Production of biodegradable packaging film based on PLA/starch: optimization via response surface methodology

Today, economic consumption of biodegradable polymers is significant in many applications. Thermoplastic starch (TPS) and polylactic acid (PLA) are two bio-based and biodegradable polymers that are increasingly being used to replace the petrochemical-based polymers. Adding TPS into a PLA matrix can also decrease material cost and increase its biodegradation rate. This work tested the printability of TPS/PLA films. For this purpose, TPS was first prepared by the addition of sorbitol and glycerol as softeners using an internal mixer at 140 degrees C. Then, it was added to the PLA in internal mixer at 180 degrees C. To analyse the data, design of the experiment was done according to Box-Behnken design (BBD) method for three variables in three levels by using Design-Expert software, which led to the preparation of 15 samples. Individual and interactive effects of wt% of PLA in TPS/PLA mixture, the wt% of starch in TPS, and the ratio of sorbitol to glycerol on the tensile properties, thermal properties and printing properties (optical density) were investigated. Solvent-based flexographic ink was applied to test printability of the films. It has been found that the PLA can be successfully printed with flexographic solvent inks to achieve a quality comparable to that of common packaging films.