1.2.2 Dielectric properties

1.2.1 Conductive properties

Electromagnetic Materials and Devices

fibers and yarns.

relative humidity:

Table 2.

182

Mass specific resistance of textile materials.

the density of the material in 1 g/cm<sup>3</sup>

where n and K are experimental constants.

resistance and surface specific resistance (Table 2).

area S, and related to material properties. That is,

The electrical conductivity of textile materials is expressed as specific resistance. There are usually three representations: volume specific resistance, mass specific

According to the law of resistance, the resistance R of the conductor is proportional to the length L of the conductor, inversely proportional to the cross-sectional

L

<sup>S</sup> (1)

ρ<sup>m</sup> ¼ d � ρ<sup>V</sup> (2)

lgρ<sup>m</sup> ¼ �nlgM þ lgK (3)

. In actual measurement, the moisture content

. d is

. For most

R ¼ ρ<sup>V</sup> �

where ρ<sup>m</sup> represents the mass specific resistance, and the unit is Ω cm/cm<sup>2</sup>

of the fiber or the relative humidity of the air has a great influence on its electrical resistance. The dried textile fibers have extremely poor electrical conductivity, and

textile materials, there is an approximate relationship between the moisture content M and the mass specific resistance ρ<sup>m</sup> of the textile materials in the range of 30–90%

Type of fiber lg ρ<sup>m</sup> n lg K Cotton 6.8 11.4 16.6 Ramie 7.5 12.3 18.6 Silk 9.8 17.6 26.6 Wool 8.4 15.8 26.2 Washed wool 9.9 14.7 26.6 Viscose fiber 7.0 11.6 19.6 Acetate fiber 11.7 10.6 20.1 Acrylic 8.7 — — Acrylic (degreasing) 14 — — Polyester 8.0 — — Polyester (degreasing) 14 — —

their mass specific resistance is generally bigger than 10<sup>12</sup> Ω cm/cm<sup>2</sup>

where ρ<sup>V</sup> is the resistivity or volume specific resistance and its unit is Ω cm, and it is the physical expression that indicates the electrical conductivity of a material. For textile materials, the cross-sectional area or volume is not easy to measure; so, we usually use the mass specific resistance ρ<sup>m</sup> rather than the volume specific resistance ρ<sup>V</sup> to indicate the conductivity of textile materials, especially for the
