Phase morphological evolution and rheological properties of polypropylene/ethylene–octene copolymer blends

The morphological evolution during extrusion and rheological properties of polypropylene (PP) and ethylene–octene copolymer (EOC) blends were studied. The phase morphology of the blends at different locations along the extruder length was investigated by scanning electron microscopy (SEM). The PP/EOC (70/30) blends has already formed a well-established droplet/matrix morphology at Valve 3, and an elongation of particles was observed from Valve 3 to extruder die. The phase-separated PP/EOC blends within the linear viscoelastic regime display higher than expected values of storage modulus at low frequencies. The effect of the deformation of phase domain on the rheological properties of the blends, the small constant strain amplitude within the linear viscoelastic regime does not substantially alter the droplet shape of the dispersed phase and yields a linear viscoelastic response, but the large strain amplitude destroys the dispersed phase domains, and eventually results in shear-induced mixing or homogenization.