Claire McIlroy's paper on a realistic calculation of polymer structure and the entanglement state has been published. port has now been published in Journal of Rheology.
"Three-dimensional (3D) printing is rapidly becoming an effective means of prototyping and creating custom consumer goods. The most common method for printing a polymer melt is fused filament fabrication (FFF) and involves extrusion of a thermoplastic material through a heated nozzle; the material is then built up layer-by-layer to fabricate a 3D object. Under typical printing conditions, the melt experiences high strain rates within the FFF nozzle, which are able to significantly stretch and orient the polymer molecules. In this paper, we model the deformation of an amorphous polymer melt during the extrusion process, where the fluid must make a 90 turn. The melt is described by a modified version of the Rolie–Poly model, which allows for flow-induced changes in the entanglement density. The complex polymer config- urations in the cross section of a printed layer are quantified and visualized. The deposition process involving the corner flow geometry dominates the deformation and significantly disentangles the melt."