Controlling plasticizer migration based on crystal structure and micromorphology in propionylated starch-based food packaging nanocomposites

Migration of additives is an important issue for proper application in food packaging. In this work, propionylated waxy and normal starch-based nanocomposites (PW-N and PN-N) with two different amylopectin content were immersed in distilled water, and structural changes and migration mechanism of plasticizer (triacetin) were discussed in detail. Results showed that when immersion time was prolonged to 150 h, small crystals of PN-N disappeared, and amorphous structures formed gradually in PW-N and PN-N. Exfoliated structures still remained in PW-N with prolonged immersion time, while exfoliated structures gradually formed from intercalated ones in PN-N, and the peak representing d001 (d-spacing) at q = 1.70 nm^-1 faded. The migration mechanism of triacetin obeyed the first-order kinetic model and Fick's law; furthermore, in comparison with PW-N, PN-N showed a larger diffusion coefficient (D₂ = 12.13 μm²·h^-1). These results contributed to expanding the application of starch-based nanocomposites in future environmentally friendly food packaging.