The widely used biodegradation test method mentioned in the previous section is the CECL-33-T-93 published by the CEC (European Cooperation Committee), which can be used to evaluate various lubricants, but it cannot reflect the ecological toxicity of degradation products.

Regarding ecological toxicity, there are two evaluation methods for the impact on animal toxicity: TM test method and Rainbow Trout Bioassay method, and plant toxicity test method for evaluating the impact on plants.

Of course, due to professional limitations, I am not very familiar with toxicity testing and biodegradation testing. Give a simple example. In the food processing industry, a considerable amount of lubricants are used in processes that directly or indirectly come into contact with food. Mineral grade food grade white oil is needed, but after all, it is mineral oil, and its degradation and ecological toxicity are issues that must be addressed. Here, vegetable oil is an ideal choice. Due to the stability of oxidation and thermal stability, synthetic oil has to be used as a compromise solution.

There is another situation, such as polystyrene, which is often used in food packaging, and the production process of polystyrene requires the addition of internal lubricants and fillers. Generally, food grade mineral white oil is also used. If considering environmental friendliness, it is also vegetable oil, and the process temperature is too high, ultimately leading to the need to switch to synthetic oil.

It can be seen that synthetic oil is an unavoidable topic when we are about to discuss environmentally friendly topics.

Of course, environmentally friendly lubricants are also composed of two main parts: additives and base oil.

The additives for green oil should be biodegradable, non-toxic, or at least not hinder the biodegradability of the base oil. Improve the performance of lubricating oil. ② Compliant with ecological requirements, low toxicity, low pollution, and biodegradable.

The German 'BLUE Angel' organization specifies lubricant additives:

1. No carcinogens.

2. No genetic mutations or distortions.

3. Free of chlorine and nitrite.

4. Does not contain metals (excluding Ca).

5. The water pollution level shall not exceed 1 (German Chemical Law).

Different base oils have different sensitivity to additives, and their biodegradability is not additive. Due to the strong polarity of the structure of vegetable oil or synthetic esters, they compete with additives for adsorption on the friction surface. Therefore, compared to mineral oil, the amount of additives added to green oil products is relatively large. For example, previous studies have shown that zinc containing anti-wear agents, detergent dispersants, and metal passivators have a significant negative impact on the biodegradation rate of vegetable oils, while certain additives containing P and N are beneficial for microbial growth and reproduction, which can improve biodegradability.

In addition, specialized sulfates, succinic acid esters, or ash free sulfates can be used as anti-corrosion agents. Ash free heterocyclic additives are a good class of multifunctional lubricant additives, and it is expected that they will have good application prospects in green lubricants.

Base oils: Apart from mineral oils, there are four main types of base oils that can be applied to green oil products. Without further explanation, the most ideal results are plant oils, as well as synthetic esters, polyethers, and polyolefins. Unfortunately, the poor oxidation stability of vegetable oil greatly limits its direct application.

Vegetable oil, commonly used as a lubricant, includes soybean oil, palm oil, rapeseed oil, sunflower seed oil, and cottonseed oil. Their main components are fatty acid glycerides (triglycerides)