HOW FLUOROCARBONS WORK?

Principle-If the critical surface tension of solid is more than the surface tension of liquid, then liquid will wet the solid. So if the critical surface tension of solid is reduced than that of liquid, the water repellency can be achieved. And the effect can be imparted on fabric by using fluorocarbons, which are the carbon compounds containing perfluorinated carbon chain. They form thin film around the fibre and as they possess a very low surface tension of around 10dyne/cm, the drop does not adhere to the surface fibres.

LIMITATION:

• Good durability cannot be obtained for cotton.
• Fluorine compounds may cause skin related problems.
• Effect will reduce after few washes.

To overcome these problems new methods have been developed using nanotechnology.

The manufacturing of self-cleaning textiles using nanotechnology:-

• Using Photo catalyst
• Using microwaves
• Using carbon nanotubes
• Using Metal oxide colloidal
• Using silver nanoparticles
• Using chlorine halamine

1.       Using Photo catalyst

Starting with photocatalysts. It is catalytic self-cleaning process. In this process Nano-sized , titanium dioxide and zinc oxide are used for imparting self cleaning and anti-bacterial properties .The fabric is coated with a thin layer of titanium dioxide particles heaving 20 nanometers diameter. Titanium dioxide is a photocatalyst; when it is illuminated by light of energy higher than its band gap, electrons in TiO₂ will jump from the valence band to the conduction band, and the electron (e) and electric hole (h+) pairs will form on the surface of the photocatalyst. The negative electrons and oxygen will combine to form O2 . radical ions, whereas the positive electric holes and water will generate hydroxyl radicals OH.. Since both products are unstable chemical entities, when the organic compound i.e. dirt, pollutants, and micro organisms falls on the surface of the photocatalyst it will combine with O2 - and OH- and turn into carbon dioxide (CO2) and water (H2O).Since the titanium dioxide acts as a catalyst, so it is never used up. This is how the coating continues breaking down stains over and over. Zinc oxide is also a photocatalyst, and the photocatalysis mechanism is similar to that of titanium dioxide.

PHOTOCATALYTIC SELF CLEANING