Melt-Mixing by Novel Pitched-Tip Kneading Disks in a Co-Rotating Twin-Screw Extruder

TL;DR

This paper introduces a novel kneading disk design called pitched-tip kneading disk (ptKD) for twin-screw extruders, analyzing how geometric parameters influence melt-mixing performance through numerical simulations.

Contribution

The study presents a new kneading element design (ptKD) and investigates its mixing characteristics and flow mechanisms using numerical simulations and Lagrangian statistics.

Findings

Different ptKD arrangements exhibit distinct mixing behaviors.

Pitched-tip design effectively balances pressurization and mixing.

Flow coupling effects are key to understanding mixing performance.

Abstract

Melt-mixing in twin-screw extruders is a key process in the development of polymer composites. Quantifying the mixing performance of kneading elements based on their internal physical processes is a challenging problem. We discuss melt-mixing by novel kneading elements called "pitched-tip kneading disk (ptKD)". The disk-stagger angle and tip angle are the main geometric parameters of the ptKDs. We investigated four typical arrangements of the ptKDs, which are forward and backward disk-staggers combined with forward and backward tips. Numerical simulations under a certain feed rate and screw revolution speed were performed, and the mixing process was investigated using Lagrangian statistics. It was found that the four types had different mixing characteristics, and their mixing processes were explained by the coupling effect of drag flow with the disk staggering and pitched-tip and pressure flows, which are controlled by operational conditions. The use of a pitched-tip effectively to controls the balance of the pressurization and mixing ability.