Hi shan808,
You can read a little more about fiberbeds or down alternative mattress pads (both of which use polyester fibers) in post #2 here and post #10 here.
They are more of a “feel” item than foam toppers and provide pressure relief that is more “point specific” and are also less resilient and supportive than foam.
They are also more breathable than foam although they don’t regulate temperature as well as natural fibers such as wool.
Phoenix