Rubber and Silicone Forming: Tubing, Sheet, O-Rings and Bands

Rubber is shaped soft and then cured, the curing locking its shape and giving it its spring. Natural rubber is mixed on a two-roll mill with sulfur and activators such as zinc oxide; silicone rubber comes as a ready compound. Tubing is extruded through a ring die and cured with heat; rubber bands are extruded tube cured on mandrels and sliced across. Sheet is calendered between rolls and cured. O-rings and gaskets are compression moulded: a measured charge is laid in a heated mould cavity, the press closes, the heat cures it, and the thin flash is trimmed off.