Particles opacity Carbon

Colouring Decoration, protection Add colour and opacity Carbon particles,... 

For preparing lakes, a solution of aluminium sulfate (or chloride) is mixed with sodium carbonate, forming fresh alumina Al(OH)3. The colorant is then added and adsorbed on the surface of alumina. Usually the content of colorant in the lake ranges from 10 to 40%." The product is filtered, washed with water, dried, and milled. The product is allowed to contain unreacted alumina but must not contain more than 0.5% HCl-insoluble matter and not more than 0.2 % ether-extractable matter. - Lakes are insoluble in most solvents used for pure dyes, and they have high opacity and better stability to light and heat. Lakes impart their color by dispersion of solid particles in the food. The coloring properties of lakes depend on particles, crystal structures, concentrations of dye, etc. 

Black pigments. Carbon blacks are organic pigments produced by partial combustion of petroleum products or natural gas. The particle size and intensity of blackness depends on the process and the raw materials used. For example, carbon black pigment prepared from vegetable oils or coal-tar distillates are inferior in color and opacity compared with the high carbon blacks prepared from the petroleum products or natural gas. 

The RI of the medium in which the pigment is dispersed ranges from 1.33 (for water) to 1.4-1.6 (for most film formers). Thus, rutile will give the highest opacity, whereas talc and calcium carbonate will be transparent in fully bound surface coatings. Another important fact that affects light scattering is the particle size hence, in order to obtain the maximum opacity from rutile an optimum particle... 

Fillers must be free of sulfur-containing impurities, iron, and zinc. In order to minimize reduction in clarity, fillers should have a fine particle size and an index of refraction close to that of the PVC resin. If opacity is desired, however, high refractive index fillers such as talc or calcium carbonate can be used to minimize the amounts of the more expensive titanium dioxide opacifying pigment required. 

Fillers may be divided into particulate and fibrous types. Particulates include calcium carbonate, china clay, talc and barium sulphate. Fillers affect shrinkage on moulding and the dimensional stability of the finished plastic, increase tensile strength and hardness, enhance electrical insulation properties and reduce tackiness. They also impart opacity and colour (Figure 3.16). Carbon black is now the most widely used filler for polymers usually in the form of furnace carbon black, which has a particle diameter of 0.08 mm. Fibrous fillers reinforce polymers and greatly increase their tensile strengths. They include fibres of glass, textile and carbon. Plastics filled with fibrous fillers are known as composites. 

Black Silk - for polyethylene film in technically demanding applications calling for superior dispersion, dilution at high additions, and down-gauging with good opacity and UV protection. For best UV protection, it contains carbon black of 20-25 nm particle size at 40% content, and ingredients meeting European food contact requirements. 

Calcium Carbonate. Calcium carbonate (CaCOs) is also known as whiting, limestone, marble, chalk, or calcite. It has been ground and added to rubber compounds to reduce cost and to impart hardness and opacity to rubber articles. Particle sizes range from 2 to 80 /xm for dry-ground product and from 0.5 to 11 /xm for wet-ground product. The chemical composition and crystalline nature depend on the limestone deposit that is mined, for example chalk or marble, and the color of the deposit. 

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