What is RHEON? | Stephen Bates, CEO.
As an engineer and material scientist by first degree, it was an easy decision to join RHEON LABS. Recognising it’s a long time since my ‘white-coat’ days, I leave the science here to the experts. It doesn’t mean I don’t understand and appreciate what they are doing, but the world of strain-rate sensitive polymers has moved considerably since my student days. Our founder Dr Dan Plant has been instrumental in moving that knowledge forward.
So what are we talking about when we refer to strain-rate sensitive materials? Most people have experienced examples of the ‘physical’ effects of mixing the correct proportions of water and corn-flour together: you can stir it slowly (and it seems runny) but try to stir it quickly and it stiffens up. You see the same effect as you run just where the sea touches the beach. Here the sand and sea-water mix behaves like concrete when you run, but you leave big foot-prints when you walk. What’s going on inside a material to make this happen? In a ‘physical’ example like this – one that we’d describe as mechanical – the water and solid particles are locking up because the two phases, liquid and solid, are both trying to control the mixture’s behaviour.
Imagine a crowded railway station concourse. You can walk across it by weaving around the other people and you feel no resistance – it’s just slow. Try to run and you’ll be bumping into people, progress will be resisted and it’s going to feel much more difficult. Neither you nor the other people have time to get out of the way and the concourse crowd has ‘stiffened-up’. In this example we’ve simulated a mechanical strain-rate sensitive material (we call these dilatants) using people and air-spaces to represent our solid and liquid.
So are we playing with corn-flour and sand at RHEON LABS? No we’re not. We’re much more excited by a different class of strain-rate sensitive material – ‘chemical’ dilatants. Chemical dilatants have many benefits over their mechanical counterparts. Whilst corn-flour style materials work in compression they have no resistance to tension – there is no glue holding the material together. The same is true of sand and water of course. If we are going to do anything useful with strain-rate properties we need to make a material that resists being stretched and compressed at speed.
Chemical dilatants work in a different way at a molecular level. The hydrogen bonds that exist between the molecules in our materials are the same bonds that stop water boiling until it’s at 100°C. They are very strong. For our materials to change shape they must break these bonds and have them reform in a different position. This can happen slowly but if we try to do it fast the material resists and requires more energy (i.e. force) to break the bonds. The material appears stiffer as it resists this force.
Let’s go back to our railway station concourse. Imagine everyone was now holding hands (bit weird I know – but bear with me). If you try to move through the crowd they would need to let go and take hold again as you pass. Feasible if you’re walking but even harder than before if you try to run. Hopefully you can see how the potential of the chemical dilatant is similarly much greater than its mechanical counterpart.
So why do we talk about energy-control at RHEON LABS? In effect what you’re doing if you change the shape of a chemical dilatant is breaking bonds at a molecular level. That requires energy. If that energy is coming from impact or vibration then you are going to use up or absorb some of that energy, and you – the user – won’t feel it anymore. If that’s in a glove or a helmet, it’s going to give your product some attractive characteristics. Early chemical dilatants like silly-putty (I’m showing my age here) were fun to play with but not much use for anything practical. When you left them alone they flowed like a liquid. What we have done at RHEON LABS is created “super” silly-putty that can be formed into shapes that stay put, or can be incorporated at a fibre or fabric level. This has made it possible to have the benefits of energy absorbing, chemical dilatants in a myriad of sports products.
Take a look at our website to explore how energy control can boost performance in your favourite sport www.rheonlabs.com