Development of Biodegradable Films of Cassava Starch and Poly (Butylene Adipate Co-Terephthalate): Effects of Oregano Essential Oil and Potassium Sorbate in Films Characterization

Abstract

Four samples of thermoplastic starch (STP) and poly (butylene adipate co-terephthalate) (PBAT) films added with the preservatives oregano essential oil (OEO) and potassium sorbate (PS), were prepared from the extrusion blow moulding technique in order to evaluate the mechanical properties, water vapour permeability (WVP) and microstructural characteristics so as to develop active films with antimicrobial activity. The samples FC (film without preservative) and F1 (1% OEO) showed higher water sorption than the samples F2 (0.5% OEO and 2.5% PS) and F3 (5% PS) essentially in relative humidity (RH) higher than the 60%. Samples water vapour permeability containing OEO and PS, showed no significant difference from FC. However, the presence of OEO in samples F1 and F3 decreased the solubility coefficient (ß) in 99.5% and 93.8% respectively, compared to FC. The presence of PS in sample F2 increased the diffusion coefficient (Dw) in 4.7 times related to sample FC, so the presence of small molecule PS gave higher porosity to the film. The sample F1 showed an increase in tension at rupture (TR), elongation (E) and elastic modulus (EM) when compared to FC, while F2 and F3 samples revealed a reduction in TR and EM, and increased E. From Scanning Electronic Microscopy, it was possible to observe greater uniformity in FC and F1 compared to F2 and F3 samples. Thus, OEO presence contributes to improve the polymer mechanical properties and the increased homogenization. As well as, the presence of PS contributed to the film higher elasticity, less resistance and less homogeneity. Therefore, the presence of OEO in STP and PBAT films gives the best feature for the development of active films related to the mechanical properties, microstructural and of barriers.