Dissipation of Triboelectric Charge into Air from Textile Surfaces

Abstract

Triboelectric charges on textile fabrics are thought to dissipate mainly by conduction by means of free electron diffusion. Charges on the surface of fabrics disappear by other processes, however, such as neutralization with counter ions and scattering into the air. In this study, water molecules on the textile surface play an important role in the charge scattering into air, i.e., electric charge carried away by water molecules when they evaporate. Two kinds of water molecules exist on the textile surface—one not related to charge dissipation and one carrying the electronic charge away from the fabric surface.Triboelectricity, the static electricity generated on dielectric substances has long been a subject of interest. With the increasing use of polymers and synthetic fibers, many problems and accidents are caused by static electricity.The mechanism of charge separation between two different materials can be clearly explained in the case of metals using their work functions. In the cast of polymeric materials, however, the mechanism is not clearly understood because of complex surface structures, e.g., chemical structure and chain orientation [ 1,7 ] . Also in the case of metals, the generated charges dissipate so rapidly that they are difficult to measure. On a dielectric surface, however, the generated charges remain for a fairly long time as static charges, which lead to bothersome and even hazardous problems.The generation, accumulation, and polarity of static charges produced by rubbing have been studied intensively, with many reports on the triboelectric series [ 2,5,6 ] . Based on these experimental results and considerations, new conductive fibers such as &dquo;epitropic&dquo; fibers [3] ] and many kinds of antistatic fibers have been produced, but the mechanism of generating triboelectric charges remains to be clarified.The dissipation of generated charges has been treated as a rather simple phenomenon, i. e., the charges scatter mainly by conduction [ 12 ] . The decay function for charge dissipation is often observed to be exponential with time. Hence, static dissipation has been estimated by the time required for the chatge to fall to half its original value. The half life of the electrostatic charge is known to depend strongly on fabric surface conditions [ 11 ] . The moisture contents of both ambient air and fabric play important roles in conducting the static charges generated. But dissipation by conduction is not the only mechanism involved in the decay of surface charges. These charges penetrate into the bulk of the fabric and also scatter into the air. In this paper, we . measure the dissipation of electrostatic charges into the air. ExperimentalWhite plain woven fabrics of many kinds, purchases from Kansai Iseikatsu Kenkyu-kai ( Osaka, Japan), were used after eliminating the finishing reagents through water washing with detergent. The sampks were dried with care to prevent structural heterogeneity and to obtain homogeneous, uncreased sampla. Theae sample cloths were cut into strips 7.5 c...

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“…For hydrophobic insulator materials, the way of charge leakage includes electric conduction through the volume of the insulator and electric conduction through the surface of the insulator [27]. For hydrophilic textile materials, the way of charge leakage also includes the process of charge escape (charge escapes into the air through the free water evaporation path) [29,30]. Figure 1 is a schematic diagram of a charge decay model of a charged capacitive (non-contact) textile electrode, where Q 0 is the initial charge amount of the electrode, Q V (t) is the charge decay through volume conduction path, Q S (t) is the charge decay through surface conduction path, Q G (t) is the charge decay through gas ions neutralization path and Q F (t) is the charge decay through FWEP.…”

“…According to the values of the parameter in Table 1, the function curves of Q V (t), Q G (t) and Q F (t) in Equations (2)-(5) are normalized and plotted in Figure 3. Since the rate constant of charge escaping into the air is related to the free water content of the material and the relative humidity of the air, the range of λ measured in the experiment is about [0.07,17.43] in reference [29] and λ is taken as 0.2 and 2, respectively, for the simulation in Figure 3. As shown in Figure 3, the blue solid curve represents the decay of relative surface charge with time for textile electrode through the volume conduction path, the orange dot curve represents the decay of relative surface charge with time on the textile electrode through the gas ions neutralization path.…”

“…As shown in Figure 3, the blue solid curve represents the decay of relative surface charge with time for textile electrode through the volume conduction path, the orange dot curve represents the decay of relative surface charge with time on the textile electrode through the gas ions neutralization path. The black dash-dot curve and the red dash curve represent the decay of relative surface charge with time for a textile electrode through the FWEP when λ is 0.2 and 2, respectively, where 0.2 is the experimental value of polyester fiber at 20 • C, 65% RH and 2 is the experimental value of cotton under high humidity [29]. The time when the charge decays to half of the initial charge is defined as half-life τ 0.5 and labeled in Figure 3.…”

“…When only considering the FWEP, the residual charge on the textile electrode Q′F(t) can be expressed by Equation 5, where λ is the rate constant of the charge escaping into the air and is related to the free water content of the material (textile electrode) and the relative humidity (RH) of the air [29]. As shown in Figure 3, assuming no corona discharge, the half-life of charge decay through the gas ion neutralization path is theoretically very long.…”

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