what are the materials of the work in rapidprototyping?

Answer 1

One form uses a liquid plastic that polymerizes when a laser scans across it forming a solid. The support is lowered a few thousandths after each layer is hardened so the shape can be built up.
Another uses liquid PVC to build up the piece, kind of like laying toothpaste down from the tube to build walls, except it hardens.
The reference discusses a number of different materials.