Internal Seminar: Claire McIlroy

[Industrial and Applied Mathematics Seminar]

Claire McIlroy

University of Nottingham

Modelling Extrusion-Based Printing of Entangled Polymers

The most common method for printing plastics (polymer melts) is known as fused filament fabrication (FFF). This process involves melting a thermoplastic, followed by layer-by-layer extrusion, cooling and re-solidification. The main concern with FFF is the strength at the welds between printed layers; bulk strength is never achieved in these regions and the reason is currently unclear. We use a molecularly-aware non-isothermal model of the polymer melt to predict how high-shear rates during the deposition process can stretch and align polymer molecules with the flow direction. For amorphous melts, we attribute reduced weld strength to a partially disentangled structure at the onset of the glass transition. For semi-crystalline melts, we explore how the stretch induced by the printing flow can enhance nucleation and lead to a gradient in the number of nuclei across a printed layer.