Metal flakes

Metal flakes in a suspension are common. For example, aluminum paint is actually aluminum flakes suspended in paint. Upon application, the flakes orient themselves parallel to the surface and give very good coverage. Similarly, silver flakes can be applied to give good electrical conductivity. 

The fact that plastics are good insulators does not mean that plastics are inert in an electrical field. They can in fact conduct electricity using certain plastics but more so by the addition of fillers such as carbon black and metallic flake (Fig. 4-4). The type and... 

Oxidized metal flakes and metal dust Annealing, deburring, and cutting Shipped to special landfill 30,000 15,810... 

Interference patterns with the reflective and refractive light occurs that varies with the viewing angle. Thin metallic flakes of, for example, aluminium, copper, bronze, coated with a dye are used extensively in automobile wheel hub-caps, and "metallised" car-body paint finishes. 

Other NAD microspheres are composed of styrene, MMA, hydroxyethyl acrylate, acrylic acid and acrylonitrile and are blended with acrylic copolymers and melamine/formaldehyde resins [341,342]. Particles of this polymer are used as rheology modifiers to prevent sagging in automotive coatings and for controlling the orientation of metal flake pigments. 

Attractive metallic effects can be obtained by incorporating very thin, small flakes of aluminium, copper or copper/zinc alloys in otherwise transparent surface coatings. The metal flakes act as tiny mirrors within these paints, which are particularly effective on the curved surfaces of cars since the colour changes with the angle from which the surface is viewed. The orientation of the flakes within the paint film also changes the colour seen by the eye, so that careful dispersion of the metal components of the paint is essential. 

Liu, N.-I. and van der Meer, R Synergistic effect of metal flake and metal or metal coated fiber on EMI shielding effectiveness of thermoplastics, US Patent 4 566 990, 1986, and references therein. 

Although pyrophoric metals can come in various shapes (spherical, porous spheres or flakes), the calculation to be shown will be based on spherical particles. Since it is the surface area to volume ratio that determines the critical condition, then it would be obvious for a metal flake (which would be pyrophoric) to have a smaller mass than a sphere of the same metal. Due to surface temperature, however, pyrophoric flakes will become spheres as the metal melts. 

Conductive composites are obtained when powered metal fillers, metal flakes, or metal-plated fillers are added to resins. These composites have been used to produce forming tools for the aircraft industry and to overcome electromagnetic interference in office machines. 

A novel application for the metal flake based materials is in security outlets because they are non-photocopyable. Pigments from Flex Products have been used by SIPCA to produce optically variable green-to-black inks for printing secure images on US dollar bills. ... 

The coefficient of linear expansion of unfilled polymers is approximately 10 X 10 5 cm/cm K. These values are reduced by the presence of fillers or reinforcements. The thermal conductivity of the polymers is about 5 X 10 4 cal/sec cm K. These values are increased by the incorporation of metal flake fillers. The specific heat is about 0.4 cal/g K, and these values are slightly lower for crystalline polymers than for amorphous polymers. 

Metal effect pigments (Fig. 71 B) consist of small metallic flakes (mainly aluminum or Cu/Zn bronze) which act as small mirrors that reflect almost all of the incident light. 

Reduction of suitable aqueous metal salts by electroless plating yields metal-coated mica pigments. They are less expensive than noble metal flakes (Au, Ag) and their brilliant metallic appearance is comparable with that of metallic flakes [5.192], [5.193],... 

The metal effect depends not only on particle size and particle size distribution, but also on the orientation of the metal flakes within the coating film, particle shape, the transparency of the binder matrix, and the presence of colored pigments or dyes. 

Summary Electroplating is carried out by utilizing identical electrolysis techniques as seen in methods 1 and 2, but instead of forming metal flakes or crystals, the cathode is composed of a desired metal object to be plated. To plate metal objects, the metal object is placed as the cathode, and a solution of either dilute hydrochloric acid and corresponding metal anode, or a solution of a water soluble metal salt utilizing a metal anode or inert anode, is electrolyzed using varying current to plate the desired metal object. The electrolysis process is rapid and can be carried out with success in minimal amounts of time. 

Figure 37 Scanning electron micrograph of metal flake paint for trucks showing entrained dirt and intentionally added metal flakes. The particulate material in this micrograph averages several micrometers in diameter.

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. 

The film is continuously coated from the front or backside by rolls or knife coating. For small-volume items frequently gravure or a roller coater is used. All these applications result in an even orientation of the metallic flakes parallel to surface. The frequently used spraying technique has a disadvantage in this case because, due to its high viscosity, the metal pigment shows only little orientation. 

Effect Pigments Formed by Coating of Metal Flakes... 

The aluminum flakes can be coated with aluminum oxide and/or silicon dioxide in the liquid phase before the CVD process to reduce the reactivity of the metal and to create multilayer color effects. These pigments show strong angle-dependent coloristic effects (color travel) [5.158]. Metal halogenides are difficult to use as gas-phase precursors for metal oxide coating because of the reactivity of the metal flakes and the corrosion of steel in chloride atmospheres. The use of TiCU and water vapor was described about ten years ago. However, no commercial products have, as yet, been introduced. 

Mica flakes can also be coated in CVD processes using the same technique as discussed for metal flakes. In addition, one can also use metal chlorides as precursors for oxide coating on mica. However, essentially the same products can be obtained more easily by precipitating the oxides from the liquid phase. 

The anisotropic shape of the metallic flakes should be considered during dispersion and application of these pigments high shear forces may damage the pigments and the effect and should therefore be avoided. 

In the so-called bonding-process , the metallic flakes are thermally and mechanically bonded to the surface of the resin powder, avoiding separation in the overspray and thereby giving problem-free reuse of the material. Furthermore there are optical advantages in bonded metallic powder coatings due to the very homogeneous distribution of the metallic flakes. 

Placer— An accumulation of metallic flakes or nuggets, typically gold, in sand and gravel deposited by running water. 

Lacquer was probably first used solely as a protective coating decorative elements have evolved with time. Objects may be simply colored in monochromatic red or black, for example, Chinese bowls and carved boxes. Other objects may be highly ornate, with patterns introduced by using metal flakes or foil to produce decorations on the interior subsurface layers. Some pieces may have designs of inlaid mother of pearl still others have a combination of metal-flake patterns and mother-of-pearl inlay. It is common for some objects to have 60-100 individual layers. Hardening and polishing each layer takes from several days to months it might require many years for completion of an article. 

In order to check the paintability of parts molded with Q2-7119, test panels molded with and without silicone fluid were post-cured, solvent wiped with toluene, primed with PPG Durethane 600 Primer and then top coated with Durethane 300 blue metallic flake or white. Painted samples were exposed for 2 years in Florida Direct Black Box 5° South and then evaluated for appearance and adhesion. Results of these tests showed no difference between control and IMR-containing panels. Paint adhesion was excellent. 

Novamet developed a concept to improve the properties of nickel flakes by coating them with 15% silver. The coated flakes have both conductivity and ferromagnetic properties. In addition, because of the differences in density (Ag -10.5 andNi- 8.9 g/cm ), it is possible to save 15% in material since conductivity is related to volume rather than to weight and surface conductivity is usually of primary importance. Figure 2.39 shows the morphology of several conductive materials. Metal flakes from silver coated nickel and copper flakes have irregular shapes because they are formed from spherical particles which were first coated with silver and then flattened by mechanical forces. The apparent difference in... 

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