Issues associated with cable jacket materials intended for use in polar environments

The extremely cold environment experienced by outboard cables used in the Earth's polar regions necessitates careful selection of polymers for use as jackets. The U.S. Navy has two specifications for neoprene (polychloroprene) cable jackets - one designated “Arctic neoprene” because of its extreme low temperature flexibility requirement (-54°C) and the other designated by default as “standard neoprene” (with a low temperature flexibility requirement of -25°C). These neoprene formulations are controlled by performance, rather than compositional specifications. During the past decade, a latent defect in the form of “wax blooming” has been encountered with some “Arctic neoprene” formulations. As the wax migrates to the surface of the cable jacket, it tends to debond other materials bonded to the jacket (such as polyurethane overmolds for connectors or splices), thereby jeopardizing the parent cable's watertight integrity. Because these wax-initiated debonds do not occur rapidly, the long-term viability of any proposed solution is crucial for solving the problem. For example, the rubber formulations could be modified to prevent the wax from blooming, but the effects of any such changes on other, desirable material properties, such as low temperature flexibility, would need to be determined. The question of whether the “wax blooming” problem would be more problematic for cables actually used in the Arctic is unclear, because of conflicting trends within the cable jacket neoprene. Colder service temperatures would lower the diffusivity of the wax within the neoprene, thereby tending to slow the wax blooming process, while the solubility of the wax in the neoprene would decrease at colder temperatures, thus worsening the wax blooming process. Another complicating effect is the absorption of water by the neoprene cable jacket - a process that would accelerate the blooming of the wax because polar neoprene rubber has a greater affinity for polar water molecules than non-polar wax molecules. A final consideration is whether there is any true need for an outboard cable jacket with such a low temperature flexibility requirement as that specified for “Arctic neoprene” - if not, then the problem could be resolved by always specifying the use of “standard neoprene” for marine outboard cables used in cold environments.