Cassava starch and glycerol were weighed, premixed, and fed into a feeder manually; the extrudates were then introduced to an injection molder to form disc and dumbbell specimens. With the barrel temperature profiles of 100/110/115°C, the lengths of time of 30 to 60 s, and the injection conditions of 110 to 120°C at the highest pressure (150 psi),
the processability of TPCS depended on the glycerol content. The results are shown in Table 3.1. With the highest glycerol content (50%), TPCS specimens were the clearest, most flexible and processable, but most shrinkable. With low glycerol content (≤ 20%), TPCS extrudates were stiff, which made it difficult to process in an injection molder. The smallest amount of glycerol (10%) was not effective enough to disrupt intermolecular bonds of starch and generate thermoplastic material. Increasing extrusion temperature to around 130-150°C did not improve the processability of starch but enhanced its thermal degradation.