Development and characterization of biodegradable bilayer packaging films based on corn starch-polylactic acid as raw material

This study aimed to develop corn starch (CS) and polylactic acid (PLA) degradable bilayer films without the addition of compatibilizers or plasticizers. Different ratios of CS-PLA bilayers were prepared, and considering the performance and economic benefits of the films, it was concluded that the best overall performance of the bilayers was obtained for a CS: PLA ratio of 50:50. At this time, the bilayer has the best adaptability to elongation at break (168%) and tensile strength (17.2 MPa), and its transparency is close to that of ordinary plastic packaging, allowing visual observation of the state of the food inside the film package. At this ratio, the films have some ability to block UV light and protect the food from oxidation processes or other UV-induced adverse reactions. Its water vapor permeability (0.962 x 10- 12 gd- 1 m- 1 Pa- 1), water absorption (43.4%), and oxygen permeability (2.42 x 10- 11 cm2s- 1p.a.- 1) were all at suitable levels. Scanning electron microscope (SEM) cross-sectional images and Fourier transform infrared (FTIR) spectra of the bilayer membranes showed that there was a physical connection between the two membranes, but there was no gap, indicating that the two membranes were well bonded. X-ray diffraction (XRD) showed that the films had the characteristics of a semi-crystalline polymer with low crystallinity. A 10-week degradation experiment yielded good degradability of the bilayer film. These results show that combining PLA and CS to produce double-layer films has great potential to compensate for each other's deficiencies and improve the suitability of both for food packaging alone.