  The blends and hybrid nanocomposites of polypropylene - cycloolefin copolymer
were prepared by a twin-screw extruder followed by microfibril formation using
a single screw extruder. The effects of shear rate and organoclay on the
morphology of polypropylene - cycloolefin copolymer (PP/COC - 80/20 wt. %)
blends were studied by using a combination of rheological measurements, X-ray
diffraction (XRD) and scanning electron microscopy (SEM). It was found that
although the viscosity ratio of PP/COC blend was unfavorable for COC droplet
deformation, the COC phase was converted to finely dispersed fibrils in PP
matrix. This could be asserted to the high elasticity of the COC droplets that
suppressed the droplet breakup in the favor of fibrillation process. The high
glass transition temperature of COC (140 degree centigrade) could also assist
restoring the generated microfibril morphology upon cooling. The experimental
results also depicted that the droplet deformation and microfibril formation of
PP/COC/organoclay nanocomposites mainly depend on the organoclay partitioning,
which could be controlled predominantly by kinetic parameters. While the
localization of organoclay in the PP matrix resulted in smaller COC droplets
and fibrils with smaller diameter, the presence of organoclay inside COC
droplets reduced the droplet deformability, leading to fibrils with larger
diameter.
