Independent variable Coded levels -1.682 -1 0 1 +1.682 Barrel exit temperature (°C) 76.3 90 110 130 143.6 Screw speed (rpm) 59.6 80 110 140 160.5 Feed rate (kg/h) 26.4 40 60 80 93.6

Table 1: Coded and actual levels of independent variables used for optimization of single-screw processing conditions as determined by the central composite design (CCD).