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BELL SYSTEM TECHNICAL JOURNAL 



moist the textile may become, no direct path for the leakage of current 

 is formed as the fibers are separated from one another by two films of 

 cellulose acetate. 



g-<giiifiNftWiw^*yii^*iiW»rj 





■MaMMMMPIMMMtMiiMMP 



riiii'JMiiMiii ii»— »<*»>•— «M»M 



Fig. 1 — Textile insulated wire before and after treatment with cellulose acetate. 



(Enlarged 4 diameters.) 



Development of Process 

 Extrusion of a coating as thin as wanted, about 0.0015 inch, ap- 

 peared to be out of the question. Even if it were possible the coating 

 would not adhere firmly enough to prevent cracking ofT when the wire 

 is twisted or otherwise roughly handled. The study of method was 

 therefore confined to coating the textile insulated wire from a solution. 

 Several solvents for the flake cellulose acetate were considered but 

 acetone was adopted, at least for the time being, as it was known to 

 have the desired characteristics and would simplify the problems in- 

 volved. The solution would have to be low in viscosity to produce 



