The melt flow index (MFI) was measured based on the ISO 1133 standard (PN-93/C-89069) using a CAEST type CA-MAN-001 plastometer and the applied load was 2.16 kg. The cut-off time was 30 s. The MFI was calculated according to the formula: MFI = 600 × mt , where 600 stands for the reference time (10 min = 600 s), m stands for the mass of the sample after the desired period (g), and t stands for the period of time (s).