Protecting an underwater lighting unit

Electrochemicals manufacturer Electrolube was recently approached by a company in Australia for assistance with a particularly unusual application: the customer needed protection for an underwater LED lighting unit.

The encapsulation resin needed to be light blue for aesthetic purposes and had to be able to withstand water temperatures from 5–40°C, as well as being flame retardant. The customer specifically asked for a sample of a very flexible encapsulation resin that could resist attack from constant immersion in pool water. Critically, this could be salt water or fresh water.

Electrolube’s encapsulation resin was to replace the customer’s existing epoxy resin from a different supplier, which was causing problems with slight deformation of the base unit due to the exotherm. The desired resin needed to be highly resistant to both salt and fresh water immersion. Water naturally corrodes most metals due to electrochemical oxidation; however, when a salt water medium is used, the rate of oxidation is significantly increased due to the presence of dissolved sodium and chlorine ions.

Electrolube’s technical support team swung into action to resolve the problem as quickly as possible and offered two possible solutions: polyurethane resins UR5118 and UR5097. After further testing, UR5118 was discounted and the first production batch of UR5097 resin material was manufactured and shipped to Australia. Mike Woods, Electrolube’s Australia and New Zealand manager, together with Electrolube’s global business technical director for the Resins Division, Alistair Little, later visited the customer and discovered that there were a couple of issues with the material.

The first issue to overcome was the material had sedimented over time and was increasingly more difficult to reincorporate back into the resin mix. The second was that there was a slight bleed of resin through the gap between the resin and the LED unit. With a bit of lateral thinking, the logical solution was to increase the thixotropic nature of the resin, which would help to slow down the rate of sedimentation to an acceptable level and prevent the resin bleeding through the gap.

Following two weeks’ laboratory work, where a number of different options were tested, Electrolube’s R&D team produced a material that had sufficient thixotropy to slow down the sedimentation and prevent flow through the gap. The resin material was also still very easy to mix and pour into the unit; in fact, the increase in the mix viscosity of modified resin was only slightly higher than the original resin and the colour of UR5097 was altered to the desired colour shade, matching against an RAL standard. This produced a completely bespoke solution that effectively resolved the customer’s issues.

Importantly for this application, the resin is designed to withstand both fresh- and saltwater ingress and prevent the transmission of metal ions that could attack any metal present. The polymer used in the resin is also highly resistant to the transmission of water, even at various pressure differences experienced due to the depth of the water.

“We are delighted with the outcome of this particular application challenge,” said Electrolube’s managing director, Ron Jakeman. “At Electrolube, we are perfectly set up to solve issues for customers quickly and reliably with our international distribution, state-of-the-art in-house testing facilities and global manufacturing sites ready to deal with any challenges.

“We believe the proven quality of our products and easy product application processes, combined with our knowledge of the needs of LED manufacturers, helped assure the success of this project.”