There is a lot of UHMWPE rope on the market, often sold as "winch rope." This tends to be much lighter in weight compared to nylon of an equal strength, partly because it tends to be a much smaller diameter for an equal strength. I have heard that it is very slick, and therefore it is hard to tie a knot or hold a knot, but I cannot confirm that.
Let's just say that a normal nylon rope can be ascended with hardware if it is about 3/8ths inch diameter to 1/2 inch diameter. An equivalent UHMWPE rope might be only 3/16ths inch diameter for similar strength. Can that be ascended? Most of my ascender hardware will work with rope of 8-12mm, so I am thinking that UHMWPE is too small to be practical. It might possibly be OK for an emergency rappel rope as long as it is not too slick. But, if it can't be ascended, that may not help much.