its neither, its polyurethane. And yes it can be fixed. If you have some autobody skills you can do it yourself depending on the severity of the damage, but if not there are companies that do nothing but refurbish busted bumper covers. Check your yellow pages for local companies. You may have to look under plating as most of these companies do chrome bumpers too so they offer chroming as a service. BUT, you will find that their charge for this service is close to the replacment cost of the bumper anyways, in fact its usually about the same as what they charge for a bumper they've already repaired and have in stock. May be cheaper to get one from a wrecker, you'll just have to price things out.
The bumper is hard to fix. When i got my car written off i could not have the bumper put to gether :shocked!: . I got another bumper instead yet it was damaged as well. It cost AUD$200 for the special glue which came in 2 parts. My panel beater did it and done a great job in glueing the broken bits together...
I paid about 30 bucks for the materials need to fix a torn bumper. If the thing is in multiple pieces your better of getting a new one, but if its just torn or scuffed it can be fixed relatively easily
If it's just scuff marks, no rips, then you can use bondo to fill it in. When I stuffed my Tbird into a rock face, I had some nasty scuff marks on my polyeurethane ground effects. I filled them in with bondo and repainted the front skirt. It's been years and you can't tell that it was ever bondoed. Still looks great.