Table 9. Breaking Strength of Rope Specimens Before and 

 After Deep-Sea Exposure 



Rope 



Diameter 

 (in.) 



Breaking Strength (Ib)!^ 



Before 

 Exposure 



After 

 Exposure 



Cotton 

 Manila 

 Nylon 

 Polypropylene 



1/2 

 1/2 



1/4 

 5/16 



1,340 

 2,068 

 1,900 

 1,810 



02- 



0^ 



1,930 



2,040 



\j Average of two specimens for each test. 



2j Estimated 100% of tensile strength of rope destroyed by microorganisms 

 and borers. 



Moisture absorption analysis was performed on the plastic rod and tube 

 specimens. In order to determine the amount of moisture the plastics had absorbed 

 during the deep-sea exposure, each of the 3-foot-long plastic specimens was 

 weighed before being submerged. The figures for weight could not be used in the 

 test because of the weight loss in the plastics as a result of marine borer attack. 



For the moisture absorption study, a section about 3 inches long was cut from 

 each of the 3-foot-long plastic specimens which were stored in plastic bags aboard 

 ship; the section was then weighed in the laboratory. After being weighed, the 

 test specimens were dried at room ambiency for 1 month and were then reweighed. 

 The information about the amount of moisture gained by the plastic test specimens is 

 presented in the Appendix. 



Wrappings Around Plastics . Except for the tape wrapped around vinyl tube 

 No. 338, the plastic electrical insulation tape (Figure 23), which was wrapped 

 around the plastic rods and tubes, was attacked by marine borers. The small 

 l/32-''inch-diameter holes were found along the edge of the overlap, but the borers 

 did not penetrate the plastic tape. The deepest holes showed that some borers had 

 penetrated approximately three quarters of the way through the 0.010-inch-thick 

 electrical tape. It is believed that this is the deepest the borers are able to pene- 

 trate directly into the tape. 



30 



