*2.3. Lab-Scale and Semi-Industrial Scale-Up Extrusion Compounding and Injection Molding*

PLA based composites containing different HSP amounts (from 20 up to 40 wt.%) were extruded at laboratory scale with a Haake Minilab II (HAAKE, Vreden, Germany) twin-screw mini-compounder. Before the extrusion, all materials were dried in a Piovan DP 604–615 dryers (Piova S.p.A., Verona, Italy) at 60 ◦C for 16 h. The extrusion temperature was set at 190 ◦C with a mixing residence time inside the extrusion chamber of 40 s and a screw speed of 60 rpm. The strand coming out from the mini extruder was then cooled and pelletized to obtain granules. The composites name and their compositions are reported in Table 1.


**Table 1.** Blends name and compositions.

\* Blends extruded with a semi-industrial COMAC twin-screw extruder (up-scaled).

To the best composition of both HSP typologies, the extrusion compounding was scale-upped on a semi-industrial Comac EBC 25HT (L/D = 44) (Comac, Cerro Maggiore, Italy), twin screw extruder. Also, in this case, the materials were dried following the same procedure adopted for the mini-compounding. PLA pellets were introduced into the main feeder while HSPs were fed with a specific lateral feeder that allows, once that the weight concentration was set, a constant feeding rate during the extrusion. A schematization of the extrusion feeder configurations, as well as the temperature profile adopted in the 11 extruder zones, is reported in Figure 1.

**Figure 1.** Schematization of the semi-industrial Comac twin screw extruder. In the figure are highlighted the feeder position, the screw configuration and the profile temperature along the 11 extruder zones.

The strands coming out from the extruder were cooled in a water bath and then pelletized by an automatic cutter. After the extrusion (both in lab-scale and in scaleup process), the pellets (dried in the before mentioned Piovan dryer at 60 ◦C for 16 h) were injection molded with a Megatech H10/18 injection molding machine (TECNICA DUEBI s.r.l., Fabriano, Italy) to obtain ISO 527-1A dog-bone specimens (width 10 mm, thickness 4 mm, useful length 80 mm) and ISO 179 Charpy impact specimens (width 10 mm, thickness 4 mm, length 80 mm). The injection molding was carried out in order to minimize any change in the processing parameters (reported in Table 2) for a better understanding of melt viscosity variation induced by the addition of different quantities and different HSP typology (H0210 and HM200). Consequently, the temperature profile, the mold temperature, the injection time, and the cooling time were fixed and only the injection pressure was modified when necessary.



\* Blends extruded with a semi-industrial COMAC twin-screw extruder (up-scaled).
