Static charge, polymer electricity

Polymer blends for packaging and materials handling of electrical components would require a degree of electrical conductivity to provide for static charge dissipation. This can be achieved either by a conductive additive, such as carbon black, carbon nano-tubes or metal fibers, or via blending with a conductive polymer like polyanUine. Blending of the latter is necessary to provide flow... 

Synthetic fibres take a static charge because they are non-conductive and only absorb small quantities of water. This effect is reinforced by low air humidity, particularly in winter, and soiling may be increased. Antistatic finishings reduce the high electrical resistance of fibres. These consist of hydrophilic surface active polar compounds (tensids), carbon particles, electrically guiding polymers or salts. Textiles may also be made antistatic by incorporating metallic or metallised fibres or conductive carbon fibres which are coated with polyamide. 

Plastics are mostly electrical insulators. The development of a static charge on two plastic film surfaces during their mutual contact occurs by the transfer of electrons from one film surface to the other during rubbing or rapid separation. It is an undesirable consequence of insufficient conductivity, especially in polymers with a very low tendency to absorb moisture, and static discharges can reach several thousand volts per centimetre. This leads to ... 

In order to conduct electricity, greater or lesser free motion of electrons in the material is required. However, electrical behavior involves questions not only of conduction and resistance but of static charges. Most polymers are insulators, except if they have alternating double and single bonds see Section 14.7.3. The motion of electrons in polymers, and in materials generally, also affects thermal conductivity. Thus good electrical insulation and good thermal insulation (low coefficient of heat transfer) are closely related physically. That is why pots are made out of metal, but pot handles are made out of plastic. Lack of electron-free motion also contributes to transparency in pure, amorphous plastics such as polystyrene and poly(methyl methacrylate). 

Automotive and electrical/electronics industries are the largest markets for engineering polymers which include Crastin PBT polyesters, Hytrel thermoplastic polyester elastomers, Rynite PET, high-temperature Thermx PCT (polycyclohexylene dimethyl terephthalate), Tribon composites and Tynex filaments, Vespel polyimide parts and shapes, Zenite liquid crystal polymers and Zytel PA resins. In July 2005, DuPont launched the DuPont Vespel SP-202 composition whose properties include the prevention of static charge build-up. Other products include Delrin acetal resins, engineering thermoplastic vulcanisates. Minion mineral reinforced PA resins and Teflon PTFE fluoropolymer resins. 

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