Bilayer biodegradable films prepared by co-extrusion film blowing: Mechanical performance, release kinetics of an antimicrobial agent and hydrolytic degradation

Bilayer biodegradable, eco-friendly films were prepared by co-extrusion film blowing, coupling polylactic acid (PLA) and Bio-flex ® (BIO). Furthermore, in the PLA layer, carvacrol (CRV) was added as a natural antimicrobial additive, whereas a nanoclay (D72T) was integrated to protect CRV from volatilization and to modulate release. The materials were analyzed by morphological, chemical-physical, mechanical testing. Furthermore, CRV release and degradation tests were performed. The results pointed out that coupling the two matrices allows gathering the stiffness of PLA with the ductility of BIO. Furthermore, the interlayer adhesion is promoted by CRV. D72T exerts a key-role in avoiding CRV volatilization, thus allowing more prolonged release. Degradation tests results highlight that bilayer films, while being particularly resistant in both acidic and neutral environments, showed a rapid degradation under alkaline conditions, which proved to be intermediate between those of the corresponding monolayers.