Real-Time Monitoring of Pellet Plastication in a Full-Flight Screw and Kneading Disk Elements of a Co-Rotating Self-Wiping Twin-Screw Extruder by Acoustic Emission (AE) Sensing

Tsukasa Kida; Masatoshi Ohara; Keigo Inamori; Shogo Nagasawa; Shin-Ichi Kihara; Kentaro Taki

doi:10.3390/polym15051140

Real-Time Monitoring of Pellet Plastication in a Full-Flight Screw and Kneading Disk Elements of a Co-Rotating Self-Wiping Twin-Screw Extruder by Acoustic Emission (AE) Sensing

Polymers (Basel). 2023 Feb 24;15(5):1140. doi: 10.3390/polym15051140.

Authors

Tsukasa Kida¹, Masatoshi Ohara², Keigo Inamori¹, Shogo Nagasawa¹, Shin-Ichi Kihara³, Kentaro Taki⁴

Affiliations

¹ Department of Natural System, Graduate School of Natural Science, Kanazawa University, Kanazawa 920-1192, Japan.
² Shibaura Machine, Numazu 410-8510, Japan.
³ Graduate School of Advanced Science and Engineering, Hiroshima University, Higashihiroshima 739-8527, Japan.
⁴ School of Frontier Engineering, Kanazawa University, Kanazawa 920-1192, Japan.

Abstract

The plastication of pellets in a co-rotating twin-screw extruder is a significant concern for product homogeneity and stability in the plastic industry. We developed a sensing technology for pellet plastication in a plastication and melting zone in a self-wiping co-rotating twin-screw extruder. The collapse of the solid part of the pellets emits an elastic wave as an acoustic emission (AE) that is measured on the kneading section of the twin-screw extruder using homo polypropylene pellets. The recorded power of the AE signal was used as an indicator of the molten volume fraction (MVF) in the range of zero (fully solid) to unity (fully melted). MVF decreased with increasing feed rate monotonically in the range of 2-9 kg/h at a screw rotation speed of 150 rotations per minute (rpm) because of the reduction in the residence time of pellets in the extruder. However, the increase in feed rate from 9 to 23 kg/h at 150 rpm resulted in an increase in the MVF as the friction and compaction of pellets caused their melting. The AE sensor could elucidate the pellet's plastication phenomena caused by friction, compaction of pellets, and melt removal in the twin-screw extruder.

Keywords: acoustic emission; melt removal; pellet plastication; twin-screw extrusion.

Grants and funding

This study was supported by SHIBAURA MACHINE, Japan. Part of the research was supported by a CREST Grant-in Aid (JPMJCR21L3) from the Japan Science and Technology Agency (JST).