Present view of static charges in textiles textiles static charges is a variety of mechanisms may cause
charge transfer to occur at surfaces in contact. Consequently, large charges
will form on the surfaces, but these will leak away through the air, the
material, or surface-dressings, and observed charges are much smaller. Leakage
through the air occurs until the field near the charged surface is reduced to a
value which the air can support. If the ratio of the conductance of the
material to the speed of separation is high enough, current will flow the
material and further reduce the charge.The leakage will take place from the
material just beyond the point of separation, either across the gap to the
other surface or to points on the material behind the point of separation. If other
conductors are present in the neighbourhood, some current may flow to them.
The limiting condition for high
static charges, and hence the susceptibility to troubles in use, has been shown
to depend on the resistance of the material: low-resistance materials, such as
cotton and viscose rayon will rarely give static troubles; higher-resistance
materials like wool, silk, and acetate will give trouble more often; and very
high-resistance synthetic fibers will give most trouble. The speed of the
process is also important: thus, to avoid fog-marking in weaving, dissipation
in 10 minute, needing a total current of o.003 microamps is adequate, but to
avoid trouble in carding, dissipation must take place in 0.1 second, needing
0.07 microamps; to avoid trouble in warping, it must take place in 0.01 second,
needing 5 microamps.
Methods of getting rid of static
charges depend upon increasing the leakage- by lowering the resistance either
of the material, or of the air, or by providing a conducting liquid at the separation.
The resistance of the material may be lowered by raising the humidity or by
moistening it. The resistance of the air may be lowered by ionizing it, either
by using a high-voltage static eliminator or by the presence of a radio-active
material. Safe concentrations of the latter are only sufficient to cause a slow
discharge. The use of electrostatic eliminators in the textile industry has
been described by Henry. The use of anti-static agents is discussed by Sagar
and by Gotze et al. Unfortunately, the
hygroscopic salts which are the most effective anti-static agents are usually
unsuitable for various other reasons.
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