A method for controlling the viscoelastic properties of a polymer
comprising the steps of feeding a polymer melt into a first and optional
subsequent means for applying a strain rate, each means for applying a
strain rate being underfed or overfed according to the relative
volumetric flow rates into the out of each means for applying a strain
rate. The method further comprises subjecting the polymer melt in the
means for applying a strain rate to a total shear rate that comprises
contributions selected from the group consisting of pressure flow through
an orifice, rotational flow about an axis that is parallel to the
direction of flow of the melt, vibration in the transverse or
longitudinal direction relative to the flow direction of the melt, and
any combination thereof. The flow profile history that the polymer melt
is subjected to is controlled by the choice of first, optional second and
optional subsequent volumetric flow rates, the temperatures of processing
in the first, optional second and optional subsequent means for applying
a strain rate, and the shear rates exerted by the pressure flow,
rotational flow and vibration in each or any of the first, optional
second and optional further means for applying a strain rate. There are
optionally intermediary zones in between the first means for applying a
strain rate and the optional second means for applying a strain rate or
the optional second means for applying a strain rate and the optional
subsequent means for applying a strain rate or both, and the temperature
in the optional intermediary zones are optionally used for control of the
flow profile history of the melt.