A new homemade apparatus

i.e.

vibration assisted extrusion equipment

is employed to extrude polypropylene. Vibration assisted extrusion is based on the application of a specific macroscopic shear vibration field. Reduction of apparent melt viscosity as a function of vibration frequency is measured at different screw speeds and die temperatures. The effect of the process is investigated by performing mechanical tests

differential scanning calorimetry studies

polarized light microscopy and wide-angle X-ray diffraction. It is found that

compared with conventional extrusion

vibration assisted extrusion could effectively improve the rheological properties of PP melt by incorporating an extra shear vibration field. Both the tensile strength and elongation at break increased under the shear vibration field. For vibration assisted extrusion samples

both the melting temperature and crystallinity increased

accompanied by remarkable grain refinement. Vibration assisted extrusion induced a significantly enhanced bimodal orientation with a high fraction of

a

*

-oriented

α

-crystallites

while only a limited improvement in the flow direction orientation. A structural model

i.e.

bimodal

c

-axis and

a

*

-axis orientation of PP macromolecular chains

was adopted to explain the experimental results.