Rheological Measurements Performed

After a preheating time of about 10 minutes the pressure transducers of the MiniLab have to be calibrated at the selected measuring temperature, to avoid any temperature effect on the pressure measurement.

The pneumatic feeding piston and the extruder barrel are constantly purged by a constant Nitrogen flow, to avoid the presence of oxygen during the tests, and prevent degradation of the LDPE samples.

The sample is then feed into the running extruder by means of the pneumatic feeding piston.

After 1-2 minutes the extrusion pressure is getting equilibrated, what indicates that the sample is properly molten and ready for the rheological test.

The rheological test itself is performed and controlled by the HAAKE PolySoft OS Software. The software runs

The results of two independent runs with the same polymer are presented. the pre-programmed measuring steps (Fig. 2), checks when steady state conditions are reached and then measures thepressure drop between the pressure transducers in the slit capillary channel to calculate the shear stress