Carbon black pigments conductivity properties

Other important properties of Cr02 when used as a magnetic pigment are its black color, electrical conductivity (2.5-400 O-1 cm-1 [5.27]) and relatively high crystal hardness (Mohs hardness 8-9 [5.20]). Therefore, coating formulations based on Cr02 require less or even no additives such as carbon black (good conductivity, black color) or refractory oxides such as alumina. 

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). 

As discussed in Chapter 10, a wide variety of additives is used in the polymer industry. Stabilizers, waxes, and processing aids reduce degradation of the polymer during processing and use. Dyes and pigments provide the many hues that we observe in synthetic fabrics and molded articles, such as household containers and toys. Functional additives, such as glass fibers, carbon black, and metakaolins can improve dimensional stability, modulus, conductivity, or electrical resistivity of the polymer. Fillers can reduce the cost of the final part by replacing expensive resins with inexpensive materials such as wood flour and calcium carbonate. The additives chosen will depend on the properties desired. 

In addition to its role as a pigment, carbon black may be incorporated into polymers as a reinforcement for elastomers, as a UV stabiHser in polyolefins, or as an electrically conducting additive. In each case the physiochemical properties of the filler and its ultimate state of dispersion is critical in order to achieve... 

Besides their two main uses as reinforcing fillers and pigments, small amounts of carbon blacks are used by the electrical industry to manufacture dry cells, electrodes, and carbon brushes. Special blacks are used to give plastics antistatic or electrical conduction properties. Another application is the UV stabilization of polyolefins [4.31]. 

The aim of this chapter is to provide an understanding of how carbon black particle size and shape translate into dispersion quality and other performance attributes in plastics applications. While this chapter focuses on carbon black s effectiveness as a pigment, some attention will also be paid to some of the other plastics performance properties it influences, such as stability against UV radiation, effects on mechanical properties, and electrical conductivity. At its conclusion, this chapter will help the reader select an appropriate carbon black grade for specific plastics applications. 

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). 

The pigmentation of synthetic fibres with carbon black has been practised for a good number of years. Latterly, its potential for promoting electrical conductivity in fibres has been explored. Nowadays, there is rapidly growing interest too within the textiles community in the incorporation of carbon nanotubes into fibres, particularly as a means of reinforcing them. However, their incorporation at a sufficient level would also render the fibres electrically conducting, and no doubt this property will be fully explored over the coming years. 

Examples of inert or extender fillers include china clay (kaolin), talc, and calcium carbonate. Calcinm carbonate is an important filler, with a particle size of about 1 pm. It is a natural product from sedimentary rocks and is separated into chalk, limestone, and marble. In some cases, the calcium carbonate may be treated to improve interaction with the thermoplastic. Glass spheres are also used as thermoplastic fillers. They may be either solid or hollow, depending on the particular application. Talc is a filler with a lamellar particle shape. It is a namral, hydrated magnesium silicate with good slip properties. Kaolin and mica are also natural materials with lamellar structures. Other fillers include woUastonite, silica, barium sulfate, and metal powders. Carbon black is used as a filler primarily in the rnbber industry, but it also finds application in thermoplastics for conductivity, for UV protection, and as a pigment. Fillers in fiber form are often used in thermoplastics. Types of fibers inclnde cotton, wood flour, fiberglass, and carbon. Table 1.3 shows the fillers and their forms. An overview of some typical fillers and their effect on properties is shown in Table 1.4. Considerable research interest exists for the incorporation of nanoscale fillers into polymers. This aspect will be discussed in later chapters. 

Carbon black can fnnction as a UV stabilizer, thermal antioxidant, extender in crosslinked polyethylene (XLPE) cable compounds, antistat in vinyl records, modifier of polymerization rate in nnsaturated polyesters, conductive filler, and colorant. Although commonly used in rubbers and thermoplastics, carbon black does not improve the properties of thermosetting resins significantly. However, it is often used as a pigment and for obtaining electrical conductivity. 

Properties affected Colour carbon black also has useful anti-static properties, can provide electrical conductivity black pigments also give effective UV screening also used as a reinforcement in rubber compounds (the largest overall use)... 

Carbon blacks are extensively used in rubbers and elastomers, in loading from 10 to 150 phr, and for improvements in stiffness, strength, processability, and abrasion resistance (79). Particle size and concentration are optimized on the basis of balances in mixing-compounding, heat buildup, property improvement, and cost. Carbon black fillers, without considering the electrical conductive blacks, are used in plastics, predominantly as pigment or colorant. 

Additives. Many PSAs contain additives that, imlike tackifiers or plasticizers, are not intended to affect the inherent PSA properties. Pigments, such as titanium dioxide, are added to change a PSA s appearance. Metal particles or carbon black can be added to provide electrical conductivity. Drugs such as nitroglycerin, nicotine, or estradiol are added for use in transdermal drug delivery. 

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. 

Carbon black is widely used as a pigment it also provides self-lubricating properties and increases conductivity (electrical and thermal). 

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