One type in the UK is called 'Vilene'
This is usually on a roll and can be either iron on or non-iron; this is usually thicker, but both kinds can be bought in different weights.
It usually comes in black (more dark grey really) or white.
(Before the boys were born and I had time
I used to make some of my own clothes!
)
This material is very much like that used for the schooner and corsair sails and I always thought it was the same for the tent/stall awning pieces, although looking at my circus horse tent, the back of that does feel a bit more rubbery.
Elaine