2.3. Viscosity measurements
The melt-viscosity of all the materials under processing conditions was measured using a high pressure capillary rheometer Rheograph 2002 (Göttfert) with a capillary die of 1 mm diameter and a L/D ratio of 30. Measurements were performed at 260 °C over a shear rate range, γ, between 10 and 300 s−1. Measurements for the Bagley correction have been performed with capillary dies having a L/D ratio of 30/1, 20/1 and 10/1. For the shear rate used to calculate the viscosity ratios (γ=80 s−1), the Rabinowitch correction factor was negligible for the lower viscosity materials and became more important for the more viscous materials.