Barus effect and melt distortion of an extrudate is the indication of viscoelastic nature of a polymer melt. Polypropylene-co-ethylene (PPcoE) filled with various amounts of sago starch were compounded using a co-rotating twin screw extruder and the extrudate blend swelling ratio and its appearance upon exiting the die at different screw speed and temperature were carefully analyzed. The Melt Flow Index (MFI) test and the morphology test using optical microscope (OM) were conducted to justify the obtained results. The addition of sago starch in PPcoE has significantly introduced a porous structure to the produced extrudates and the porosity became more obvious with the increasing amount of sago starch. Meanwhile, below 30 rpm screw speed, higher starch content generated lower extrudate swelling ratio. At constant screw speed of 30 rpm, a sign of flow instabilities occurred in the extrudate blends which can be directly evident from the captured OM image. In conclusion, the incorporation of sago starch in PPcoE has ultimately altered the melt strength of PPcoE which is concurrently reflected by the swelling behaviour and melt distortion of the blend.
