Literature Study of the Potential Natural Oil Extracts from Plants as Bio Lubricants Using Local Resources in Indonesia ^†

Abstract

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.

1. Introduction

Lubricants are an important part of a mechanical component. When operating, a mechanical system moves at a very high speed. When moving, these components rub against each other. 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. Base oil as a lubricant can reduce friction between two surfaces of components. As the engine operates, the base oil experiences a deterioration in performance [1,2]. This is caused by high temperatures due to long-term friction.

To address this issue, additives are incorporated into the base oil to enhance its physical and chemical properties. These additives, which include friction modifiers, thickeners, anti-corrosive agents, and dispersants, play a crucial role in improving the overall performance of the lubricant [3]. The additives themselves that are widely developed come from derivatives of hydrocarbon compounds. The use of conventional petroleum-based lubricants still dominates, but the sustainability of fossil resources and the environmental impacts they cause are major concerns. Therefore, the development of lubricants based on natural materials, or bio lubricants, is increasingly gaining attention as an environmentally friendly and sustainable alternative.

Indonesia, as a country with high biodiversity, has great potential in the development of bio lubricants from natural plant oil extracts. Local resources, such as palm oil, castor oil, coconut oil, and nyamplung oil (tamanu oil), have been widely studied as natural lubricant base materials because they have better tribological properties, such as stable viscosity, a high viscosity index, and better biodegradability properties, compared to petroleum-based lubricants [4,5,6,7].

However, the development of bio lubricants using local resources still faces various challenges, including oxidation stability, high-temperature resistance, and compatibility with wider industrial applications. Therefore, a literature review on the potential of using vegetable oil extracts as bio lubricants needs to be conducted to understand their characteristics, advantages over conventional lubricants, and opportunities and challenges in implementation in Indonesia.

2. Methods

The articles that were reviewed are 20 articles taken from the Science Direct database using the keywords “Bio Lubricant” and “Additives”. Based on the articles taken, the results of research using additives from plant extracts were selected, in detail showed in Figure 1. The information taken from these research journals takes the form of additives used, extraction methods applied, tribology tests, wear tests, and SEM/metallography microstructures.

The criterium for the plants studied are types of plants that can be found in Indonesia.

3. Results and Discussion

Based on the journals used as review material, several zeolite synthesis methods were obtained, which are shown in

Table 1. Bio-lubricant materials and synthesis methods.

No	Author	Materials	Methods
1	Li Chen [8]	Cotton leaves	Ultrasound-assisted alkaline leaching.
2	Li Chen [9]	Corn cobs	Alkali extraction using ultrasonic
3	Samuel Gemsprim Muthurathinam [10]	Vegetable oil	Transesterification mixed with SAE 20W40 base oil
4	Pranav Prasannakumar [11]	Cashew nut skin	Etherification and evaporator
5	Yashvir Singh [12]	Michelia champaca	Distillation and evaporator

Corn cob polymerization with a binary copolymer (PN) and a ternary copolymer (PFN) was conducted by detecting the absorption characteristics of the C=C group. In addition, a chemical shift in the range of 6.82–6.90 ppm by the benzene ring showed that the polymerization of the PFN was successful. In Nuclear Magnetic Resonance (NMR) spectroscopy analysis of cotton leaves, the functional groups -C=CH₂ appear in the ranges δ 5.50–6.20 ppm and 6.40–6.45 ppm, while the characteristic peak of C=C disappears, which means this spectrum indicates that polymerization was also successful. Based on the results obtained, polymerization can be identified using NMR spectroscopy, Ultraviolet-Visible Spectroscopy (UV-VIS), and Fourier Transform Infrared (FTIR) [13].

As for oil extracted from plants, it is also necessary to test to determine the content of oil. One of them used Thin-Layer Chromatography (TLC). The anacardic acid content in raw cashew nuts reached 60–65%, while those that are steamed first showed a content of only 5%. This method was used to find out whether the extracted oil contains a lot of peroxide. These peroxide compounds have oxidative properties. Therefore, a smaller content is very good as a bio lubricant because its oxidation stability is good [14].

Some other tests conducted after the synthesis process are viscosity and density tests. The viscosity of the lubricating oil itself varies, and this can depend on the mechanical system that is used. For example, for automotive purposes, the expected viscosity is 30–120 cSt, while gears require 240 cSt. The viscosity of oil from cashew nut shells is 115.65 ± 1.12 at a temperature of 40 °C. While Tamanu plant-based oil has a viscosity of 3.39–104.26, which is suitable for metalworking applications [15,16].

Based on the journals used as review material, several tribological and wear test methods were documented, which are shown in

Table 2. Tribological and wear surface tests from previous research.

Authors	Tribological Test	Wear Surface
Li Chen [8]	The coefficient of friction (CoF) decreases with the addition of cotton leaf.	Wear surfaces lubricated with polymer-based lubricants show shallower wear marks and more surface roughness.
Li Chen [9]	Does not provide long-term stable friction-reducing and anti-wear effects at lower concentrations	Significantly reduces wear volume (98.17%) and surface roughness (97.63%)
Samuel Gemsprim Muthurathinam [10]	Biolubricant mixtures, such as N10, P10, P20, and N20, are able to reduce wear by 77%, 52%, 92%, and 81%, respectively.	Vegetable oils have darker shades caused by corrosive wear due to oxidation. The surface morphology shows that the wear surface of the bio lubricant has almost a similar wear pattern to SAE20W40.
Pranav Prasannakumar [11]	The Mechanical Extracted Cashew Nut Shell Oil (MEO) sample has a higher coefficient of friction (CoF) than Solvent Extracted Cashew Nut Shell Oil (SEO). This may be due to the presence of anarcardic acid in SEO.	Not observed
Yashvir Singh [12]	Addition up to a concentration of 0.6% showed a reduction in the friction effect.	Epoxidized Michelia Champaca oil indicated the surface was found smoother, and there is no delamination of the layers.

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Cotton leaf extract contains polymeric compounds with claw-like molecular structures that exhibit lubricating properties similar to those of synthetic polymer additives. A high concentration of these high-molecular-weight additives can effectively reduce shear damping during frictional interactions. This claw-shaped polymer structure is influenced by the presence of lone electron pairs on oxygen atoms within the ester and ether functional groups. These groups facilitate strong interactions with metal surfaces, promoting robust adsorption, and subsequently reducing the shear strength at the contact interface [17]. Additives in bio lubricants can increase the oxidation period of oil. The shear stress experienced by base oil initiates free radicals in a chain, so oil undergoes self-oxidation, destroying the polymer structure. A longer oxidation period means that this process can be prevented from happening because the phenol compound will maintain a stronger structure [18].

In addition, bio lubricants based on vegetable oil contain a lot of fatty acids. The long chain structure of this compound affects the thickness of the adsorbed layer; the longer the chain is, the wider the protected area is, and the more protective it is [19]. Another mechanism that can occur in bio lubricants, such as Michelia Champaca oil and other epoxy plants, is that the -O- group forms a cross-link bond on the metal surface so that it can protect by forming a lubricating layer [20].

4. Conclusions

The development of additives as biolubricants can help researchers create more environmentally friendly substitutes. 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. All the additives used show good capabilities, but durability over long periods and under high temperatures is still lacking. Some testing methods that can be conducted in similar research in the future using local materials are UV-VIS, FTIR, NMR spectroscopy, and viscosity testing. These tests are carried out to determine the physicochemical properties of the bio lubricant material being studied. In addition, other tribolological tests can be carried out using a four-ball friction tester, which can be compounded upon by surface morphology imaging after testing. Using these two types of test, answers can then be drawn regarding the lubrication mechanism of the biolubricant that has been made.