Effect of carvacrol in the properties of films based on poly (vinyl alcohol) with different molecular characteristics

Poly (vinyl alcohol) (PVA) is a hydrophilic linear polymer obtained from the controlled hydrolysis of poly (vinyl acetate) (PVAc). The molecular weight (Mw) and degree of hydrolysis (DH) of PVA are considered relevant in both the functionality of the polymer and its capacity for film formation. This study analysed the influence of the Mw and DH of PVA on both the film's ability to incorporate carvacrol (CA), for the purposes of obtaining active films for food packaging application, as well as on the film microstructure, thermal behaviour and its functional properties as packaging material. CA was incorporated at 5 and 10 g/100 g polymer by emulsification in the polymer-water solutions, while the films were obtained by casting. The higher Mw polymer provided films with a better mechanical performance but less CA retention and a more heterogeneous structure. In contrast, low Mw, partially acetylated PVA gave rise to homogenous films with a higher CA content that increased the mechanical resistance and stretchability of the films. The melting temperature of this polymer with acetyl groups was lower than the degradation temperature, which makes thermoprocessing feasible. (C) 2020 Elsevier Ltd. All rights reserved.