Flake pigments

In principle, all lamellar minerals may be used as barrier pigments, e.g., micaceous iron oxide [5.167]-[5.169], layer silicates (mica), linear polymeric silicates (wollas-tonite), and talc [5.170], However, untreated mica and talc are not very suitable because they are highly permeable to water [5.57]. The surface can be modified with, for example, silanes or titanates, to reduce water permeability and improve adhesion 

Micaceous iron oxide [1317-60-8] Fe203 (specular hematite) 4.6-48 dark gray 

Talc [14807-96-6] Mg3Si4P10(OH)2 2.6-2.8 white, light green to brown 

Flake aluminum pigments with varying platelet thicknesses and shapes are used for corrosion protection [5.175]. For standard specifications, see Table 1 ( Aluminum pastes and pigments ). They are coated with a water-repellent, fatty film and are therefore particularly suitable for conventional solventbome coating systems. They have outstandingly good weather resistance [5.175]—[5.177]. 

Flake zinc pigments have a barrier effect and also act by a cathodic anticorrosive mechanism. Compared with zinc dust coatings, flake zinc pigments are formulated with lower pigment volume concentrations [5.178]. 

---

Pigments for finishes are selected on the basis of their colour, but special attention must be paid to inertness in the chosen binder and stability and light fastness under the conditions of application and exposure. Flake pigments such as aluminium and micaceous iron oxide give finishes of lower moisture-vapour permeability than conventional pigments, and consequently contribute to better protection. 

Crosslinked acrylic microgels in aqueous and non-aqueous media were patented as paint constituents in 1979 to improve the orientation of aluminum flake pigments, restrict the flow of the liquid coating on the substrate and restrict sagging [324]. As the patent speaks of emulsions, insolubility of the microgels and particle sizes up to 200 nm, it is questionable whether these polymers consisted of microgels only. 

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. 

It may be seen from this table that of the A1 flake pigmented... 

Figure 68. Schematic representation of the physical anticorrosion effects of flake pigments...

Copper-zinc alloys with a higher zinc content (brass) cannot be ground or formed into flake pigments on account of their brittleness. Controlled oxidation of natural bronze powders converts them into fired bronze powders. These shades (e.g., English green, lemon, ducat gold, fire red) are produced as a result of interference effects that depend on the thickness of the oxide coating. 

Fig. 5.23 Color variation vs. viewing angle of a Si02 flake pigment with a very thin metal oxide layer.

The SEM micrograph in Figure 5.25 shows a cross section through a Ti02 silica flake pigment. It shows clearly that both the Si02 flake and the Ti02 layer thickness are precisely controlled. 

A CVD-process is known to produce iron-oxide-coated aluminum flakes which form high brilliance colored aluminum pigments with highly interesting interference effects [5.174]. Some of the very new optically variable pigments consist of multilayer flake pigments with a metallic core to obtain metaUic reflection and coverage ]5.175]. 

Epoxy primers cured with amine adducts, containing leafing aluminum flake pigmentation... 

CAS 7439-92-1 EINECS/ELINCS 231-100-4 Synonyms Cl 77575 Lead flake Pigment metal 4 Classification Metallic element Empxical Pb... 

Aluminum paste n. Metallic aluminum flake pigment in paste form, consisting of aluminum, solvent, and various additives. The metallic aluminum pigment can be in the form of very small, coated leaves or amorphous powder, known under the respective designations of leafing and non-leafing . See leafing. 

Cell Flake, Pigment flakes, Eckart America LP Cellu-Cushion, High-density polyethylene foam. Sealed Air Corp. 

Other materials coated in this manner were clays, asbestos fibers, aluminum flake pigment, iron powder, and a titanium dioxide pigment which showed tenfold improvement in photodurability in an organic polymer. By using mordants, the individual fibers in cotton and nylon fabrics were coated with silica which amounted to over 5% by weight. 

Figure 7-7 shows a cross-sectional diagram of metal oxide coated on mica and metal oxide deposited on silica flake pigments. The new properties available with silica flake pigments can be summarized as follows. 

---