Mistura polimérica de poli(ácido lático)/poli(etileno-co-acetato de vinila) com incorporação de polietilenoglicol e quitosana como agentes modificadores de propriedades

Abstract

Poly (lactic acid) (PLA) has been employed in the packaging area, however, in order to improve its processing features and tenacity. Polymer blends of PLA with poly(ethylene-co-vinyl-acetate) (EVA), polyethylene glycol (PEG) and chitosan (QUI) were developed by extrusion and injection process while films were obtained by compression on this work. Morphological, thermal and mechanical properties of PLA blends have been investigated and films have been developed and put in contact with a nutritional product, the loaf bread, analyzing then its antimicrobial properties, humidity, water activity, texture and color and on the minimally processed apple, analyzing then its antimicrobial properties, antioxidant activity, polyphenols, texture, pH, soluble solids as well as color. The PLA/EVA/PEG and PLA/EVA/PEG/QUI blends when compared to PLA, showed partial miscibility, reduction of glass transition temperature (Tg), lower flexural strength and of the modulus of elasticity, evidencing then a reduction in molecular hardness and an increase in the deformation ability of the polymer, properties of interest to process PLA and for packaging manufacture. The exposure to a nutritional product, the loaf bread, to the poly blends with chitosan promoted an inhibitory effect in the growing of molds and yeasts of around 50% (with poly blend containing 5 phr of chitosan when compared to chitosan-free blend), without affecting the humidity levels, water activity and texture of product, supporting the maintenance of the color during its storage. The contact of films with chitosan on minimally processed apples have promoted a decrease in the growing of molds and yeast of around 54% (with poly blends containing 5 phr of chitosan when it was compared to chitosan-free bled), without affecting the soluble solids levels, pH, texture and weight loss. It has contributed also to avoid the enzymatic browning and increased the total polyphenols levels by 20% and triplicated the antioxidant activity recorded after 10 days of storing the fruits that had been in contact with the poly blends PLA/EVA/PEG/QUI. Finally, it can be concluded that EVA/PEG and chitosan blends added to PLA have allowed modifications on the hardness and processability properties and that the application of chitosan proved to be an efficient action antimicrobial and antioxidant allowing the results obtained here and purpose of this study.