PPF melt viscosity vs. (a) T, (b) T-Tg, and (c) Tg/T. Inset in (a): viscosities at various temperatures reduced to 40 °C vs. temperature. Inset in (b): viscosities at various temperatures vertically shifted to the data for PPF1 vs. T-Tg by shift factors of 0.582, 0.275, 0.160, and 0.064 for PPF2, 3, 4, and 5–7, respectively. Inset in (c): viscosities at various temperatures vertically shifted to the data for PPF1 vs. Tg/T by shift factors of 0.574, 0.329, 0.197, 0.119, and 0.079 for PPF2, 3, 4, 5, and 6–7, respectively.