Four Main Indexes Of Synthetic Base Oil

1. Acid value

The definition is simple, titrate the number of milligrams of KOH consumed per 1g of sample. The significance of acid value is the number of milligrams of potassium hydroxide required to neutralize free fatty acids in 1 gram ester base oil.
In the chemical reaction process of Ester Oil, it is often necessary to add excessive fatty acids to complete the reaction, and the excess acids need to be carefully removed in the post-treatment process. Acid value becomes an important index of ester oil.
We hope that no free fatty acids will be left in the ester-based oil during the process, so the acid value is required to be as low as possible. Therefore, the acid value is the embodiment of the control process precision.
When evaluating the performance of the base oil, the hydrolysis property of the ester base oil is a key point. If the acid value is too high, it means that it is easy to hydrolyze and accelerate the decline of the ester oil. Meanwhile, too much free acid will cause corrosion and oxidation and other problems.

2. Saponification value
Saponification value means the number of oil in soap. Definition: Specifies the number of milligrams of KOH required for saponification of 1g oil sample under conditions. Contrast saponification value and acid value, usually, the acid value is dealing with the skin, and saponification value means the inner, so saponification value is far more important than acid value. Saponification is equivalent to decomposing the constituent into acid + alcohol and weakening the acid. Therefore, the determination process of saponification value usually uses heating to destroy its original structure and make a saponification reaction.
If an ester oil has a fixed carbonyl number, such as trihydroxymethyl propane ester with 3 carbonyl groups, the significance of saponification value comes out. First, it can evaluate the length of fatty acid, that is, the number of carbon. If the fatty acid has a higher molecular weight, the smaller the molar ratio of 1g oil, the fewer milligrams of KOH are required, which means the lower the saponification value. Conversely, the lower the molecular weight and the lower the carbon number, the higher the saponification value. **, can evaluate the saturation, branching degree, which is also seen by molecular weight.
What about the standard of saponification value? Because of different applications, sometimes it needs to be higher, and sometimes it needs to be lower. Such as cutting fluid, saponification value is mainly reflected in the cutting fluid fatty acid or fat ester content of the general content, because only the higher the content, the subsequent need for the amount of alkali will be greater, so it is said that the higher the saponification value, the better the lubricity.

3. Iodine value

Definition, the grams of iodine that can be ingested by 100 grams of ester base oil. The higher the iodine value, the higher the unsaturated fatty acid content or the degree of unsaturated.

For example, oleic acid (1 double bond) has a lower iodine value than linoleic acid (2 double bonds), and this parameter can describe the degree of unsaturated fatty acid in the finished ester. So whether it's a free unsaturated acid or an ester, it affects the iodine number. The sulfonate value is mainly used to determine the oil and the key parameter used to judge the oil properties. For example, if the iodine value is greater than 130, the oil can be judged to be dry.

Sometimes you'll hear about bromine, especially in the PAO world. Bromine, like iodine, is an indicator of the degree of unsaturation in an organic compound. Because of molecular weight differences, bromine = iodine X0.632. In addition to this difference, bromine values are primarily targeted at petroleum hydrocarbons because bromine is more powerful and has fewer side effects.

4. Hydroxyl value
The commonly used industrial hydroxyl number refers to the number of milligrams of potassium hydroxide (KOH) equivalent to the hydroxyl group in 1g of a sample, expressed as mgKOH/g.

Hydroxyl value refers to the number of the -OH group in the product. Like the acid value, it is an important concern in the control engineering. The acid value mainly monitors the reaction of raw material acid, and the hydroxyl value is the monitoring of the reaction raw material alcohol.

The measurement of hydroxyl value is mainly based on the esterification principle of hydroxyl group, that is, the hydroxyl group in the sample is quantitatively esterified with excess acid anhydride, and the excess acid anhydride is hydrolyzed into acid and then titrated with base standard solution. Therefore, there are many factors affecting the measurement of hydroxyl value. In many base oils of metal working fluids, the hydroxyl value affects the viscosity and emulsification degree of base oils, which is a very important performance parameter.