Development of static charges

Dryer softeners are employed primarily in North America to control the buildup of static charge in the tumble clothes dryer. The product consists of a 1" x 12" sheet made of polyester and a mixture of a cationic surfactant and a release or distribution agent is applied to the sheet [52-54]. The level of the agent is typically 1.0-2.0g per sheet and is in a solid form on the sheet [55, 56]. The sheet is tossed into the dryer with the wet clothes at the beginning of the cycle and controls the development of static charge throughout the dryer cycle. 

Some solids may develop static charges, making them very difficult to handle without blowing the solid around. Antistatic weighing boats, antistatic brushes, and other procedures for weighing are available to prevent and minimize this problem. The development of static charge can be particularly prevalent inside glove boxes with dry, inert atmospheres. 

Textile finishing encompasses a broad range of approaches and may be directed toward needed properties such as shrinkage control or smooth-dry performance or toward developing properties for specific end uses such as flame retardance, soil release, smolder resistance, weather resistance, or control of static charges. 

In winter, cold air brought into a building and heated to normal room temperature is extremely dry, often less than 5-10 percent relative humidity. When processing solid materials that can develop a static charge, this air should be humidified to reduce static hazards as well as improve the comfort of personnel. 

Some fabrics contain a small percentage of conductive fibers or staple, which limit charge accumulation by air ionization. These fabrics do not depend upon conduction of static charges and may not appear conductive in the electrical resistivity or the charge-decay test. Antistatic performance is not humidity-dependent. Work is under way to develop a standard test for these fabrics (Nelson, Rogers, and Gilmartin, Antistatic Mechanisms Associated with FIBC Fabrics Containing Conductive Fibers, J. Electrostatics 30, pp. 135-148, 1993). 

Moisture Content, Resistance, and Static Charge. The moisture content of human hair probably provides a larger influence on static charge than any other variable, and its direct action is on the electrical resistance (conductance) of hair (i.e., increasing moisture in hair decreases its electrical resistance) [142] therefore, increasing moisture increases the conductivity of the fiber surface so that it is less prone to develop a static charge. 

Antistatic Finishes Owing to its hydrophobicity, polyester builds up static charge readily. Finishes have been developed for polyester that increase the hydrophilicity and ionic character of the fiber and permit more ready dissipation of static charge from the fiber surface. These treatments include lauryl phosphate, morpholine, various polyethylene glycols, organosilicones, and polyamine resins. 

The contact-induced charge separation does not directly involve relative motion of the two contact materials. However, motion certainly can enhance the formation of static charges. In many cases, robbing two polymer fibers produce temperature gradients. Hot spots often develop due to the friction effect, and charges can move from hot spot to cold surrounding area. 

An fuel-air mixture explosion can be initiated by a sudden discharge of static electricity. Yet, while flowing in systems, a fluid develops an electrical charge which will take as long to dissipate as the fluid is a poor conductor. The natural electrical conductivity of jet fuel is very low, on the order of a few picosiemens per meter, and it decreases further at low temperature. 

Electrical Behavior. The resistivity of acetate varies significantly with humidity with typical values ranging from 10 ohm-cm at 45% rh to 10 ohm-cm at 95% rh (16). Because of the high resistivity both acetate and triacetate yams readily develop static charges and an antistatic finish is usually apphed to aid in fiber processing. Both yams have also been used for electrical insulation after lubricants and other finishing agents are removed. 

To prevent contamination, the tanks will be lined with epoxy, except for the bottom and the lower 2 ft of the sides. The lower portions will be lined with an inorganic zinc silicate such as Dimetcote to prevent rust formation and to allow static charges that may develop in the liquid to drain off through the tank.23... 

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