In 2008 34 world records broken all bar 1 were in the polyurethane suits.
This led to this ban by FINA ........ and the overall ban of the suits.
Slide 5 & 6
As a result of the structure of polyurethane and nylon it gives them these properties.
as you can see here and in my graph, it is clear that polyurethane is superior to nylon in most of its properties.
Polyurethane contains small parallel grooves to imitate the skin of a shark, reducing turbulence and therefore reducing drag.
Because of the covalent bonds stringing monomers in long it can rotate, letting chains stretch or fold. This is what gives polyurethane its high elasticity Modulus and high elongation at break.
It consists of very fine microfibers in a high-density weave to give a lightweight material which is also highly stretchable.
The elasticity combines support with flexibility. This means that not only can polyurethane be stretched
The covalent bonding of Polyurethane in long chains lock electrons to atoms, with none free to move, this is what forms the airtight seal on the suits, trapping the air between skin and suit, giving it the extra buoyancy.
According to Newtons First Law of Motion an object that is in motion will not change its velocity unless an unbalanced force acts upon it. Which translates to say that drag on a swimmer will increase the faster they swim.
Polyurethanes high elasticity modulus enables the suit to be ductile but also offer a high tensile strength. By compressing the swimmer’s body into a better hydrodynamic shape and by minimizing muscle oscillations it reducing form drag on the swimmer, allowing them to move faster through the water, with less effort.
Drag force is proportional to the square of speed, and the power required to overcome this drag is proportional to the cube of speed. This means that swimmers have to spend eight times more energy if they want to double their speed!
A swimmer encounters two main components of drag: form drag and skin friction drag.
To reduce Skin friction drag the material used has to have a smooth surface and cover lots of skin. To find the smoothest material with less drag Speedo collaborated with NASA and tested over 60 materials in a wind tunnel to find which had less drag, and the overall smoothest surface. thereby allow swimmers to achieve higher speeds without exerting extra energy or altering their swimming techniques
Buoyancy is a measure of how well the swimmer floats in the water.
The high compressive strain, given by the high elasticity of the polyurethane suits gives the swimmer a high hydrodynamic position in the water, and the smooth texture of the material also gives less resistance. This result in the suit having up to 38% less drag, This reduction in drag translates into approximately the swimmer being able to move 4% faster through the water.
Slide 11 & 12
As we can see in his graph of mens swimming speed in each event, it is clear to see that during the 2008 beijing olypimics, in which nearly all swimmers wore the high tech polyurethane suits, that the mens swim speed clearly peaked.
Here is just a quick video to show the effect the polyurethane suit has at the end of a race, in comparison to the old style nylon suits.