Conductivity metallic pigments

If a paint film is to prevent this reaction, it must be impervious to electrons, otherwise the cathodic reaction is merely transferred from the surface of the metal to the surface of the film. Organic polymer films do not contain free electrons, except in the special case of pigmentation with metallic pigments consequently it will be assumed that the conductivity of paint films is entirely ionic. In addition, the films must be impervious to either water or oxygen, so that they prevent either from reaching the surface of the metal. 

Uses. Metallic pigments are used to produce metallic or chrome effects and also as functional pigments (e.g., for corrosion protection, as conductive paints, or for protection against electromagnetic radiation). 

Metallic Pigments. These pigments are metal flakes of various sizes made up of aluminum, copper, zinc, and/or their alloys. The aluminum flakes develop the silver metallic colors, whereas the copper, zinc, and aluminum alloys produce the gold, copper, brass, and bronze colors. The metal effect is modified, not only by shape and size, but also by perticle size distribution within a given product. Since aluminum, in particular, as a fine dry powder, can form explosive mixtures with air, most of these materials are commercially available in paste or liquid concentrates. In addition, surface treatments of these materials enhance their appearance and performance. Flakes of other metals, such as stainless steel, are used for surface protection purposes such as corrosion resistance and electrical conductivity. 

Besides the metal effect pigments there are also metallic pigments and powders for functional coatings like anticorrosion, reflective, heat resistant and conductive coatings. These include zinc, stainless steel and silver pigments. 

Other metallic pigments are coated with inorganic (mostly siUca) or organic (polymer) materials to improve their chemical and thermal stabiUty in waterborne coatings, powder coatings, masterbatches, non-conductive coatings etc. 

It should be noted that metallic pigments can also provide both electrical and thermal conductivity properties to the plastic material involved, hence they can let the system serve as an antenna and microwave absorber, for a number of specific applications. 

Uses Wetting agent, dispersant for precious metals in thick-film deposition on ceramics used in electronics, and in disps. contg. glass frit Features Contributes to conductivity of metal pigments suitable for systems containing petroleum soivs., petroleum oils, oxygenated soivs. improves stabilization of disp. 

In heavy-metal analysis of the same pigments, metals found were present in only trace amounts. The data Hsted place the products tested in the category of nontoxic materials. The Radiant Color Co. has conducted toxicity tests on its own products similar to the A-Series and has found them to be nontoxic. Heavy metals were found only in trace amounts in these tests. 

The reddish metal was already known in prehistoric times. It occasionally occurs as a native metal, but mostly in conspicuous green ores, from which it is extracted relatively easily. It is convenient to work, but not very hard. Not very optimal as a tool ("Otzi the Iceman" had a copper axe with him). Only through the addition of tin is the more useful bronze obtained. Its zinc alloy is the versatile and widely used brass. Copper is one of the coinage metals. Water pipes are commonly made of copper. Its very good thermal and electrical conductivity is commonly exploited (cable ), as well as its durability (roofs, gutters), as the verdigris (basic copper carbonate) protects the metal. Cu phthalocyanines are the most beautiful blue pigments. Seems to be essential to all life as a trace element. In some molluscs, Cu replaces Fe in the heme complex. A 70-kg human contains 72 mg. 

For specialised applications where electrical conductivity is required, such as antistatic flooring or shielding of electromagnetic induction, specific carbon black pigment/filler is used. Copper and nickel metal powders have also been studied (112). A review is available of the electrical properties of polymers filled with different types of conducting particles (416). 

To improve the properties of the raw polymer (wear resistance, creep resistance, thermal and electrical conductivity), various fillers, such as glass fibers, powdered metals, and graphite, are combined with all three types of PTFE polymers, mostly by intimate mixing. Filled fine powders are produced mostly by adding fillers into a dispersion and then coagulating the mixture. Aqueous dispersions can also be modified by the addition of certain fillers, pigments, heat resistant dyes, carbon blacks, and powdered metals, especially when processed into films (see Chapter 6). 

Special applications of bright electro-conductive pigments based on metal-oxide-coated mica are conductive plastic surfaces and antistatic coatings [5.122, 5.148]. 

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