Scanning electron micrographs of fluorocarbon rubber (FKM) and FKM and hydrogenated acrilonitrile-butadiene rubber blends of varying compositions; (a) 100% FKM, (b) 80/20 FKM/HNBR, (c) 60/40 FKM/HNBR, (d) 40/60 FKM/HNBR, (e) 20/80 FKM/HNBR, (f) 100% HNBR.