Antistatic and conductive additives

Conductive additives such as high-purity carbon blacks are commonly added to compounds where there is a potential hazard from electrostatic discharge. There is also extensive development of systems based on metal fibres, to give higher protection or shielding against electromechanical interference. 

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Markarian J. New developments in antistatic and conductive additives. Plastics Addit Compound [trade journal—Elsevier Ltd.] September/October 2008. 

A simple and convenient method of polymer modification is to introduce an additive. This method is most effectively utilized in the modification of nylon fibers. For antistatic and conductive properties, hygroscopic polymeric materials and conductive materials such as carbon and metal powders are incorporated, respectively. For flame retardant properties, antimony trioxide is added. To impart ultraviolet shielding properties, ultraviolet absorbents are included and inoiganic particles of metal such as silver and zeolite containing metal ions are used for antibacterial and odor preventing properties. 

Antistatic and conductive nylon fibers with improved performance and durability can be prepared by spinning. Since most of conductive additives are inoiganic particles, conductive fibers are generally obtained by composite spinning. However, antistatic nylon fibers are laigely produced by blend spinning because lots of antistatic additives are organic materials. 

Carbon black filled antistatic and conducting composites usually contain 10-30 wt.% filler. (Addition of 1-2 wt.% carbon black for improving the weatherability essentially does not change the conductivity, although it somewhat increases the dielectric loss). The addition of conducting carbon black to thermoplastics increases not only the electrical conductivity, but also the modulus, tensile strength, hardness, melt viscosity and the heat distortion temperature of the compound. It reduces, however, the elongation to break and impact properties. 

Conductive fillers, intrinsically conductive polymers, and organic additives are used as antistatics. There is no common product available which has a combination of the above. The only known combinations are particulate and fibrous conductive fillers, which are claimed to produce a better effect. 

This discussion will focus on chemical antistats and excludes inorganic conductive additives such as carbon black, metal-coated carbon fiber, and stainless steel wire. Chemical antistatic additives can be categorized by their method of application (external and internal) and their chemistry. Most antistats are hydroscopic materials and function primarily by attracting water to the surface. This process allows the charge to dissipate rapidly. Therefore, the ambient humidity level plays a vital role in this mechanism. With an increase in humidity, the surface conductivity of the treated pol5uner is increased, resulting in a... 

High-resistivity materials such as certain plastics are specifically susceptible to the generation of ESD. This problematic property of certain plastics is often improved by incorporating certain conductive additives and fillers called antistats to the plastic to reduce the resistivity of the plastic material. 

Antistatic additives are capable of modifying properties of plastics in such a way that they become antistatic, become conductive, and/or improve electromagnetic interference shielding (EMI). Carbon fibers, conductive carbon powders, and other electrically conductive materials are used for this purpose. 

Antistats such as polyoxyethylenes (151,152) and A/-alkyl polycarbonamide (153) are added to nylon to reduce static charge and improve moisture transport and soil release in fabrics. These additives also alter the luster of fiber spun from bright polymer. Static reduction in carpets is achieved primarily by the use of fibers modified with conductive carbon black (see Antistatic agents Carbon, carbon black). 

Surface-active agents iacrease the conductivity of oils quite significantly (97), and addition of water, probably dissolved at the iaterface with the surfactant, further iacreases the conductivity. Nonionic and cationic surface-active agents are preferred to anionic surface-active agents probably because of their higher solubiHty ia oils and higher hygroscopicity. Many anionic surfactants have adequate antistatic efficiency, but they are used less frequendy. 

Mixing cellulose esters in nonpolar hydrocarbons, such as toluene or xylene, may result in static electricity buildup that can cause a flash fire or explosion. When adding cellulose esters to any flammable Hquid, an inert gas atmosphere should be maintained within the vessel (132). This risk may be reduced by the use of conductive solvents in combination with the hydrocarbon or by use of an antistatic additive. Protective clothing and devices should be provided. 

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