INFLUENCE OF MOISTURE UPON INSULATORS 



237 



cussion, let us classify the commercial fibers into two main groups: 

 (1) the animal fibers, and (2) the vegetable fibers, and a subgroup 

 (2a), the cellulose ester fibers of which the so-called cellulose acetate 

 silk is the sole representative of commercial importance at present. 

 It will be seen by reference to Fig. 1 that over the entire range of 

 relative humidity the animal fibers, silk and wool, absorb more water 



0.2 



0.4 0.6 0.8 1.0 1.2 



LOGio MOISTURE CONTENT — PER CENT 



Fig. 4 — Insulation resistance as a function of moisture content of textiles 



1. Wool yarn 



2. Silk threads purified [sample 1 (o); sample 2 (•)] 



3. Silk threads impure 



4. Cotton threads (o); cellulose acetate threads (+) 



than the natural vegetable fibers. This is true whether we deal with 

 fibers in their natural impure state or after a washing process which 

 has been shown to improve greatly the electrical characteristics of 

 both types of natural fibers. Cellulose acetate absorbs less water at 

 any given humidity than either class of natural materials. 



We have seen that for any given kind of fiber there is an orderly 

 dependence of electrical properties upon the moisture content of the 



