Flow characteristics of degraded polypropylene-co-ethylene kaolin composite extruded at different temperatures and extrusion cycles using single-screw extruder

• Published in: Iranian polymer journal 2021, Vol.30 (11), p.1201-1210
• Main Authors: Abdul Rahim, Nor Azura, Ariff, Zulkifli Mohamad, Abd Jalil, Jalilah, Ariffin, Azlan
• Format: Article
• Language: English
• Subjects: Ceramics; Chain scission; Chemistry; Chemistry and Materials Science; Cleavage; Composites; Crosslinking; Degradation; Die swell; Ethylene; Extrusion dies; Extrusions; Flow characteristics; Flow distribution; Glass; Kaolin; Maleic anhydride; Melt flow index; Natural Materials; Original Research; Polymer matrix composites; Polymer Sciences; Polypropylene; Rheological properties; Shear forces; Single screw extruders; Swelling ratio; Viscoelasticity; Viscometers
• ISSN: 1026-1265; 1735-5265
• DOI: 10.1007/s13726-021-00969-y

Melt processing is challenging for recycling of mineral-filled polypropylene (PP) composites because the melt flow system, the viscoelasticity and the appearance of the extrudate profile change due to a combination of extensive shear forces and thermal-oxidative degradation. The flow pattern and the swelling behaviour of polypropylene- co -ethylene-kaolin (PP- co -E-kaolin) composite with 20% (by wt) kaolin and 5% (by wt) maleic anhydride- graft -polypropylene (PP- g -Ma) were distinguished using a single-screw extruder operated at different die temperatures and extrusion cycles. The compound was prepared by mixing the ingredients using a heated two-roll mill, whereas the composite rheological and die swell measurements were obtained from the single-screw extruder. Confirmation of the obtained flow behaviour was evaluated using an Ubbelhode viscometer and a melt flow index (MFI) tester. The apparent viscosity ( η app ) of molten composites and the swelling ratio ( B ) of extrudates decreased with increasing the extrusion temperature, reflecting the PP melt strength weakened with increasing the amount of viscous component. At the same time, increasing MFI values also indicate the production of lower molecular weight PP- co -E composites. This was caused by the backbone chain-scission reaction due to the thermal-oxidative degradation in the PP- co -E matrix. Meanwhile, in the case of multiple extrusion cycles, a gradual increase in the composite molar mass ( M v ) and B justified the development of chemical crosslinking in the PP- co -E-kaolin composite extrudates.