Evaluation of Layer Adhesion and Uniformity in Poly(lactic acid) and Thermoplastic Starch Multilayered Films

Abstract

Multilayered films of poly(lactic acid) (PLA) and thermoplastic starch (TPS) offer complementary characteristics that are promising for sustainable packaging applications. In this study, an in-house designed three-line coextrusion process was developed to fabricate layered films. These films were produced at varying shear rates and viscosity ratios with and without compatibilizers. Rheological and thermal analyses were used to investigate adhesion strength and uniformity. Results showed the processing shear rate has a significant effect up to 136% on adhesion strength, its maximum at 10.6 s–1. Viscosity ratio, varied by plasticizer content in TPS, impacted adhesion strength up to 48% within the studied ranges, showing its maximum at 25 wt % added plasticizers. Results showed that 2.5 wt % of compatibilizer, maleic anhydride, within TPS increased adhesion strength up to 35%. Thermal analysis of layers at different locations along the cross-section revealed that the viscosity ratio had a defining impact on layer uniformity of TPS within PLA layers. This study highlights the importance of material and processing parameters in designing a biobased sustainable packaging solution.