With different finishing agents, water/oil repellent finishing can treat and change the surface properties of fiber materials, such as the transition of hydrophilicity and lipophilicity. Alfa Chemistry offers a range of water/oil repellent finishes to meet your high demands on the surface properties of fiber materials.
Introduction
Water-repellent finishing: The water-repellent finishing transforms the surface properties of the fiber material from hydrophilic to hydrophobic, that is, the surface tension of the fiber is lower than that of water. Water has a high surface tension (72.8 mN/m).
Oil-repellent finishing: The oil-repellent finishing changes the surface properties of the fiber material to oleophobicity, that is, the surface tension of the fiber is lower than that of the oil. Typically, oils have a surface tension of 20-40 mN/m.
Water- and oil-repellent finishing: The finishing process that forms a water- and oil-repellent surface on the fibers is called water- and oil-repellent finishing. In general, when only considering surface tension, finishes with lower surface tensions exhibit both oil and water repellency.
Antifouling finishing: On the basis of oil repellency, antifouling finishing agent has also been developed.
Surface tension of several liquids
| Type | Surface Tension /mN·m-1 | Type | Surface Tension /mN·m-1 |
|---|
| H2O | 72.8 | Carbon Tetrachloride | 26.9 |
| Nitrobenzene | 41.8 | Methanol | 22.6 |
| Benzene | 28.9 | Ethanol | 22.3 |
| Toluene | 28.4 | Acetone | 23.7 |
| Perfluoroheptane | 13.2 | Ether | 20.1 |
Typical Products
- Water Repellent Finishing Agent
Representative products of water-repellent finishing agents include metal salt finishing agents (such as paraffin-aluminum soap, aluminum acetate, aluminum formate, zirconium oxychloride), pyridine quaternary ammonium salts, metal complexes of long-chain fatty acids, organosilicon compounds, methylol melamine derivatives, organic fluorine finishing agent.
Schematic diagram of the mechanism of silicone water repellent. [1]
- Oil Repellent Finishing Agent
At present, oil-repellent finishing agents are mainly organic fluorine finishing agents, which are generally polymers containing perfluoroalkyl side chains (-CnF2n+1, n>7). Perfluorinated long-chain alkyl groups are oriented on the fiber surface, making the fiber oil-repellent, and can also be linked with acrylic acid through groups such as sulfonamide.
Mechanism And Applicability
- Water repellent and oil repellent are compounds with low surface energy groups, which can evenly coat a layer of water repellent or oil repellent molecules on the fiber surface, and form a new surface by their low surface energy, thus neither water nor oil can wet it.
- Water-repellent finishing agents can obtain sufficient water repellency by using hydrophobic aliphatic hydrocarbon compounds with a critical surface tension of about 30 mN/m, or by using a silicone finishing agent with a critical surface tension of about 24 mN/m.
- Oil-repellent finishing agents must use fluorocarbon finishing agents to reduce the critical surface tension of fibers below 15mN/m.
- In addition, the water-repellent or oil-repellent agent must be firmly attached to the surface of the fiber, and its molecular structure must also have other corresponding groups to react with the fiber or have a strong adhesion function to the fiber.
Reference
- Xiaoli Liu, et al. RSC Adv., 2019, 9, 31357-31369.
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