Effects of blend composition and compatibilization on the melt rheology and phase morphology of binary and ternary PP/PA6/EPDM blends

Ternary blends based on isotactic polypropylene (iPP) modified by polyamide 6 (PA6) and ethylene-propylene-diene terpolymer (EPDM) were prepared and their rheological properties were studied. The total content of dispersed phases was kept fixed at 30 wt%. The goal was to investigate the effect of blend composition and compatibilization process using PP-g-MA on the dynamic viscoelastic properties of PP/PA6/EPDM ternary systems. Then, attempts were made to correlate the viscoelastic response of the blends with their morphological texture as examined by SEM technique. Different rheological behaviors were observed depending on the dispersed phase(s) type, concentration and alteration of interfacial interaction between the phases. In the blends containing PA6 phase, compatibilization process led to a significant change in the morphology of the blend with a subsequent change in the viscoelastic properties, especially at low-frequency regions. Rheological analysis revealed a deviation from liquid-like behavior for certain binary and ternary systems which were dependent on the PA6 and EPDM contents and the microstructure of the blends as well. In the case of ternary blends, separated-type morphology was observed in consistent with morphology predicted by spreading coefficient concept. The relationship between the morphology and relaxation process of the individual particles was also discussed.