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BELL SYSTEM TECHNICAL JOURNAL 



Preparation of Paragutta 



As previously stated, the principal constituents of paragutta are 

 deproteinized rubber and purified gutta hydrocarbon. Specially 

 treated hydrocarbon or montan waxes may also be added as a third 

 constituent to modify mechanical properties and reduce cost. The 

 proportions of these constituents may be varied over a wide range to 

 achieve the desired characteristics, but in general rubber and gutta 



2 3 



TIME IN WEEKS 



Fig. 3 — Effect of washing and removal of proteins on resistivity of crude rubber, 

 when immersed in 3.5 per cent NaCl solution at room temperature. 



are used in about equal proportions and purified montan wax may be 

 added up to about 40 per cent. Superior electrical properties, how- 

 ever, result from the use of hydrocarbon waxes, which may be added 

 in amounts up to about 20 per cent. By the proper blending of these 

 materials, a thermoplastic insulation is obtained which closely ap- 

 proximates gutta percha in mechanical properties and is fully its equal 

 as to electrical stability in water. Its specific electrical characteristics 



