Fig. 6: 2D numerical simulation of flow and pressure around growing spherulites and the resulting spherulite elongation.
a–d In the 6 × 1 2D simulation box each spherulite is represented by a circular boundary with a constant inflow rate, located at different positions between the top and bottom boundaries, representing the glass plates. Only the central portion of the box is shown. Red arrows = flow lines, black lines = isobars. a, One spherulite growing close to the top surface. b Two spherulites growing simultaneously at opposite (top and bottom) surfaces. To represent a situation where the top spherulite nucleated earlier and is larger, hence consuming more molten polymer, its inflow rate is three times that of the bottom spherulite. c One spherulite grows in the middle of the cell. d One spherulite approaches the top surface. The negative pressure between surfaces of the substrate and the spherulite increases as their distance d decreases; this is particularly clear above the spherulite in (d). e Aspect ratio of spherulite of dye-labeled neat PLA vs. distance from the nearest glass surface for different sample thicknesses; empty symbols = experimental, red balloons = average. As indicated by the inset, DV and DH are diameters along z and in xy plane, respectively. Error bars correspond to standard deviation.
