Evolution of morphological and rheological properties along the extruder length for blends of a commercial liquid crystalline polymer and polypropylene

The main aim of this work is to study the morphological and rheological evolution during extrusion of blends of polypropylene and a commercial liquid crystalline polymer, Rodrun LC3000. This study was performed for blends with 10, 20 and 40 wt% LCP, processed at 220 and 240degreesC. For this purpose, a special collecting device was used that allows the removal of samples at different locations along the extruder length. The results of the morphological study revealed that the mean diameter of the LCP structures decrease as they proceed along the extruder axis. The rheological properties were also studied ex situ both in the linear and in the non-linear regime. From the results obtained in oscillatory shear it was observed that the elastic modulus and the complex viscosity decreases from the beginning to the end of the extrusion process, reaching a minimum for the final extrudate. FT rheology was used to study the non-linear viscoelastic behavior and the results also show marked difference between samples collected at various stages of the process, the ratio I(3omega(1))/I(omega(1)) decreasing along the extruder. (C) 2004 Elsevier Ltd. All rights reserved.