Can lubricants also get sunburned?
author: Leila
2024-07-18
Will lubricants be affected by the sun? Will lubricants get "sunburned" in the sun? Will the color of lubricants darken after being exposed to the sun affect their performance?
The answer is yes. Long-term exposure to the sun will not only "tan" the lubricant, but also affect its performance. Therefore, lubricants must be waterproof and dustproof outdoors, as well as sun-proof.
Lubricants should avoid long-term exposure to the sun, which will accelerate oxidation and even shorten the service life of the lubricant, and fail before the recommended oil change period. From a molecular level, under long-term exposure to ultraviolet rays from the sun, the reaction between the long-chain hydrocarbons in the oil and oxygen intensifies, forming chromophores (a mixture of aldehydes, ketones and esters), which absorb visible light and present a yellow to brown appearance depending on the concentration. Therefore, lubricants should be avoided from being exposed to the sun for a long time, especially when the sun is strong.
Cause analysis:
Compared to visible light, the ultraviolet light in sunlight has a shorter wavelength and higher energy, which can break chemical bonds, so many materials including our skin, plastics and oils (especially mineral oils) will be affected. Therefore, if lubricating oil is placed outdoors, transparent containers should be avoided.
The following is a comparative test of turbine oil placed outdoors. PET bottles and glass bottles were used to store the oil. After 5 days of exposure to sunlight, the color of the oil was obviously observed to darken. Similar changes occurred in the oils in both bottles.
The degree of deterioration of the oil in the above experiment was analyzed by high pressure differential scanning calorimetry (PDSC) and rotary pressure vessel test (RPVOT). The results showed that the acid value and viscosity increased slightly, and the antioxidant properties of some oil samples were significantly reduced.
The degree of deterioration of the oil in the above experiment was analyzed by high pressure differential scanning calorimetry (PDSC) and rotary pressure vessel test (RPVOT). The results showed that the acid value and viscosity increased slightly, and the antioxidant properties of some oil samples were significantly reduced.
The same control test was conducted indoors, using fluorescent lamps and sunlight through UV-proof glass to irradiate the lubricating oil. The results showed that the lubricating oil did not change color.
Conclusion: Ultraviolet rays will affect the performance of lubricating oil in the short term and weaken the antioxidant properties of lubricating oil. Therefore, lubricating oil should be protected from direct exposure to ultraviolet rays or sunlight.
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