a process for the deformation of a workpiece of an orientable , thermoplastic polymer by passage in the solid phase through a die having both an entry side and an exit side , which process includes providing the workpiece of the orientable , thermoplastic polymer which is initially present , at least in part , in an extended chain crystalline morphology at the entry side of the die ; causing the workpiece to deform in the solid phase through the die ; and collecting the deformed workpiece from the exit side of the die .