Self-cleaning Finishes for Functional and Value …
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surface of the lotus leaves making an uneven micro-texture. Air molecules are thus
easily trapped in interstitial spaces of the rough surface resulting less adherence of
water and dirt molecules by reducing adhesive forces. Water molecules appear like
sphere over such surface and roll over easily and in the course remove the dirt particles
away from the surface [2–9]. Self-cleaning effect can be achieved by textile materials
either by preparing a hydrophobic surface or by some hydrophilic coatings. Both of
these types of surface coatings can help to clean textile surface without laundering.
2 Principles of Preparation of Self-cleaning Textiles
There are two principal methods of preparing self-cleaning textiles. It can be prepared
either by coating of textile surface with super hydrophobic materials (such as silicones, fluorocarbons etc.) or by coating with some functional hydrophilic materials
by the route of nanotechnology.
A liquid droplet can wet a solid surface when the surface tension of a solid is higher
than the surface tension of the liquid. Therefore, the surface tension of the solid need
to be reduced than that of the liquid for achieving liquid repellency. Fluorocarbons
are the carbon compounds which contain perfluorinated carbon chain possessing a
very low surface tension of about 10 dyne/cm. During the application process, the
fluorocarbons form a coat of thin layer around the textile surface. As a result, surface
tension of the coated textiles becomes lower than that of water and water repellency
effect is achieved. A water droplet then does not adhere to the textile surface and rolls
out off. Silicones are actually organosilicon compounds which are highly explored
for preparation of super hydrophobic textile surfaces. There are various approaches
available in literature for preparation of super hydrophobic self-cleaning surfaces
using silicones. PDMS (polydimethylsiloxane) is one of the popular silicone, can be
used for surface modification of textiles by exciting CO 2 pulsed laser to introduce
peroxide groups onto the PDMS surface to create a rough surface. These peroxide
groups assist graft polymerization of 2-hydroxyethylmethacrylate (HEMA) onto the
PDMS. By this method excellent hydrophobic surface achieved with water contact
angle of about 175°. But these hydrophobic coating processes have drawback in
terms of durability of the coat which is not satisfactory and in case of cotton material this is found to be very poor. Other demerit is hazardous effect of the fluorine
compounds which reacts with biological issues and causes skin irritation [1, 3, 10–
14]. Nanotechnology is relatively a new approach of achieving self-cleaning effect
for textiles. This route is proved to be technically viable as well as economically
successful. Various approaches of preparing self-cleaning textiles by this route are
proposed in literature by various researchers. Most widely described approach is by
the applications of photo catalyst like TiO 2. Other methods are using silver nanoparticles, carbon nanotubes, colloidal metal oxide, N halamine, microwaves irradiation,
etc.
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surface of the lotus leaves making an uneven micro-texture. Air molecules are thus
easily trapped in interstitial spaces of the rough surface resulting less adherence of
water and dirt molecules by reducing adhesive forces. Water molecules appear like
sphere over such surface and roll over easily and in the course remove the dirt particles
away from the surface [2–9]. Self-cleaning effect can be achieved by textile materials
either by preparing a hydrophobic surface or by some hydrophilic coatings. Both of
these types of surface coatings can help to clean textile surface without laundering.
2 Principles of Preparation of Self-cleaning Textiles
There are two principal methods of preparing self-cleaning textiles. It can be prepared
either by coating of textile surface with super hydrophobic materials (such as silicones, fluorocarbons etc.) or by coating with some functional hydrophilic materials
by the route of nanotechnology.
A liquid droplet can wet a solid surface when the surface tension of a solid is higher
than the surface tension of the liquid. Therefore, the surface tension of the solid need
to be reduced than that of the liquid for achieving liquid repellency. Fluorocarbons
are the carbon compounds which contain perfluorinated carbon chain possessing a
very low surface tension of about 10 dyne/cm. During the application process, the
fluorocarbons form a coat of thin layer around the textile surface. As a result, surface
tension of the coated textiles becomes lower than that of water and water repellency
effect is achieved. A water droplet then does not adhere to the textile surface and rolls
out off. Silicones are actually organosilicon compounds which are highly explored
for preparation of super hydrophobic textile surfaces. There are various approaches
available in literature for preparation of super hydrophobic self-cleaning surfaces
using silicones. PDMS (polydimethylsiloxane) is one of the popular silicone, can be
used for surface modification of textiles by exciting CO 2 pulsed laser to introduce
peroxide groups onto the PDMS surface to create a rough surface. These peroxide
groups assist graft polymerization of 2-hydroxyethylmethacrylate (HEMA) onto the
PDMS. By this method excellent hydrophobic surface achieved with water contact
angle of about 175°. But these hydrophobic coating processes have drawback in
terms of durability of the coat which is not satisfactory and in case of cotton material this is found to be very poor. Other demerit is hazardous effect of the fluorine
compounds which reacts with biological issues and causes skin irritation [1, 3, 10–
14]. Nanotechnology is relatively a new approach of achieving self-cleaning effect
for textiles. This route is proved to be technically viable as well as economically
successful. Various approaches of preparing self-cleaning textiles by this route are
proposed in literature by various researchers. Most widely described approach is by
the applications of photo catalyst like TiO 2. Other methods are using silver nanoparticles, carbon nanotubes, colloidal metal oxide, N halamine, microwaves irradiation,
etc.