Carbon black pigments physical properties

The physical properties of LSR are similar to the general purpose or medium high-strength peroxide cured elastomers. Other features such as oil and chemical resistance and electrical properties also follow the expected trend for silicone products. The LSR cure system generally results in the cured product being self-extinguishing, and with the inclusion of certain carbon black pigments will easily meet the requirements of the US Underwriters Laboratory flame test UL-94, with a class of V-O. 

Black Pigments. The only black pigment used to an appreciable extent in inks is carbon black It is used in newsprinting, pubHcation, commercial and packaging printing therefore, in large quantities. Black pigments ate offered in fluffy or beaded forms and in a variety of particle sizes and physical properties. 

Adsorption Properties. Due to their large specific surface areas, carbon blacks have a remarkable adsorption capacity for water, solvents, binders, and polymers, depending on their surface chemistry. Adsorption capacity increases with a higher specific surface area and porosity. Chemical and physical adsorption not only determine wettability and dispersibility to a great extent, but are also most important factors in the use of carbon blacks as fillers in rubber as well as in their use as pigments. Carbon blacks with high specific surface areas can adsorb up to 20 wt% of water when exposed to humid air. In some cases, the adsorption of stabilizers or accelerators can pose a problem in polymer systems. 

Fillers are added to the elastomer in order to add bulk, lower cost and/or to improve physical properties such as hardness, strength and abrasion resistance. Typical fillers are materials such as carbon black, talc, china clay and whiting. Carbon black has been shown to contain polynuclear aromatics (PNAs) and there is concern regarding their carcinogenicity (Lee and Hites, 1976). However, despite extra controls there has been a move away from the use of carbon black as a filler in applications involving the primary packaging of parenterals. Its use continues as a pigment or colourant in rubber formulations but at substantially lower levels than that as a filler. 

Pigmental concrete and mortar will normally have the same physical properties as the unpigmented mix except that certain pigments, e.g., carbon black, may cause slight loss of compressive strength at early ages. Carbon can also diminish the effectiveness of air-entraining admixtures. 

Rubber compounds very often contain smaU-particle fillers such as carbon black and silica, to improve processability and physical properties, and to reduce material costs. The most common filler is carbon black, use of which as a pigment dates to ca. 4000 BC. Methods to incorporate fillers, and the effect of their distribution and dispersion on properties, are central considerations, with... 

Pigments are added to give a plastic color, but fliey may also affect the physical properties. Extenders are usually cheap materials added to reduce the cost of a plastic resin. Dyes are colorants chemically different than pigments. Mica is a special pigment added to impact sparkle or metallic appearance. Titanium dioxide (Ti02) and carbon black are two important pigments that merit further discussion. 

Carbon blacks are the most used among all pigments. They have a high pigmentation power and they improve many of the physical properties of polymers, such as light stability, processibility, and mechanical properties. Channel black has been banned in the United States since 1976 only all gas-fired channel black is still permissible in food contact applications. Other carbon blacks, mainly thermal and lamp carbon blacks, are used in rubber reinforcement acetylene carbon black is interesting for its electrical conductivity and is used as an antistatic agent. Activated carbon is also used in some cases. 

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