Silane doped biodegradable starch-PLA bilayer films for food packaging applications: Mechanical, thermal, barrier and biodegradability properties

Abstract

In this work, pure potato starch (PPS) purified from waste potato starch, was recovered and used. PPS was modified by 3-APTMS (3-(aminopropyl) trimethoxy silane) to manufacture a crosslinked film. To obtain a bilayer PPS-3APTMS-PLA film, the polylactic acid (PLA) was employed with PPS-3APTMS by casting method. The resulting materials, PPS-3APTMS and PPS-3APTMS-PLA were characterized by attenuated total reflectance fourier transform ınfrared (ATR-FTIR), x-ray Diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA). The silane-doped bilayer films have more thermal stability compared to PPS. The mechanical, solubility, swelling, water vapor permeability, optical properties and biodegradability under controlled compost conditions were examined. When the tensile strength of the PPS, PPS-3APTMS and PPS-3APTMS-PLA films were evaluated, the tensile strength (TS) were to 1.017±0.35 MPa, 1.437 ± 0.19 MPa and 10.918 ± 1.30 MPa, respectively. The PPS and PPS-3APTMS films were not elongation at break, while it was found about 21.94 ± 9.48 for the bilayer PPS-3APTMS-PLA film. The solubility, swelling, water vapor permeability, and transparency decreased for bilayer films. The water vapor permeability of PPS, PPS-3APTMS and PPS-3APTMS-PLA films were obtained as 31.69±0.4 × 10−7 g s−1 m−1 Pa−1, 28.96±0.4 × 10−7 g s−1 m−1 Pa−1, and 14.26±0.3 × 10−7 g s−1 m−1 Pa−1, respectively. Then, the biodegradability of films was performed under controlled compost conditions for 46 days according to ISO-14,855 standard. The biodegradation of PPS, PPS-3APTMS and PPS-3APTMS-PLA was also calculated as 9.30%, 5.45% and 5.08%. Biodegradation of PPS-3APTMS film decreases compared to PPS. Furthermore, the biodegradation value of bilayer film, PPS-3APTMS-PLA, was also decreased due to the slower degradation tendency of PLA. The contribution to the reusability of waste starch and the modifying of starch for food packaging and coating applications are the novelty aspects of the current study.