Conductive and Magnetic Fillers

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). 

For magnetic applications, the use of strontium ferrite powder has been characterised (234). The use of barium ferrite has been optimised (362). 

Carbon blacks are made by the combustion of natural gas, or acetylene, or various hydrocarbon oil feedstocks under reducing conditions. In earlier times, channel blacks were made by thermal decomposition of natural gas in an open system with the black being collected on lengths of channel iron in the shape of long inverted vees of angle iron supported over a line of gas flames. 

Increased efficiency and reduced loss to the surroundings are achieved in closed furnace systems yielding furnace black or lampblack. Thermal decomposition of natural gas produces thermal blacks with large primary particles ( 500 nm) and 

Type Surface area by nitrogen adsorption (m /g) DBPA (cmViOOgJ Volatiles %) 

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The incorporation of a variety of semiconducting, conducting, dielectric, and magnetic filler materials (e.g., another CP/ICP, QCNs, nanoparticu-... 

The polymer performance and production efficiency can be enhanced as a function of the basic features of the reinforcement fillers. In the attempt to achieve fillers with increased performance, the following features must be monitored density, flame retardancy, mechanical resistance, thermal conductivity, and magnetic properties. Nanoparticles of carbides, nitrides, and carbonitrides can be used to reinforce polymer matrix nanocomposites with desirable thermal conductivity. However, current trends in the design of these materials reveal that is not enough to choose a wellperforming material for each component of the heat dissipation path. In addition, careful attention must be paid to the manner in which these materials interact with each other. A filler that conducts heat well but does not wet the matrix may lead to poor results compared to a lower conductivity filler that does wet the matrix. In other words, a major fact that leads to interfacial resistance is faulty physical contact between filler and matrix, which primarily depends on surface wettability (Han and Fina2011). 

Extenders can be used to control curing exotherms and moisture permeability, to impart increased strength or to tailor properties such as hardness, heat distortion, thermal expansion coefficients and thermal conductivity. More novel fillers can be used to impart electrical conductivity and magnetic properties or to reduce the compounds density by the incorporation of small hollow glass spheres. The selection of the correct filler is of the utmost importance and all the critical desired properties of the cured compound must be taken into account before a particular filler can be decided upon. 

Depending on the physical properties and size of fillers, the behavior of particle-filled suspensions and filled polymer compounds change. Such properties primarily include particle density, shape, and interaction. To these might be added particle hardness, refractive index, thermal conductivity, electrical conductivity, and magnetic properties. 

Modification of electrical and magnetic properties Conductive, nonconductive, and ferromagnetic metals, carbon fiber, carbon black, and mica Degradabibly Organic fillers starch and cellulosic fibers... 

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