It’s not uncommon at Trelleborg to deal with customers and engineers who are not familiar with principles of polymer engineering. A customer’s experience can often be from a rigid pipe or structural background. Polymer materials can behave in unexpected or unusual ways! At Trelleborg we have a team of engineers and material scientists dedicated to solving your problems through applying our specialist knowledge to our products so that our products work for the long term.
These 4 top tips will help you understand the principles of polymer engineering.
- Top tip #1 - Stress and Strain
- Top tip #2 - Operating Temperature
- Top tip #3 - Water Absorption
- Top tip #4 - Hydrothermal Aging
Top tip #1 - Stress and Strain
When dealing with metals they usually behave in two distinct ways. An elastic response and plastic response. Most design is done within the elastic region which has a linear relationship to stress and strain. This makes the behavior much more predictable and easier to design with!
Polymers don't often exhibit this. Instead there are not usually linear relationships, so a strain-based design becomes necessary. Coupled with this they may exhibit a brittle behavior or an elastic behavior. Our engineers are used to this behavior and performing non-linear analysis. Get in contact and see how we can help advise and support your team on polymer applications subsea.
Top tip #2 - Operating Temperature
When dealing with metals they usually behave in a relatively stable manner over a large temperature range. Mechanical properties will usually stay quite consistent well past 100 degrees Celsius. Polymers however are much more sensitive to temperature. They usually have a temperature point in which their failure mode changes from glassy and brittle to elastomeric – known as the glass transition temperature and their mechanical performance can change dramatically even over a 10 or 15 degrees Celsius range.
Therefore, specifying the correct temperatures at both the installation and operation scenarios of your project can have a huge impact on design, from being overly engineered and expensive because of conservative assumptions or under engineered and highly stressed due to inaccurate design conditions. Our engineers and material scientists understand this behavior well and can even define it. Get in touch and see how we can help inform you and your team on the important principles of polymer and subsea design.
Top tip #3 - Water Absorption
When dealing with polymers it can be easy to think that they are ‘waterproof’ and in fact water resistant. Did you know that in fact most materials absorb water to some degree? To maintain successful operability of subsea equipment it is important to know the water absorption and its effects on mechanical properties through the life of the product.
Whether it is the effect on buoyancy, the change in bulk modulus, or reduction elongation at break then these affects can materially alter the performance. Our engineers are used to this behavior and understand how to test for and define it. Get in touch and see how we can help inform you and your team on the important principles of polymer and subsea design.
Top tip #4 - Hydrothermal Aging
It’s a misconception that all polymers are corrosion resistant and therefore suitable for wet or subsea environments. Whilst polymers don’t corrode in the way we may see a ferrous material corrode they material can still degrade! This is called hydrolysis. In actual fact the H2O (water) molecules can be very aggressive and attack the bonds within the polymer molecule chains. This hydrolyses the material weakening and degrading it rendering it useless for its designed applications. Temperature can also be a significant player in this. Just like the corrosion of metals, the break down through hydrolysis of polymers can be quickened through accelerated temperatures.
At Trelleborg our engineers and material scientists well understand this phenomenon. In fact, our in-house laboratory allows us to test and verify our subsea products for long term, hot and wet use. Get in contact and see how we can help advise and support your team on polymer applications subsea.
