Developing technology and consumers' demand for different features in textiles have contributed to the development of new techniques.
In textiles, in addition to classical coating techniques, Sol-Gel technology, which has been used increasingly in recent years, attracts great attention.
WHAT IS SOL-GEL?
In the sol-gel process, the system transforms from liquid phase (sol) to solid-liquid intermediate phase (gel).
Sol consists of mixing a metal alkoxide as the initiator (precursor) with a solvent (water and/or alcohol) and acidic or basic catalyst at room temperature. It reacts with the -OR group and can be bonded to the fiber surface by covalent bonds over hydrogen.
After the sol solution is applied to the textile surface, it forms the solvent-containing wet gel (lyogel) layer. To form the last layer, this surface is dried and the solvent is removed from the lyogel coating, thus forming a dry gel (xerogel) form.
Hydrolysis and drying conditions in textile coatings significantly affect the density, porosity, and mechanical properties of the coated film.
Sol-gel technology has many advantages. With the sol-gel method, objects with different geometries can be coated homogeneously. Also, it is possible to make a multi-layer coating with this method, as well as pure and homogeneous thin films that can be prepared at low temperatures.
The chemicals used in the coating may be different. If there is no problem with chemicals, the sol-gel method is safe and does not cause pollution. However, it can be harmful to health, depending on the chemicals used. At the same time, the cost of the chemicals used can be high.
The Most Preferred Compounds While Achieving Functional Properties
- Water, oil, and dirt repellency: TiO2, MgO, ZrO, ZnO
- UV protection: TiO2, ZnO, SiO2, Al2O3
- Antimicrobial: Ag ions, TiO2, ZnO
- Antistatic and conductivity: Cu, Polyaniline
- Self-cleaning feature: SiO2, TiO2
- Flammability: Formic acid, Guandine phosphate
Sol-Gel Coating Methods
There are many types of coating with the sol-gel method. These coating methods are dip, spin, spray, electrophoresis, thermophoresis, mixed, and place coating methods.
Dip, spin, and spraying coating methods are commonly used sol-gel coating processes.
Dip Method
It is one of the most important methods of sol-gel coating. It is based on the principle of immersing the solely prepared litter at a certain speed and removing it at the same speed.
The dip coating method takes place in five stages: immersion, draw-up, coating, percolation, and evaporation.
Spin Method
This method is based on the principle that the carrier is rotated horizontally around an axis and the left is dropped on it and the left is spread on the carrier surface by the effect of the centrifugal force.
Spraying Method
It is based on the principle of spraying the material on the base with the help of a spray gun. The number of holes in the tip of the spray gun, the diameter of the holes, the speed of spraying the solution, the spraying distance are important factors that determine the quality of the coating. It is suitable for mass production.
REFERENCES
Özler, F. B., Titanyum ve Alaşımlarının Sol-Jel Daldırma Yöntemiyle Yüzey Modifikasyonu, Yüksek Lisans Tezi, İstanbul Teknik Üniversitesi, İstanbul, 2007
Eryaman, Y., Korkmaz, Y., Süperhidrofob Tekstil Yüzeylerin Florsuz Bileşikler Kullanılarak Sol-Jel Yöntemi ile Modifikasyonu, Derleme Makale, Kahramanmaraş Sütçü İmam Üniversitesi, Kahramanmaraş, 2016