The Effect of Draw Ratio and Temperature on Electrical Conduction in Nylon Filaments

Abstract

In a study of electrical conduction in nylon as a function of draw ratio and temperature, it was found that the conductance depends upon washing history. Accordingly, a standard washing procedure was devised to allow reproducible and comparable measurements to be made. The conductivity at 30°C thus measured was shown to decrease with increasing draw ratio to an extent greater than can be accounted for by the decreased moisture regain produced by drawing. Upon decreasing the temperature from 45°C to 15°C, the conductivities at constant regain of both drawn and undrawn nylon fell, the difference between the two diminishing and apparently disappearing at 15°C. At none of the temperatures and regains studied could the temperature dependence be accounted for as a simple rate process.. A PREVIOUS PAPER [4] described apparatus and techniques for measuring the electrical resistance of fibers. In that work laws were established for the variation of resistance with length, cross-sectional area, and moisture content of several fibers. The present paper extends the study of fiber resistance to include variation with temperature and structure, the variables whose effects are most likely to shed light on the mechanism of conduction. The work has been carried out with 6,6-nylon, in view of its controlled composition and regular cross section, the existence of extensive collateral information on regain and density, and the availability of special samples drawn from the same melt to six different extensions.Effect of Washing E ff ect of Washing on Conductivity . When dealing with conduction in high-resistance materials, it is essential to specify the treatment used to remove possible contaminating substances. In the work reported by Hersh and Montgomery [4], the fibers were washed for three periods of 3 min. each in changes of distilled water at room temperature. Ordinarily the first washing resulted in a large fall in conductivity, and the two additional washings sufficed for attainment of an apparent terminal value.In the present work, in which bundles of 3,400 nylon fibers in parallel were used, it was observed that the conductivity fell after washing at room temperature for periods up to 24 hrs., but the value rose slowly as the fibers remained in the test chamber to condition at constant humidity. The rate of rise could be accelerated markedly by keeping the fibers in a saturated atmosphere outside the test chamber. In another experiment wherein the fibers were soaked for 3 hrs. in water at 50 ° C and then conditioned back to the test conditions of 62% R.H. and 30 ° C, the conductivity decreased by a factor of 10 or more, but rose again when the fibers were left at fixed conditions. To verify that this was not a spurious instrumental effect, four fiber samples each of draw ratios 1, 2, and 3 were treated as follows: two samples were subjected to the washing and conditioning cycle, and two were kept in the chamber as controls. Figure 1 shows that for fibers of draw ratio 3, conditioning brings the conductances...

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