Читать книгу Concise Handbook of Fluorocarbon Gases - Sina Ebnesajjad - Страница 30

Fluoropolymer coatings (also paints or finishes) have also developed based on their stable dispersions obtained by emulsion polymerization. The two coatings with the largest market share are based on polytetrafluoroethylene and polyvinylidene fluoride. One well-known application of these coatings is in non-stick cookware and bake ware. Fluorinated coatings are extensively applied to surfaces in industrial environments to protect them from a variety of corrosive agents [13].

Coatings have the advantage of ease of propagation based on few fluoropolymers by manipulating the formulation. Fluoropolymers can be converted into coatings in two separate ways, as liquids or solids. PTFE must be applied as a liquid coating in contrast to the melt processible fluoropolymers that can also be powder-coated. Fluoropolymer paints are formulated as water-based (aqueous) or solvent-based products. The latter is limited to cases in which aqueous dispersions would not work.

Fluorinated coatings, similar to other paints, are mixtures of a variety of components including liquid carriers, pigments and specific additives in addition to fluoropolymers and additional polymeric binders. Pigments affect the color and appearance of the coatings as well as its functions such as abrasion resistance, thermal conductivity, the extent of porosity and electrical resistance/conductivity. Specific additives are sometimes incorporated to modify the rheology of the paint, wettability of the final coating and facilitate formation of the film at the time of baking. Other polymers are included in the paint to enhance the adhesion of the paint to the substrate or increase its hardness thus overcoming shortcomings of fluoropolymers.

Like other paints those made with fluoropolymers can be applied as one or more “coats” or layers. Flexibility of fluoropolymer content and availability of thickness ranges (2.5-2,000 µm) are two important features of those paints. The base polymers polyvinylidene fluoride and polytetrafluoroethylene provide a broad range of bake temperature ranging from 175 to 440°C. The combination of material properties, coating thickness and process variables determine the performance parameters of the final paint.

Applications of fluorinated paints include chemical process equipment liners, insulating coatings for electronics, non-stick coatings for cookware, surgical patches and glass fiber fabric coatings used for roofing of large structures flue gas heat exchangers, interior of exhaust ductworks and others.