###What each suit was composed of depends on which era of the Flash you are talking about. Each one had a different suit and different properties. BUT, and this is the most important part:
None of his/their suits had any particular property that protected them from destruction. The protection came from the Flash's speed-force generated aura.
The Flash's body is surrounded by what he calls his "speed force aura". This aura protects him and anyone who is running with him or carried by him, from the effects of using his speed. This includes friction and airborne particulate matter.
It also protects him from injury from high speed impacts such as punches he delivers and receives from his opponents. With this aura, he is able to absorb kinetic energy. He possesses a level of superhuman resistance to injury which at times does extend far past normal physical interactions, as received from normal combat.