The mass melt flow rate parameters were determined using a Zwick Roell Mflow rheometer, in accordance with the ASTM D1238 standard. Prior to testing, the samples were dried under vacuum for 24 hours at 60 °C. Measurements were made under the same conditions for all materials, for a 6 g sample, at a temperature of 125 ⁰C and a load of 2.16 kg. The cut-off time was chosen individually for each of the samples and was in the range of 10-15 s. The MFR index was determined from equation 1.