Extrusion parameters to produce a PLA-starch derived thermoplastic polymer

The purpose of this study was to develop a biodegradable thermoplastic polymer based on starch and polylactic acid (PLA) blends with mechanical properties adequate for a wide range of applications. A thermoplastic starch (TPS) was formulated using native corn starch, glycerol as a plasticizer ranging from 30 to 50% (w/w) and citric acid (1.0%, w/w) as a crosslinker. The TPS was mixed with polylactic acid (PLA) [0-50%, w/w]. The material was prepared by extrusion using a single screw extruder. The variables for the experiment design were PLA concentration, extrusion temperature, glycerol concentration and velocity of the screw. Samples before and after extrusion were characterized by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DCS), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction. We evaluated the mechanical Young's modulus, tensile strength and elongation at break. All treatments were performed according to the experiment design. The results of the characterization of the material were analyzed using the response surface methodology (RSM). The RSM revealed the optimum PLA concentration, extrusion temperature, and screw velocity that would produce a corn starch-PLA biodegradable plastic with mechanical properties closer to those of the petroleum-derived plastics.