Real time measurement and control of viscosity for extrusion processes using recycled materials

Bao Kha Nguyen, Gerard McNally, Alan Clarke

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


The aim of this paper is to develop a new generation of extruder control system for recycled materials which has ability to automatically maintain constant a polymer melt viscosity of mixed recycled polymers during extrusion, regardless of variations in the Melt Flow Index (MFI) of recycled mixed grade high density polyethylene (HDPE) feedstock. The variations in MFI are due to differences in the source of the recycled material used. The work describes how melt viscosity for specific extruder/die system is calculated in real time using the rheological properties of the materials, the pressure drop through the extruder die and the actual throughput measurements using a gravimetric loss-in-weight hopper feeder. A closed-loop controller is also developed to automatically regulate screw speed and barrel temperature profile to achieve constant viscosity and enable consistent processing of variable grade recycled HDPE materials. Such a system will improve processability of mixed MFI polymers may also reduce the risk of polymer melt degradation, reduce producing large volumes of scrap/waste and lead to improvement in product quality. The experimental results of real time viscosity measurement and control using a 38 mm single screw extruder with different recycled HDPEs with widely different MFIs are reported in this work.
Original languageEnglish
Pages (from-to)212–221
Number of pages10
JournalPolymer Degradation and Stability
Early online date25 Jan 2014
Publication statusPublished - 2014


  • Viscosity; Real time, Control, Recycled Polymers


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