The results and comments on the effects of deep-ocean organisms on various 
nonmetallic test specimens which were assembled on bio-racks (Figure 25) are pre- 
sented in the Appendix. Close visual inspection of the recovered materials was 
performed under a stereoscopic microscope; insulation resistance and voltage break- 
down tests were conducted on electrical conductors; and compressive strength tests 
were performed on cylindrical coral concrete specimens. A breaking-strength test 
on rope specimens could not be conducted since these materials were completely 
deteriorated by marine organisms. (Note dangling rope specimens in Figure 25.) 
DISCUSSION 
From the results obtained on the biological deterioration of materials exposed 
on the ocean floor at a depth of 5,300 feet for a period of 35 months, it is concluded 
that nonmetallic materials such as pine and greenheart wood, Manila and cotton ropes, 
silicone rubber insulation, friction tape, and jute fibers including burlap coated with 
coal tar are susceptible to total biological destruction and are not suitable for deep- 
ocean use. : 
All of the plastic rod and tube specimens were deteriorated in various degrees 
by marine boring animals in an area where a wooden bait piece was fitted around each 
specimen; however, other areas of the plastic materials were not affected. Some of 
the plastic materials such as cellulose acetate absorbed a considerable amount of water 
as compared to other plastic rods (moisture analyses were not performed). A vinyl 
plastic tube (NCEL No. 15) lost its plasticizer or some other chemicals used in the 
formulation of this particular plastic by either the forces of deep-ocean environment 
or by microbial activity or both. This resulted in a loss of flexibility and a reduction 
in the original dimension of the plastic tube. Of the various types of electrical insu- 
lation exposed near the ocean floor, silicone rubber was deteriorated by the nibbling 
and biting action of some unidentified mud-dwelling marine organisms. Identical 
materials which were exposed about 8 feet above the sediment were not affected. 
Coral concrete specimens which were exposed about 10 feet above the sediment were 
not affected by marine borers. The concrete specimens placed at this height may 
have been subjected to attack by relatively few borers because it has been found 
that the greatest borer activity occurs near the sediment layer and starts to decrease 
above the sediment layer. 
The following nonmetallic materials were not affected by marine organisms or 
by the seawater environment at this particular test site, and these could probably be 
used for deep-sea application at this site: concrete; electrical cable insulation such 
as neoprene, butyl rubber, natural rubber, Teflon, polyethylene, FEP, Bakelite, PVC, 
and nylon; plastic electrical insulating tape; plastic films and sheets such as Saran, 
polyethylene, and acrylic; nylon nuts and bolts; rubber tubing (vacuum); nylon para- 
chute cords; and cable clamps made of ethyl cellulose. The electrical cables and 
plastic films listed above were exposed to seawater about 8 feet above the sediment 
and were not subjected to the activity of microorganisms of the sediment nor to a 
variety of mud-dwelling animals found inhabiting the bottom sediment. 
28 
