Nanotechnology has real commercial potential for the textile industry. This is mainly due to the fact that conventional methods used to impart different properties to fabrics often do not lead to permanent effects, and will lose their functions after laundering or wearing.
Nanotechnology can provide high durability for fabrics, because nano-particles have a large surface area-to-volume ratio and high surface energy, thus presenting better affinity for fabrics and leading to an increase in durability of the function. In addition, a coating of nano-particles on fabrics will not affect their breath ability or hand feel. Therefore, the interest in using nanotechnologies in the textile industry is increasing.
The properties imparted to textiles using nanotechnology include water repellence, soil resistance, wrinkle resistance, antibacteria, anti-static and UV-protection, flame retardation, improvement of dye ability and so on.
What Is Fluoro Carbon?
Fluorocarbons are chemical compounds that contain carbon-fluorine bonds. The relatively low reactivity and high polarity of the carbon-fluorine bond imparts unique characteristics to fluorocarbons. Fluorocarbons tend to be only slowly broken down in the environment and therefore many are considered persistent organic pollutants. Many commercially useful fluorocarbons also contain hydrogen, chlorine, or bromine Stain and water repellency. If the critical surface tension of a solid fabric is greater than or equal to the surface tension of a liquid, the liquid will wet the fabric. If the critical surface tension of the solid is less than surface tension of the liquid, the fabric will repel the liquid.
In the case of solids 'critical surface tension' is used instead of 'surface tension'. Thus, water repellency can be attained when the critical surface tension of the solid is smaller than surface tension of the liquid. For example, when a drop of water is dripped on a cotton fabric, it has been experimentally determined that the surface tension of water and the critical surface tension of cotton are, respectively, 72 dyne/cm and 200 dyne/cm, and, therefore, water readily wets the cotton fiber. However, once the cotton is treated with a fluorocarbon the water repellent relation between them changes. The critical surface tension of water repellent finished cotton is less than the surface tension of water.
Fluorocarbons are organic compounds consisting perfluorinated carbon chain. They tend to decrease the surface tension of the substrate. Fluorocarbons generally lower the surface tensions by forming a thin film of coating around the fiber. They usually are cationic in nature but can also be non-ionic and anionic. Some useful fluorocarbons are perfluoroalkyl acrylate copolymers and their fundamental structure resembles that of acrylic resins. The surface tension of the fluorocarbon water repellent agent is extremely small, about 10 dyne/cm. Therefore, water repellency can be attained and a water drop does not adhere on the treated cotton fiber. Industry started using water repellents based on paraffin, silicone and fluorocarbons. Comparing the three systems, it was found that those belonging to the paraffin type have low water repellent effect at the initial stage and no durability to washing. Those of the silicone type were better than the paraffin-based products but were poor oil repellents. The fluorocarbon-based products were found to endow excellent oil and water repellency.
Addition of crosslinking agents along with the fluorocarbon improved the durability of water and oil repellency. Fluorocarbons can be applied in a number of ways. They can be applied by padding, kiss coating, spray, foam and exhaust. The padding method is one of the most commonly used for treating fabrics with fluorocarbons, because of the consistency and completeness of fabric coverage that can be achieved. In the case of treatment of garments with fluorocarbons, the exhaust or spray methods can be used. Treatment with fluorocarbons has to be carefully carried out, as the quality of the water and oil repellent properties are much dependent on the right kind of processing.
Crosslinking agents are indispensable for improving the durability of fluorocarbon water repellent agents. They prevent the water-repellent agents from dropping out of the fibers on washing, because they form a three dimensional network and attach the water repellent agent to the fiber. Generally, when adhering material B to the surface of material A, the more the physical properties of two materials are similar, the more strongly they adhere to each other. Generally, hydrophobic fluorocarbons strongly adhere to synthetic fibers which also are strong hydrophobic.
Therefore, good durability cannot be obtained in the case of cotton because of insufficient adhesion the hydrophilic fibers. To solve this problem and to achieve other advantages new methods have have been developed using nano technology.