Figure 28. Deep cracks in neoprene rubber insulation. The wire 

 was exposed to seawater. 



Electrical Cable Insulation for Single Conductors and Multiconductors . The 

 insulations of the 10-inch-long electrical cables (Figure 26) were examined under 

 a stereoscopic microscope for signs of any biodeterioration and for any physical 

 effects of the deep-sea environment. 



Biodeterioration due to borer activity was more pronounced (especially in the 

 area of a wooden bait piece) on a set of electrical cable insulations which were 

 exposed about 0.5 foot above the sediment layer than on an identical set of insula- 

 tions which were exposed about 3 to 4 feet above the sfediment. The insulating 

 materials which were damaged by the borers under a wooden bait piece were Teflon 

 (Figure 29), polyvinyl chloride, silicone rubber, bakelite, polyethylene, nylon, 

 and fluorinated ethylene propylene. The insulating materials which were neither 

 affected by borer activity nor by the deep-sea environment were butyl rubber, 

 neoprene rubber, and natural rubber. 



In addition to damage by borer activity under the wooden bait piece, the 

 surfaces of the silicone rubber insulations were damaged by the nibbling and biting 

 action of some marine organisms. As a result of this type of damage over the entire 

 surface area (except underneath the area of cable clamps), the thickness of the 

 insulation was reduced considerably (Figure 30). 



35 



