Well, in the US, we had 1943 pennies (oops, one cent pieces...) made form iron. Man, do they rust in the Florida humidity. In 1944-45, the pennies were made from spent shell casings made from copper. since 1982, the penny is virtually 99% zinc, and about 1% copper, if that nowadays.
Many countries use aluminum in their coinage; it was popularized by several European nations during World War II. I think France was the first to try it. They also rust in South Florida, and look lousy.
Plastic money may indeed last longer than cotton/paper money, so it's a good idea. You don't want to know how many germs are in a dollar bill, and you probably don't want to think about where it came from. Just wash your hands before meals, if you're a cashier!
Plastic money will last longer, for paper money usually gets removed from serivce after about 8-10 years, unless it's a $100 bill or some wierd thing like a $2 bill (brief appearance in 1976, but you still get them every now and then). Every time I see one in a cash drawer, I ask for it! Same goes for 50 cent pieces, and other wierd stuff like that.
So paper money will probably go the way fo the dodo, because plastic must be a lot more difficult to counterfeit in the long run.
