Effect of processing temperature profile during melt extrusion on thermoplastic starch production

Abstract

This work aims to evaluate the influence of the processing temperature on thermoplastic starch (TPS) for scalable production at the industrial level. Thus, it analyses the impact of six different extruding temperature profiles to plasticize native starch with water as well as with glycerol to obtain thermoplastic starch (TPS) produced by melt-extrusion. The temperature profiles ranged from 70 to 150 ºC. At temperature profiles below 100 ºC, the extrusion conditions were insufficient to disrupt the starch granules completely. Therefore, the material did not plasticize correctly, and the starchy matrix plasticizes partially using a temperature profile of 100 ºC. The water evaporation process affects the final material's microstructure. At temperature profiles above 100 ºC (i.e., 110 and 130ºC), the extrusion conditions allowed the disruption of the starch granule as well as a good material plasticization to obtain TPS. Although TPS obtained with a temperature profile of 150 ºC displayed the highest mechanical properties, the material shows signs of thermal degradation under these conditions. Therefore, TPS processed at a profile with a maximum temperature of 130 ºC showed a higher plasticization effect, good thermal and mechanical properties, and good water uptake capability. With its potential for successful industrial production, TPS can be obtained by processing native starch with water and glycerol at low share rates of 20 rpm and using 130ºC as a maximum processing temperature, offering a range of benefits.