Die Swell

The die swell effect is related to elastic memory and elasticity of the melt. The standard Rosand die swell measurement devices use laser micrometers to directly measure the diameter of the extrudate close to the die exit. This is usually carried out on the left hand bore (long die) only.

The measurement is interfaced directly with the control software and the die swell is stored as part of the measurement data file. Several laser die swell measurement options exist for the Rosand capillary rheometers. Single axis systems are suitable for most applications and measure the die swell in a fixed direction which is radial with respect to the die axis.

Alternatively, twin axis systems are also available to measure the die swell using two pairs of laser micrometers which are aligned with their axes of measurement perpendicular to each other. Standard resolution systems have an accuracy of 10 microns. High-resolution systems have an accuracy of 2 microns.