Post-consumer Recycled PET Active Films Containing β-Cyclodextrins-Based Inclusion Complexes with Essential Oils: A Comparative Study between Processing Methodologies

Post-consumer PET (rPET) has become a worldwide concern due to the huge waste accumulation. Therefore, it is necessary to explore processing methods to recycle or reuse rPET to save resources and contribute to solving environment-related issues. Furthermore, the addition of inclusion complexes in the rPET matrix increases its application in terms of the release of active compounds that improve the added value of the polymer. Thus, active rPET films with thyme and orange essential oils were prepared by compression molding or extrusion. The effect of the different processing methods, as well as reprocessing, on the structural, mechanical, and antifungal properties of the active films was assessed. The results show that compression molding is not a suitable method to produce active films since their operation conditions, such as residence time and temperature, triggered the decomposition of the inclusion complex (IC), negatively affecting the appearance and mechanical properties (brittle and fragile) of films. Conversely, the extrusion process allowed preserving the IC and dispersing them adequately within the rPET matrix, maintaining the mechanical integrity of the films and resulting in a high antifungal activity against the growth of Penicillium funiculosum hyphae. This behavior was also observed after the re-extrusion process, corroborating that extrusion is a suitable method to process the active rPET films more than once without the detriment of their mechanical and antifungal properties.