Oil is a common lubricant used in various industries for the smooth operation of machinery and equipment. Natural oils, such as vegetable and mineral oils, are often preferred due to their eco-friendliness and low toxicity. However, the delivery of these oils can be challenging as they tend to separate from water-based carriers, making them difficult to apply uniformly. Emulsifiers are commonly added to oils to overcome this problem by stabilizing the oil-in-water emulsion. However, recent studies have shown that emulsifiers can have a negative impact on the lubricating properties of oils. As a result, emulsifier-free approaches are being developed to deliver natural oils for lubrication, which can lead to better lubrication performance.
Emulsifiers are surface-active agents that have a hydrophilic (water-loving) head and a hydrophobic (oil-loving) tail. They are commonly used to stabilize oil-in-water emulsions by adsorbing at the oil-water interface and reducing the interfacial tension. This allows the oil droplets to remain dispersed in the water-based carrier, making it easier to apply. However, emulsifiers can also affect the rheological properties of oils, such as viscosity and surface tension, which can have a negative impact on lubrication performance. Emulsifiers can also form a layer on the surface of the oil droplets, reducing their ability to interact with the metal surfaces, which can lead to increased wear and friction.
Emulsifier-free approaches to oil delivery are being developed to avoid these negative effects. One such approach is the use of surfactant-free emulsions (SFEs), which are stabilized by the natural surface-active agents present in the oil. These natural surfactants, such as phospholipids and free fatty acids, can adsorb at the oil-water interface and stabilize the emulsion without affecting the rheological properties of the oil. SFEs have been shown to have superior lubrication performance compared to emulsions stabilized with synthetic emulsifiers. For example, SFEs have been used to deliver vegetable oils for metal cutting and have been found to reduce wear and friction by up to 90% compared to conventional emulsions.
Another approach to emulsifier-free oil delivery is the use of microemulsions, which are thermodynamically stable, transparent mixtures of oil, water, and surfactants. Microemulsions can be formed without the use of high-energy input, such as ultrasonication, which is often required for the formation of conventional emulsions. This makes microemulsions easier and cheaper to produce. Microemulsions can also have a smaller droplet size compared to conventional emulsions, which can lead to better coverage and penetration of the oil into the metal surfaces. Microemulsions have been used to deliver mineral oils for lubrication and have been found to have better tribological properties compared to conventional emulsions.
In conclusion, emulsifier-free approaches to oil delivery can lead to better lubrication performance compared to conventional emulsions stabilized with synthetic emulsifiers. Surfactant-free emulsions and microemulsions are two approaches that have shown promise in delivering natural oils for lubrication. These approaches can lead to reduced wear and friction, which can improve the durability and efficiency of machinery and equipment. The use of natural oils for lubrication can also reduce the environmental impact of industrial processes by reducing the use of synthetic lubricants, which are often toxic and non-biodegradable.
