Plastic Specimens. The S-foot-long plastic rods and vinyl tubes, recovered 

 after 13.4 months on the sea floor in 2,370 feet of water, are shown in Figure 28. 

 There were numerous borer holes, both deep and shallow, underneath the area where 

 the wood bait pieces were fitted over the lower and upper sections of the plastics 

 (Figure 29). Generally, the lower section, exposed about 0.5 to 1 foot above the 

 sediment layer, had more borer holes than the upper sections which were exposed about 

 3 feet above the sediment. In other words, the borers were found to be more active 

 near the sediment than 3 feet above the sediment layer. 



The following plastic sheet, rods, and vinyl tubes were damaged by borers 

 under the wood bait piece: delrin, nylon, phenolic laminates, polycarbonate. Teflon, 

 cellulose acetate, extruded acrylic, polystyrene, and vinyl tubes (NCEL Nos. 424 

 and 425). Polyvinyl chloride pipe (unplasticized), polyethylene, cast acrylic, and 

 a vinyl tube (NCEL No. 422) were not damaged by borer activity under the bait 

 piece. 



These borers were also able to bore into the surface of certain plastic materials 

 directly from the seawater environment without the aid of any wood bait piece. On 

 some plastics such as on polystyrene, the attack occurred along the edge of plastic- 

 tape wrappings (Figure 30). On a vinyl tube (NCEL No. 425), there were as many 

 as 300 shallow borer holes, and many of these holes contained immature borers 

 (Figure 31). The deepest penetration into plastic by these borers occurred on a solid 

 phenolic laminated plastic rod (NCEL No. 415). Several borers had penetrated over 

 l/l6 inch into this plastic, and the shells of these borers were about 1/16 inch in 

 diameter (Figure 32). The following plastics were also attacked by the borers 

 directly from seawater: delrin, polycarbonate, cellulose acetate, polyethylene, cast 

 acrylic and polystyrene rods; and vinyl tubes (NCEL Nos. 424, 425, and 426). These 

 are shown in Figure 33. The number and size of the borer holes found on the surface 

 of the plastic specimens are presented in the Appendix. 



A vinyl tube (NCEL No. 412) intended for low-temperature use had a heavy 

 bacterial slime growth over the entire tube and over the plastic, rubber, and burlap 

 wrappings; the other three vinyl tubes intended for various other uses had a light 

 slime growth over the entire surface. Perhaps the vinyl tube (NCEL No. 412) contains 

 a plasticizer or some other chemical which serves as a source of food for the growth 

 of microorganisms. 



Moisture absorption and hardness tests were performed on the recovered plastic 

 specimens which had been stored in plastic containers filled with fresh seawater 

 aboard ship. These tests were conducted In a room which was kept at a constant 

 temperature of 23°C and a relative humidity of 20%. The information about the 

 amount of moisture absorbed and the hardness of these plastic materials is presented 

 in Table 5. 



29 



