Modelization of flow electrification in a polymer melt

TL;DR

This paper develops a new model for flow electrification in non-Newtonian polymer melts, highlighting the importance of velocity profile shape and slip velocity at the wall, which can be inferred from electrification measurements.

Contribution

It introduces a novel approach to model flow electrification in polymer melts, emphasizing the role of velocity profile shape and slip velocity, unlike previous models based on Newtonian liquids.

Findings

Velocity profile shape significantly affects electrification.

Slip velocity at the polymer/die interface influences electrification.

Electrification measurements can be used to estimate slip velocity.

Abstract

Flow electrification of polymer melts is an important side effect of polymer processing. The studies dealing with this phenomenon are seldom and most of the scientific work has been focused on flow electrification of aqueous and insulating Newtonian liquids. From that prior art it is well established that the flow electrification in Newtonian liquids is a consequence of the formation of an ionic double layer. Convection of this layer induces the electrification of the liquid at the outlet of the pipe. In those models, the key parameters governing the flow electrification are thus the intrinsic electrical properties of the polymer and the flow characteristics. In this work, we reconsider the assumptions made previously and we propose a new approach to modelise the flow electrification in the particular case of non-Newtonian polymer materials in laminar flow conditions. We establish that, a key parameter for the electrification quantification in the polymer melt is the shape of the velocity profile. Additionally, in some cases, we show that a slip velocity at the polymer/die wall interface must be considered to describe accurately the electrification. As a consequence, we deduce that the slip velocity at the interface can be calculated by measuring the electrification: this work gives an alternative manner to measure the slip velocity during polymer flow.