Tubular materials.

摘要

Tubular workpieces of oriented polymers such as polyethylene olyester and PVC are formed by drawing a workpiece (5) over an expanding former (1) in the absence of any force perpendicular to the axis of the workpiece. The processes do not require the use of any liquid lubricant. They enable greater degrees of expansion and hence orientation in the direction perpendicular to the axis to be achieved and result in products of improved appearance and strength.