum disulfi de (MoS2) and boric acid can help reduce wear and improve protection against fretting and false brinelling [46]. These additives form protective tribofi lms on the metal surfaces, reducing friction and wear during oscillatory motion. High oil bleed rates and lower consistency greases are better suited for managing these wear conditions [23]. A high oil bleed rate ensures a steady supply of lubricant to the contact areas, preventing lubricant starvation and reducing wear. Lower consistency greases can provide better coverage protection, as they can more easily fl ow and penetrate the contact areas.


3.9 Environmental impact and biodegradability


Environmental impact and biodegradability have become increasingly important performance metrics for lubricating greases, particularly in environmentally sensitive applications such as agriculture, marine environments, and areas with strict environmental regulations. Biodegradable greases are designed to decompose through microbial activity, reducing their environmental impact and minimizing soil and water contamination. To evaluate biodegradability, the grease is subjected to controlled conditions where bacteria consume biodegradable materials, and the consumption of oxygen (O2) and release of carbon dioxide (CO2) are measured. A grease is considered biodegradable if it undergoes at least 60% degradation within 28 days, as per standard laboratory tests such as OECD 301B or OECD 301F [21]. This property is especially important for greases used in areas where environmental contamination is a concern, such as outdoor machinery, agricultural equipment, and marine applications.


The choice of base oils and additives signifi cantly infl uences a grease’s environmental impact. Vegetable oils and synthetic esters are popular choices in biodegradable formulations due to their inherent biodegradability and low toxicity. While vegetable oils offer excellent biodegradability, they may require stabilizing additives to enhance performance. Synthetic esters, on the other hand, provide superior oxidative stability and biodegradability, making them ideal for formulating environmentally friendly greases.


Beyond biodegradability, the overall environmental impact of grease also includes factors such as toxicity, eco-toxicity, and renewability of raw materials. Non-toxic additives and thickeners are preferred to minimize harmful effects on aquatic and terrestrial ecosystems. Grease formulations that utilize renewable raw materials, such as vegetable oils, contribute to resources sustainability and reduce dependence on petroleum- based products. Life-cycle assessment (LCA) further assesses a grease’s environmental impact from production to disposal. LCAs help identify areas for improvement, such as reducing energy consumption during manufacturing, optimizing formulations for longer service life, and ensuring proper disposal and recycling of used greases [47].


With the growing focus on sustainability, research and development efforts are continuously directed towards formulating even more environmentally friendly lubricating greases. Advancements in base oil technology, thickener design, and additive development aim to further improve biodegradability, performance, and overall environmental impact.


4 Challenges and Future Research


Directions The development of sustainable and high-performance lubricating greases has made notable strides, yet several challenges continue to hinder widespread adoption and optimization. These challenges necessitate ongoing research and innovation to strike a balance between performance and sustainability, cater to application-specifi c needs, ensure long-term stability, maintain cost-effectiveness, and establish standardized testing methodologies.


4.1 Balancing performance and sustainability


One of the foremost challenges in the formulation of sustainable greases lies in balancing performance characteristics with environmental compatibility. Traditional greases often rely on petroleum-based thickeners and additives, which are effective but pose environmental concerns. Sustainable alternatives must maintain or even enhance key performance parameters such as consistency, thermal stability, and corrosion resistance, while also offering


PIN OCTOBER / NOVEMBER 2024 improved biodegradability and reduced toxicity.


Future research should prioritize the development of novel bio-based thickeners that can rival or surpass the performance of conventional metallic soap thickeners. Furthermore, enhancing the oxidative and thermal stability of vegetable oil-based formulations without compromising their biodegradability is crucial. Exploring the synergistic effects between bio-based components and additives could lead to formulations that achieve optimal performance across multiple parameters, ensuring that sustainable greases do not compromise on quality or functionality.


4.2 Addressing application-specifi c requirements


Different industries present unique lubrication challenges that sustainable grease formulations must address. For instance, high-temperature applications in the aerospace industry or high-pressure environments in offshore drilling require specialized greases that can withstand extreme conditions. Similarly, sensitive ecosystems, such as marine environments or agricultural applications, demand biodegradable greases that minimize environmental impact while providing reliable performance.


Research in this area should focus on tailoring sustainable grease formulations to meet the rigorous demands of specifi c applications. This could involve developing specialized biodegradable greases for use in sensitive ecosystems or improving the noise-reduction capabilities of eco-friendly greases for precision machinery and consumer products. Addressing these application-specifi c requirements will be essential for the broader adoption of sustainable greases across various industries.


4.3 Ensuring long-term stability and service life


Another challenge for sustainable greases, particularly those based on bio-derived components, is ensuring long-term stability and extended service life. Traditional petroleum- based greases often exhibit superior oxidative and hydrolytic stability, contributing to their durability. However, bio-based alternatives may be more susceptible to degradation over time, which can limit their effectiveness in demanding applications.


Research efforts should focus on improving the oxidative and hydrolytic stability of bio-based greases, extending their useful life without compromising their environmental benefi ts. Developing more effective antioxidant and anti-wear additives that are both environmentally friendly and compatible with bio-based components is another priority. Also, investigating the impact of various environmental factors, such as temperature fl uctuations and exposure to moisture, on the long-term performance of sustainable greases will provide valuable insights for formulation improvement.


4.4 Achieving cost-effectiveness and scalability


For sustainable greases to gain widespread market acceptance, they must be cost-competitive with traditional petroleum-based products. The high cost of bio-based components and the complexity of their production processes currently pose signifi cant barriers to large-scale adoption.


To overcome these challenges, research should focus on optimizing production processes for bio-based components, thereby reducing manufacturing costs. Exploring alternative sources of renewable raw materials could also ensure a stable and affordable supply chain. Furthermore, developing innovative formulation techniques that maximize performance while minimizing the use of costly additives will be essential in making sustainable greases economically viable for a broad range of applications.


4.5 Establishing standardization and testing methodologies.


As the fi eld of sustainable grease formulations continues to evolve, the lack of standardized testing methodologies and performance criteria remains a signifi cant challenge. Without standardized methods, it is diffi cult to compare the performance and environmental impact of different formulations, hindering industry-wide adoption.


Research in this area should aim to develop and validate new test methods specifi cally designed for bio-based and sustainable grease formulations. Establishing industry-wide standards for evaluating the environmental impact and


sustainability of lubricating grease is crucial for ensuring consistency and reliability in product assessments. Additionally, creating comprehensive life-cycle assessment tools tailored to sustainable grease formulations will provide a more accurate understanding of their overall environmental footprint.


5 Conclusion


By addressing these challenges and focusing research on these key areas, the lubricating grease industry can make signifi cant progress toward more sustainable and high- performance products. This will not only meet the growing demand for environmentally responsible lubrication solutions across various sectors but also contribute to the global effort to reduce the environmental impact of industrial processes.


References


[1] P. Baart, P. M. Lugt, and B. Prakash, “Contaminant Migration in the Vicinity of a Grease Lubricated Bearing Seal Contact,” Journal of Tribology, vol. 133, no. 4, 2011, doi: 10.1115/1.4004958.


[2] A. K. Jain and A. Suhane, “Capability of biolubricants as alternative lubricant in industrial and maintenance applications,” Int. J. Curr. Eng. Technol, vol. 3, no. 1, pp. 179-183, 2013.


[3] A. Z. Syahir et al., “A review on bio-based lubricants and their applications,” Journal of Cleaner Production, vol. 168, pp. 997-1016, Dec. 2017, doi: https://doi.org/10.1016/j. jclepro.2017.09.106.


[4] R. Shah, R. Chen, and M. Woydt, “The Effects of Energy Effi ciency and Resource Consumption on Environmental Sustainability,” Lubricants, vol. 9, no. 12, p. 117, 2021. [Online]. Available: https://www.mdpi.com/2075- 4442/9/12/117.


[5] T. Panchal, D. Chauhan, M. Thomas, and J. Patel, “Bio based grease A value added product from renewable resources,” Industrial Crops and Products, vol. 63, pp. 48-52, Jan. 2015, doi: https://doi.org/10.1016/j. indcrop.2014.09.030.


[6] P. M. Lugt, “Modern advancements in lubricating grease technology,” Tribology International, vol. 97, pp. 467-477, May 2016, doi: https://doi.org/10.1016/j. triboint.2016.01.045.


[7] J. Salimon, N. Salih, and E. Yousif, “Biolubricants: Raw materials, chemical modifi cations and environmental benefi ts,” European Journal of Lipid Science and Technology, vol. 112, no. 5, pp. 519-530, 2010, doi: https:// doi.org/10.1002/ejlt.200900205.


[8] H. Hybská, J. Mitterpach, D. Samešová, M. Schwarz, J. Fialová, and D. Veverková, “Assessment of ecotoxicological properties of oils in water,” Archives of Environmental Protection, vol. 44, no. 4, pp. 31-37, 2018.


[9] S. Vafaei, M. Jopen, G. Jacobs, F. König, and R. Weberskirch, “Synthesis and tribological behavior of bio-based lubrication greases with bio-based polyester thickener systems,” Journal of Cleaner Production, vol. 364, p. 132659, Sep. 2022, doi: https://doi.org/10.1016/j. jclepro.2022.132659.


[10] N. N. Dube, M. ElKady, H. Noby, and M. G. A. Nassef, “Developing a sustainable grease from jojoba oil with plant waste based nanoadditives for enhancement of rolling bearing performance,” Scientifi c Reports, vol. 14, no. 1, p. 539, Jan. 2024, doi: 10.1038/s41598-023-50003- 9.


[11] Y. Singh, A. Farooq, A. Raza, M. A. Mahmood, and S. Jain, “Sustainability of a non-edible vegetable oil based bio-lubricant for automotive applications: A review,” Process Safety and Environmental Protection, vol. 111, pp. 701-713, Oct. 2017, doi: https://doi.org/10.1016/j. psep.2017.08.041.


[12] S. Z. Erhan and S. Asadauskas, “Lubricant basestocks from vegetable oils,” Industrial Crops and Products, vol. 11, no. 2, pp. 277-282, Mar. 2000, doi: https://doi. org/10.1016/S0926-6690(99)00061-8.


[13] R. Kreivaitis and M. Gumbytė, “Investigation of mixture of vegetable oil and synthetic esters as environmentally friendly base stock for low-temperature lubrication applications,” Tribology in Industry, vol. 40, no. 3, p. 401, 2018.


[14] B. Khemchandani, A. K. Jaiswal, E. Sayanna, and M. Forsyth, “Mixture of saffl ower oil and synthetic ester as


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