PARAGUTTA, A NEW INSULATING MATERIAL 135 



constituent is the same hydrocarbon which gutta percha contains. 

 In addition to the hydrocarbon, there is present in balata some 40 

 per cent of resins and amounts of dirt, moisture and other impurities 

 which usually total about 15 per cent. The resins of balata are softer 

 than those of gutta percha and make the product in its raw state a 

 little less desirable than the better grades of gutta percha from the 

 mechanical standpoint. Balata, however, contains a smaller amount 

 of finely divided dirt or humus than gutta percha, which is reflected 

 in its superior electrical characteristics and lower water absorption. 



The resins of both gums have been usually included with the hydro- 

 carbon in making submarine insulation. Sometimes, however, a 

 portion of the resins are removed, partly to increase the toughness and 

 partly to improve the electrical characteristics. 



There are several methods which may be used for preparing gutta 

 hydrocarbon nearly free from resinous substances. One of these 

 methods involves dissolving the balata or gutta percha in warm 

 petroleum naphtha, filtering the solution from dirt and precipitating 

 the gutta hydrocarbon from solution by refrigeration, leaving most of 

 the resins in solution. A simpler and less expensive method, however, 

 is that of leaching out the resins by simply soaking the sheeted or 

 finely cut material in a suitable grade of petroleum naphtha at ordinary 

 temperature, followed by draining off the solution of resins and finally 

 evaporating the residual solvent from the extracted material. 



The completely deresinated hydrocarbon from either source is not 

 suitable for use alone as submarine cable insulation because insufii- 

 ciently plastic at safe working temperatures, as well as prohibitively 

 expensive. Otherwise the complete deresination of these products 

 would be highly advantageous as, for example, is indicated by the 

 superior electrical characteristics of deresinated balata shown in 

 Table I. A substantial amount of experimentation upon the methods 

 of refining balata has been necessary to secure the excellent electrical 

 characteristics therein indicated but no revolutionary innovation has 

 been necessary. 



TABLE I 

 Effect of Resin Content on the Electrical Characteristics of Balata 



Electrical Characteristics 0° C, 1 Atm., 

 2000 Cycles 

 Dielectric Specific Conductance 

 Material Constant Unit = 10"'= mho. cm. 



Balata 3.1 66 



Deresinated Balata 2.6 3 



Balata Resins 2i.2> 52 



In attempting to develop a new insulating material for deep sea 

 cables it seemed best to begin with gutta hydrocarbon as a basis, 



