Fluoropolymers for Coating Applications

By Barry Jones

Unique characteristics of the fluorine atom result in the interesting properties of polymers that contain them. A fairly small atom, fluorine has very low polarizability and high electronegativity. Because there is a high degree of overlap between the outer orbitals of fluorine and the corresponding orbitals of second pe­riod elements, bonds formed between carbon and fluo­rine are very strong.

The higher bond energy of the C-F bond compared to the C-H bond leads to greater ther­mal stability. Perfluoropolymers, which contain only C-F bonds, have excellent chemical and weather resistance. The small dipole moment of these compounds also con­tributes to their oil and water repellency, as well as their low surface tension, low refractive index, low fric­tion coefficient, and reduced adhesion to surfaces.

Partially fluorinated polymers exhibit a strong elec­tron attracting ability, resulting in a high dielectric con­stant and optical activity. In small molecules, this at­tribute leads to enhanced acidity and lipophilicity and the ability to block metabolic pathways, making fluo­rine-substituted compounds ideal as pharmaceuticals.

Other characteristics of fluoropolymers determined by the strength of the C-F bond and the low polariz­ability and high electronegativity of fluorine include soil resistance, insulating properties, and the ability to act as a gas barrier.