Triethanolamine is an important additive in water-based cutting fluids. Regardless of which cutting fluid is used, triethanolamine is used, indicating the importance of triethanolamine in cutting fluids. However, what role does triethanolamine play in cutting fluids? What are its functions in cutting fluids? Let's talk about the following functions of triethanolamine in cutting fluids.
1. Properties of triethanolamine Triethanolamine, also known as aminotriethanol, has a molecular formula of C6H15O3N. Triethanolamine has a wide range of industrial applications, such as in the oil and fat industry, petroleum processing industry, textile industry, rubber and environmental protection. Triethanolamine is generated by the reaction of ethylene oxide and ammonia water, and its refined product is a colorless viscous liquid. It has strong hygroscopicity and turns yellow brown in the air. Easily soluble in water and ethanol, slightly soluble in ethyl ether and benzene. PH=8-8.5, cannot evaporate with water vapor. 2. The role of triethanolamine in water-based cutting fluids 2.1 Synthesis of water-soluble oil based agents At present, most of the oil based agents with good lubrication performance are long carbon chain substances, which are mostly insoluble in water. To add them to water-based cutting fluids, hydrophilic groups must be introduced into their molecular chains. Triethanolamine has three - OH groups and good water solubility. By controlling the ratio of raw materials, one OH in the triethanolamine molecule undergoes a chemical reaction with an oily agent, resulting in the formation of a water-soluble oily agent. Oleic acid is one of the important fatty acids, but it is insoluble in water. The chemical reaction between triethanolamine and oleic acid (around 65 ℃) can generate triethanolamine oleate. It is a commonly used water-soluble oil based agent, and the higher the proportion of triethanolamine it contains, the better its water solubility. The author used a four ball testing machine to determine the maximum non seizure load PB value of the aqueous solution of triethanolamine oleate (5%), which can reach 650N. The friction coefficient was determined to be 0.071 using a friction and wear testing machine. Oleic acid triethanolamine, as an oily agent added to the cutting fluid, is prone to forming a physical adsorption film between the tool and the chip (workpiece), which plays a lubricating role at lower loads. Experiments have shown that triethanolamine oleate and extreme pressure additives also have a good synergistic anti wear effect. Adding oleic acid triethanolamine composite during the synthesis of borate and phosphate esters can significantly improve their extreme pressure lubrication performance, thereby further improving their cutting performance. 2.2 Rust inhibitor Triethanolamine itself is a water-soluble rust inhibitor. It can effectively prevent steel from rusting in the short term when used alone, with a general concentration of 0.5% to 2%. Triethanolamine has a synergistic rust prevention effect with water-soluble rust inhibitors such as phenylethanolamine, sodium benzoate, borax, and sodium carbonate. The combined use can significantly improve the rust prevention ability of water-based cutting fluids. However, triethanolamine has a corrosive effect on copper, and adding 0.05% to 0.1% benzotriazole can improve its corrosion resistance to copper. Oleic acid triethanolamine is also a rust inhibitor, which is suitable for rust prevention of ferrous metals and aluminum alloys.
2.3 Surfactants
Surfactants play a role in penetration, diffusion, stability, and cleaning in water-based cutting fluids, and are essential additives for synthesizing cutting fluids and emulsions. Triethanolamine and fatty acids can be used to synthesize an anionic surfactant. Surfactants synthesized with different ratios and fatty acids have different HLB values, which can be suitable for the needs of different water-based cutting fluids. These surfactants have good emulsification ability, and when used in combination with non ionic surfactants such as alkylphenol polyoxyethylene ether or fatty alcohol polyoxyethylene ether, the emulsification effect is better.
Triethanolamine itself is also a non ionic surfactant, and adding it to water can significantly reduce the surface tension of water. Adding triethanolamine to water-based cutting fluid will help the cutting fluid to infiltrate and penetrate the interface being cut (ground), thereby fully utilizing the cooling and cleaning effects of water-based cutting fluid.
2.4 Stabilizers
The oiliness agents, extreme pressure agents, and other additives added to water-based cutting fluids are easily resolved by water, thereby reducing the effectiveness of the cutting fluid. Adding a small amount of triethanolamine can have a stabilizing effect. For example, organic borate esters are a new type of extreme pressure and anti wear agent, which are formed by the reaction of substances with hydroxyl groups with boric acid or its compounds. The main drawback of borate esters is their ease of hydrolysis. Adding a small amount of triethanolamine during the synthesis of borate esters can inhibit hydrolysis.
3. Application of triethanolamine cutting fluids BN type water-based cutting fluid is prepared by compounding additives such as oleic acid triethanolamine, anti-wear agent (sulfur-containing borate ester), and rust prevention complex (triethanolamine, urea, borax, sodium carbonate, benzotriazole, etc.), and passing the inspection according to GB6144-85 synthetic cutting fluid standard (IV). Among them, the lubrication and rust prevention performance are superior to national standards. After long-term use by the factory, this cutting fluid has excellent performance, can significantly improve cutting efficiency and processing quality, extend tool service life, reduce processing costs, and is harmless to operators, with a long service cycle. 4. Precautions during use (1) Triethanolamine is prone to chemical reactions with nitrite to produce substances harmful to the human body. Therefore, triethanolamine cutting fluids should be carefully used with sodium nitrite as a rust inhibitor. (2) When using triethanolamine cutting fluid as grinding fluid, it will produce a slight unpleasant odor. In order to overcome this shortcoming, the addition amount of triethanolamine can be reduced, and a small amount of edible essence can also be added. (3) When grinding hard alloy tools, it is not easy to use cutting fluids containing triethanolamine. Because triethanolamine aqueous solution can leach cobalt from hard alloy cutting tools, thereby affecting their performance and lifespan.
