Is there a material that has higher kinetic friction than static friction?
You can assume it's sliding on any surface you want.
Better if you come up with one that has this property on a standard flooring material: steel, wood, smooth concrete, tile, asphalt, etc.
Also better if the material has this property at a macro scale.
Friction is not a property of a material, it is a property of the interface between two objects, which may be the same or different materials. One interface I can think of that has that property is a thin layer of grease -- the force required to move increases with velocity.
Sliding friction must, logically always be less than static friction. This becomes obvious when you look at it in terms of forces rather than coefficients.
Consider a block resting on a flat surface. You apply a small force to one side of the block to try to slide it along. Initially it doesn't move as the reaction force provided by friction increases in line with the force you exert.
Say that applying 10N of force is just enough to overcome static friction and get the block moving. Now if the sliding friction becomes greater the 10N force is no longer enough to overcome it and so it stops and your back to a static condition.
Another way to look at this is that friction is a reaction force so it can never be greater than the force applied otherwise you would be effectively getting work from nowhere.
However it is certainly possible to have materials whose friction properties change as a result of friction, for example carbon-carbon brakes are most effective at quite high temperatures.
There is also viscous drag which is proportional some function of speed although it is not really very meaningful to talk about static friction in this context.
The numbers for static and kinetic friction in aluminum-on-aluminum interactions, cited by @albseb back in 2016, are unreliable. Strangely though, they're the only published values.
I'm a physics student finishing my bachelor degree this year, and I'm doing my senior thesis with two other students on this exact topic - we may even try to publish it depending how much we can accomplish.
We've only just begun the project, but as far as we've found the values μs=1.05-1.35 and μk=1.4 seem to be the result of a ~30 year-long game of telephone. Without going into too much detail, we've found that a static friction value of 1.05 is somewhat reliable; we found it in the records of a 1940 MIT conference. However, the kinetic value is unfounded as far as we can tell. Following the rabbit hole of citations for the kinetic value of 1.4 led to a paper that did not support this number - a dead end.
What's interesting is how little published data there actually is on aluminum-aluminum friction. We're aiming to fix that in the coming months!
I dont think so. as kinetic force is always lesser than static. Here is a similar discussion
The link is about the theory behind the static and kinetic friction. the coefficient of static friction can never be less than the coefficient of kinetic friction. Having greater kinetic than static friction just doesn't make any sense.
