i took the time to separate each material type to an individual obj. took some time, but there were objects with multiple materials on one mesh. most of the times, this is easiest and of course you don't have make your poly selections from scratch !
btw. the models are named after the original assigned material
have fun !
zip file and in case the zip file doesn't open (created on a mac, this causes problems sometimes), the eleven objs are also there.