One-Step Extrusion to Minimize Thermal Decomposition for Processing PLA-Based Composites

One-step extrusion techniques (combining compounding and product extrusion together) have been developed to minimize the decomposition of polyesters during thermal processing. Such treatment is particularly meaningful for the application of biodegradable polyester composites reinforced with the fillers containing moisture or hydroxyl groups, such as cellulose and starch etc. Poly (lactic acid)/starch composites was used as a model system in this work. Two kinds of one-step extrusion systems have been developed through (1) a twin screw extruder connecting with a single extruder, and (2) a twin screw extruder with a single screw zone respectively. The comparison between the one-step and two-step extrusions has been carried out based on their microstructures and performances via characterizations of molecular weight and molecular weight distribution, Fourier transform infrared spectroscopy, as well as tensile and drop impact testing. The results demonstrated that mechanical properties of samples were enhanced with the one-step extrusion preparation, comparing with the two-step processing, particularly in toughness and tensile strength, mainly because the one-step methods reduced the decomposition of polyesters during the thermal processing. It is also expected that the one-step extrusions technology will decrease the processing cost by reducing the amount of utilized energy, and can be used for the processing of other moisture sensitive polyesters.