Novel Salt-Tolerant Water Blocking Materials for Marine Cables

The Navy depends on power supplies, sensors, and other electrical components for the adequate operation of submarines and surface vessels. These systems are connected and deployed using outboard cables, critical to their operation. The integrity of this crucial equipment is compromised after the watertight integrity of the cable jacket or connector is breached, allowing the longitudinal movement of seawater inside the core of the cables. To prevent the longitudinal movement of water, water blocking materials are commonly used. These materials may, 1) impede water transport down the cable by acting purely as a physical barrier, and/or 2) swell and retain water during a breach to sequester and block the water.  Numerous existing outboard cables used in Navy applications utilize water blocking agents that are soft and rubbery that serve to physically impede water transport. The problem with these commercial materials is that they often do not pass the water tightness low pressure test per MIL-DTG-915G for outboard cables. At high pressure (hydrostatic/open end test), the current water blocking material performs well. The Navy hypothesizes that the good performance is due to a compressing seal that is formed due to the high hydrostatic pressure. This sealing behavior is not present at low pressure, hence the need for new water blocking material solutions that can increase component lifetime and therefore mission readiness for the Navy. To address the Navy’s critical need for new water-blocking materials, Luna Labs will develop a modified seawater swellable natural rubber (WSNR) that will work as a physical barrier and quickly expand when the core of the cable is flooded with seawater. Our technology will be salt-tolerant, which means that its efficiency will not be affected by seawater as common water absorbent polymers. Since it will be based on a natural rubber, its environmental and toxicity will be much lower than synthetic rubber and must importantly, it will work at low and high hydrostatic pressure.