Table 3. Materials Used in the Formulation of Insulating 

 Materials Tested 



Test Specimen 



Plasticizer 



Filler 



Antioxidant 



Polyethylene (standard 

 polyethylene insulation) 





- 



- 



Polyvinyl chloride 



- 



- 



- 



Government rubber 

 styrene (styrene 

 butadiene rubber) 



cumarone-indene 

 resin and micro- 

 crystalline wax 



hard clay and 

 water-ground 

 whiting 



polymerized 



trimethyl 



dihydroquinoline 



Silicone rubber 



- 



- 



- 



Neoprene (type W) 



light process oil 

 and petroleum 



hard clay 



4, 4 thiobis (6-tert- 

 butyl m-creosol) 



RESULTS 



Marine Growth on STU Anchorage Complex 



All the components of the STU anchorage complex (polypropylene rope, pinger, 

 aluminum buoys, shackles, and a concrete sinker connected to the STU riser line) 

 were recovered after being exposed in the sea for 12 months, although the STU itself 

 was not recovered for another 12 months. 



The section of a 1 -inch-diameter braided polypropylene lift line (inverted 

 catenary line) which connects the STU to the riser line was the first item to be 

 hauled aboard ship. Attached to this buoyant rope were large gooseneck barnacles 

 (Figures 4 and 5) whose shells were about 1.5 inches long. There was also a moderate 

 growth of hydroids on the rope. When the barnacles were first observed on the rope, 

 it was suspected that the inverted catenary lift line was severed and was no longer 

 connected to the STU. These barnacles are normally found on the surface of the 

 water, which indicated that the rope was floating on or near the surface of the water 

 for long periods. If the 6,000-foot-long inverted catenary lift line had been attached 

 to the STU and to the riser line as planned, the rope would have been exposed about 

 1,000 feet below the surface and there would have been no barnacle growth on it. 



The suspicion that the rope may have been severed was verified when the loose 

 end of the rope was hauled aboard ship. Without the lift line, the task of retrieving 

 the STU was made much more difficult. A grapple was lowered to the bottom of the 

 sea and the 6,000-foot-long wire rope which is attached to the STU and stretches out 

 across the sea floor was seized. 



