Active Thermoplastic Polyurethane Interfaces for Lipid Feedstock Stabilization: Controlled α-Tocopherol Release and Interfacial Protection of Waste Cooking Oil

Waste cooking oil (WCO) is a highly oxidizable lipid feedstock, whose compositional drift during storage limits downstream valorization. Stabilizing WCO prior to upgrading is crucial to preserve feedstock quality, reduce variability and improve resource-recovery efficiency. In this study, thermoplastic polyurethane (TPU)-based films were fabricated as active interfacial films, by incorporating antioxidant additives to suppress lipid peroxidation through combined barrier and controlled antioxidant delivery mechanisms. Among four tested compounds, that is, quercetin, curcumin, resveratrol, and α-tocopherol (TP), the latter exhibited the highest efficacy in reducing peroxide values due to its strong antioxidant activity and oil solubility. TPU–TP films were produced with 0%–20% loadings and characterized for surface, optical, chemical, thermal, mechanical, wettability, and barrier properties. Spectrophotometric analysis demonstrated enhanced UV blocking properties. Release studies in ethanol 95%, a standard fatty-matrix simulant used here as a medium for lipophilic additive release, revealed a controlled diffusion of TP, which resulted in more than 95% of antioxidant activity. In addition, these films acted as physical barrier to microbial infiltration under the adopted test conditions. Use-case tests showed that TPU-TP20 films significantly preserved the triacylglycerols profile of WCO over 90 days. These findings establish TPU–TP films as active interfacial materials for stabilizing oxidizable lipid streams via coupled interfacial barrier effects and controlled antioxidant delivery.