Examination of Starch Preprocess Drying and Water Absorption of Injection-Molded Starch-Filled Poly(lactic acid) Products

This article focuses on the drying of native maize starch before compounding with poly(lactic acid) (PLA) and on the water absorption of injection-molded starch-filled PLA products. The mass loss of starch was examined while drying in a vented oven at various temperatures, and a proposal was made for complete drying. A temperature-dependent mathematical model was established to describe the moisture loss of native starch. The dried starch was mixed with PLA, compounded with a twin-screw extruder, and finally injection-molded into 80 x 80 mm(2) area, 2-mm-thick flat specimens. These specimens were placed into distilled water to analyze the water uptake and the change in mechanical properties and deformation caused by water uptake for 1 month. Another mathematical model was established to describe the water absorption of the specimens. With the proper drying of starch and PLA, a 30 wt% starch content PLA product was injection-molded with significantly higher tensile strength compared with literature data. POLYM. ENG. SCI., 51:843-850, 2011. (C) 2011 Society of Plastics Engineers