RESISTANCE OF MATERIALS TO MARINE BIOLOGICAL ATTACK 1107 



tains a combination of polyester E and di-2-ethylhexyl phthalate (DOP), 

 and one in Table V plasticized with polyester A. These polj^esters are 

 fatty acid-type compounds. Typical oxygen consumption values for 

 three different polyvinyl chloride plastics, representing different rates 

 of utilization by the bacteria, are plotted in Fig. 3. As noted in Table I, 

 \ery low concentrations of organo-metallic stabilizers and fatty acid 

 lubricants were in all the compounds tested except the resin alone. How- 

 ever, of the three materials which contained no added external plas- 

 ticizer only the rigid plastic is utilized. This material contained about 

 8 to 10 times as much fatty acid lubricant as the other two compounds. 

 Two casting resins were tested, one an epoxide (Table V), and the 

 other a silica-filled styrene polyester (Table VII). Under the conditions 

 of this test, the epoxide resin is not utilized by the organisms. In the 

 case of the styrene polyester, results are less conclusive. After eight 

 weeks, an oxygen consumption value 5.4 ppm higher than that for the 

 controls suggests the possibility of attack. Additional tests are planned 

 with this material to obtain more data on which to base a final decision. 

 . As might be expected, the jute fibers are quite susceptible to attack ; all 

 oxygen was consumed from the test medium between the fourth and 

 I eighth week (Table V) . The fact that results in the same test run with 

 I the polyvinyl chloride compound plasticized with polyester A show that 

 j all oxygen was consumed from the test medium in 17 days does not mean 

 I that this latter compound is more susceptible to attack than jute. In 

 I the jute, bacterial attack is necessarily restricted to a progressive surface 

 attack, but with the polyvinyl chloride compound, leaching of the sus- 



Table IX — Hydrogen Sulfide Production by Marine Bacteria 



IN Anaerobic Sea Water Test with Polyethylene 



as the Only Source of Organic Carbon 



Test Material' 



2.0 melt index2 



0.2 melt index (Source A) 



0.2 melt index (Source B) 



0.2 melt index + antioxidant 



0.2 melt index + 5% but 3d rubber -f- antiox. 

 0.7 melt index (High Density) -f- antiox.. . . 

 Controls (inoculated sea water) 



H2S Production After Weeks of Incubation 



ppm 



0.22 

 0.22 

 0.22 

 0.22 

 0.22 

 0.22 

 0.10 



8 



ppm 



0.32 

 0.29 

 0.32 

 0.64 

 0.32 

 0.22 

 0.64 



12 



ppm 



0.22 

 0.45 

 0.26 

 0.35 

 1.31 

 0.29 

 0.70 



16 



ppm 



0.38 

 0.58 

 0.24 

 0.45 

 0.58 



* Except where noted polymers are low density grades manufactured by the 

 high pressure process. 

 2 ASTJM pi 238 

 ' Insufficient samples 



