Nanoclay Localization Effect on Melt Rheological Behavior and Microstructure of PP/PET Blend

Abstract

Dynamic and transient shear flow experiments along with TEM, SAXS and SEM analyses were performed for 75/25 and 25/75 (wt%/wt%) PP/PET blends containing two types of montmorillonite organoclays namely, Cloisite20A and Cloisite 30B. The weight ratio of Cloisite 20A to Cloisite 30B was equal to PP/PET weight ratio in the blend nanocomposites. The TEM and SAXS analyses revealed that all clays were almost localized at the interface of PP-rich blends whereas in PET-rich blends they were localized at both PET matrix as well as the interface ofthe blend. The SEM analysis showed that in a PET-rich system the size reduction of minor phase by addition of the organoclay was more than that of the PP-rich system. In contrast to the neat blend, the PP-rich blend nanocomposite showed thermo-kinetically stable phase morphology under annealing at a high temperature. In agreement with the morphological findings, the rheological investigations under oscillation shearflow field at low and high frequencies as well as those under transient shear flow field at low and high shear rates revealed that addition of organoclays to the blends had stronger effect on the rheological behavior of the PET-rich system as compared to that of the PP-rich blend. This was explained by the different localization of theorganoclays and the different weight ratio of the two types of clays in the PP-rich and PET-rich blend systems leading to a stronger network-like structure formation of clay layers in PET- rich blend nanocomposites.

Keywords

• rheology
• microstructure
• polypropylene
• Poly(ethylene terephthalate)
• blend