In reply to kylo-342:
Nylon and Polyester ropes have a slighty better abrasion resistance than polypropylene. Although polypropylene is typically found in rope sheaths that are designed to float on water, and is not common in typical ropes.
Like previously mentioned, look for a 11 or maybe 12mm rope if you want the most abrasion resistance. Perhaps a search of some caving forums would be of more help as static rope is more commonly used.
Another thing to think about is how the abseil rope is rigged. Is it possible to redirect / rebelay it past a sharp edge, can the abseil be rigged from a high branch of a large tree to allow it to bypass the edge of the crag completely? If neither is possible then a rope protector could be used, I find that a slit cut along the length of suitable diameter hose pipe makes a good rope protector that can be passed on abseil with relative ease, a bit of thin cord to act as a prussic to hold it in place, and some duct tape to help hold it closed can work work well. Or a carpet square / car mat can help pad out edges.