Sol-gel technique may be described as: “Formation of an oxide network through hydrolysis and polycondensation reactions of a precursor“.
It involves a colloidal suspension of tiny particles in a liquid medium which undergoes a process (hydrolysis and condensation) to form a “gel”.
In the sol-gel process, monomeric alkoxide precursors (M(OR)n which M = Al, Si, Ti, Zr, Ti, etc.; and R = CxH(2x+1) are transformed into an oxide network at two different steps:
– Hydrolysis for substitution of the alkoxide functional groups with the hydroxyl groups;
– Condensation leading to the production of an inorganic network due to the formation of M-O-M chemical bonds.
When the gel is applied as a coating and dried, a hard, glass-like film is created, with a ceramic nature.
The sol-gel technology can be used to realize coatings or surface modifications using precursors containing:
hydrophobic groups (e.g. alkyl or fluoroalkyl);
hydrophilic groups (e.g. PEG or COOH);
functional groups (e.g. –OH, -COOH, -NH2).
Various molecules, nanoparticles or oligomers can be simultaneously introduced in a controlled way into the matrix, opening the door to several properties for the surfaces, such as sensing, antibacterial, flame retardancy, wear resistance, water repellency, ….
This technique can be applied to any surface and provides a well-organized, compact and robust inorganic or hybrid matrix.
Advantages of the sol-gel method:
Versatile: possibility of incorporating nanoparticles and organic materials into coatings;
Extended composition ranges: it allows the production of new hybrid organic-inorganic materials, which do not exist naturally;
Equipment already used in the companies: No need for special or expensive equipment.
This technique can be applied to almost any surface and allows the grafting of well-controlled, compact and robust inorganic or hybrid coatings. The coated material has specific properties, without altering its own inherent properties (e.g transparency, stiffness, flexibility, etc.).
This breakthrough technology pushes the boundaries of knowledge and innovation in the field of surface modification and opens up exciting new perspectives for high-end applications in different sectors such as technical textiles, wearable sensors, medical devices, etc.
Application equipment:
Sol-gel coatings can be applied using conventional industrial equipment (e.g. spray, dip-coating, impregnation, exhaustion). The treated materials can be dried at 80-90°C and, then, cured at 160-170°C.
