Sufficient rubber was eroded from the unprotected area of the cover to 

 cause the diameter to visibly neck down at the edges of the brackets. 

 This phenomenon was not observed on the synthetic-rubber-covered or 

 plastic-covered cables. Neither of the latter appeared to be affected 

 by 2-1/2 years of exposure either in the anaerobic bottom sediments or 

 in the aerobic near-surface waters. 



CONCLUSIONS 



Many synthetic polymeric materials can withstand prolonged exposures 

 in the ocean, either in the anaerobic bottom sediments or in the aerobic 

 near-surface waters. After 2-1/2 years in the ocean they underwent 

 essentially no measurable change in tensile strength or hardness. 



The durability of plastic polymers might be related to their level 

 of moisture absorption. Because of their extreme water repellency, it 

 is predicted that the following six polymers would be the most durable 

 in an ocean environment: polycarbonate, polyethylene, polypropylene, 

 polystyrene, polytetraf luoroethylene, and poly (vinyl chloride). Next 

 to the most durable in order of decreasing durability would be methyl 

 methacrylate, polyurethane, phenol-formaldehyde, and nylon. Hydrophilic 

 materials, such as cotton hemp and wood, are not durable in the ocean. 

 The wettability and durability characteristics of natural rubber fall 

 between the two extremes. 



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