Did you choose the right metalworking oil emulsifier? These 7 key points must be read!
1. Emulsifier selection: from HLB value to the art of proportioning
Core Influencing Factors: The structure and type of emulsifier are crucial to emulsion performance, having a greater impact than factors like emulsification method and temperature. For example, surfactants with an HLB value (hydrophile-lipophile balance) of 3-6 are suitable for W/O emulsions, while those with an HLB value of 8-18 are suitable for O/W emulsions. Choosing the wrong type can lead to emulsion separation or failure.
HLB Difference ≤ 5: When mixing two emulsifiers, the HLB value difference should not exceed 5, otherwise stability will decrease.
Arithmetic Arrangement for More Stability: For example, mixing emulsifiers with HLB values of 6, 8, 10, and 12 in the correct proportions will yield better stability than a random combination.
Clear Prioritization: O/W emulsifiers primarily use water-soluble emulsifiers, while W/O emulsifiers primarily use oil-soluble emulsifiers. Other emulsifiers are added in a decreasing order of HLB value.
Invisible Effects of Temperature and Concentration: At high temperatures or high concentrations, the actual HLB value of an emulsifier will decrease. Therefore, the mixing ratio should be slightly higher than the theoretical required value to avoid performance degradation.
2. Water-based cutting fluid: practical analysis of 3 major types and 7 subcategories
A. Comparison of three major types:
| Type | Particle size | Advantage | Fault |
| Emulsified cutting fluid | 1-10μm | Strong cooling and low cost | Easy to corrupt, poor lubricity |
| Microemulsion cutting fluid | ＜0.1μm | High stability and long life | Oil content and extreme pressure properties need to be enhanced |
| synthetic cutting fluid | 0.01-0.1μm | Oil-free, strong cleaning | Requires additional rust protection, easy to corrode guide rails |
B. Seven sub-categories of market application scenarios:
Extreme pressure type: Contains sulfur, phosphorus, and chlorine additives and is suitable for heavy cutting (such as stainless steel machining), but copper corrosion issues should be avoided.
Microemulsion: Contains only 10-30% oil, offering greater stability than traditional emulsions and suitable for precision machining.
Fully synthetic fluid: This is an oil-free formula, but requires use with a guide rail protectant to prevent corrosion.
3. Industry Trends and Practical Case Studies
Green Transformation: Demand for bio-based emulsifiers (such as soy lecithin) will grow by 35% by 2025, reducing carbon emissions by 40% compared to traditional products.
Case Study:
Oleic acid diethanolamide: Adding 5% to copper wire drawing fluid increases the PB value to 800N while also solving the problem of wire shrinkage.
Demulsifier Selection: Xinjiang oil fields use magnetic nano-emulsifiers, which reduce wastewater oil content to less than 5mg/L and are recyclable.
Market Data: China's metalworking fluid market is expected to reach 20.6 billion yuan in 2024, with microemulsions experiencing the fastest growth rate due to their stability advantages.
4. “3 Dos and 3 Don’ts” for Emulsifier Selection
Do's: Measure HLB values, control temperature differences, and maintain the primary/secondary ratio.
Don'ts: Mix emulsifiers with vastly different polarities, ignore bacterial protection, and blindly pursue low costs.
Tip: Regularly test pH and bacterial counts, and replace any deteriorating emulsion promptly—saving a little money can lead to a big loss!
