PDM Neptec and Portsmouth University are using a DTI Knowledge Transfer Partnership (KTP) to develop accelerated life testing of underwater cable connector assemblies. This will provide PDM with the tools to evaluate new processes and materials as the marine industry prepares for the effects of environmental legislation and the inevitable impact on processing materials.
PDM have extensive experience in delivering reliable connectivity solutions for sub-sea applications but formerly did not have a method for accelerated life testing to develop enhanced processes. Under the KTP, the Applied Electrochemistry and Microbiology Group at Portsmouth University is evaluating lifetime performance in aggressive marine environments. They are exploring new research and exposure trial testing to deliver tools that can be used by PDM. The goal of the project is the development and testing of novel primer/polymer systems in order to promote optimal stability of connector assemblies for underwater applications in marine, oil and gas, and defence applications.
Starting in 2007, the project sought to establish the baseline performance level of moulded assemblies. Test structures were designed to measure adhesion and the project began with comparisons of standard ASTM salt spray tests, flowing seawater tanks and an exposure raft in Langstone harbour. These tests use a lot of resources and take a long time to provide results. This important phase created the baseline measurements on current products with the results showing that tests in the flowing seawater tests are comparable with full immersion tests on the seaborne raft without the complexity and concerns associated with keeping structures in the harbour. These flowing seawater trials will be ongoing as the project continues.
In the marine industry an important potential failure mechanism in cable connector assemblies is Cathodic Delamination. This is the failure of metal-to-polymer bonds due to localised reactions which occur on cathodically polarised metal surfaces while immersed in an electrolyte, the sea. This phenomenon is characterised by the loss of adhesion between the polymer and metal substrate which results in system failure. Through the KTP, Cathodic potentials, which are detrimental to polymer-to-metal bonds have been identified and polyurethane material systems are being designed to resist the effects of this, thus offering longer life expectancy.
To provide faster feedback, PDM have constructed a test cell for life testing where the effects of Cathodic delamination can be accelerated. Effects can be generated in tens of hours and provide feedback to new developments. The industry needs to be ready to deal with changes to materials as a direct result of the REACH and COSHH legislation and the selection of primers and polyurethane catalysts. Mercury is commonly used as a catalyst in polyurethane, and the environmental impact is under review even at the very low levels in cables and connectors; it is already banned in Norway to protect the salmon farming industry.
Responding to this legislation, new material systems are being evaluated to respond to legislation that seeks to eliminate the use of mercury in polyurethane systems. PDM is working with polyurethane suppliers and developing in-house processes to ensure that these changes do not diminish the current performance levels of these important cable assemblies in deep marine environments.
With the Knowledge Transfer Partnership, PDM is at the forefront of this work and will continue to supply connectors and cables for underwater usage that provide users with the lifetime they require.