I used 3/4" PVC and then used 1/2" electrical conduit. The conduit was too small so every four inches I wrapped duck tape around the conduit, about six wraps I think, to just enough that it would go into the 3/4" PCV with just a small amount of friction. It holds excellent (no sagging). As a matter of fact I made my whole frame for the back drop the same way. I just slip it all together when needed and take it apart for storing. Just don't sand or trim the ends of the PVC or the joints so they fit tight when put together. Ten foot section of electrical conduit, a section of PVC, and a small roll of duck tape under ten dollars.
Sorry forgot to add: Using a sleeve (coupling) you can glue it to one section of the PVC and then join two sections together say two 5' sections to make ten feet, the same can be done with the conduit but to make the PVC and the conduit stronger do not make the coupling of the two in the same spot. Say PVC at 5' and conduit at 6' for one section and 4' for the other.