Desenvolvimento de Nanoblendas PLA/EVOH biodegradáveis com características de barreira a gases e vapores

Abstract

Poly (lactic acid) (PLA) is a non-toxic, transparent and biodegradable aliphatic polyester, produced from renewable raw materials. This polymer meets several requirements for packaging applications, but is fragile and has lower gas and water vapor barrier properties, compared to polymers currently used in this application. The formation of PLA blends with poly (ethylene-co-vinyl alcohol) (EVOH), which has transparency and good gas barrier properties, is an advantageous alternative to modify this biodegradable polymer, in order to obtain better mechanical and barrier properties without loss of transparency. This research objective was to develop biodegradable PLA/EVOH nanoblends, for packaging application, through reactive extrusion followed by the production of films. EVOH was added in 3, 5 and 10 wt%. Two compatibilization systems, containing epoxy as the reactive group, and a catalyst of the reaction between epoxy and hydroxyl, were used for interfacial modification. The influence of the dispersed phase content, the use of different compatibilizers and the presence of the catalyst in the thermal, mechanical, rheological, optical and barrier properties, as well as the the morphology of the blends, were analyzed. It was possible to observe a reduction in the diameter of the dispersed EVOH particles in the PLA matrix through reactive extrusion and addition of compatibilizing systems. The reduction was even more significant with the use of the catalyst, reaching values very close to the nanometric scale, but resulted in the degradation of the PLA matrix. The blends compatibilized with GMA and peroxide presented the best mechanical performance, however still very close to the PLA matrix. The barrier properties of all blends were higher than those of PLA. The blends showed transparency when the film is positioned close to the object, thus presenting sufficient optical property for packaging application.