Abstract
One of the most promising expectations in the design of new materials for food packaging is focused on the development of biodegradable systems with improved barrier character. In this sense PLA reinforced with nanoclay is a potential alternative to the use of conventional oil-derivative polymers due to the synergetic effect of the biodegradable character of PLA and the barrier-induced effect derived from the dispersion of nanoparticles. In this work, composite materials based on PLA and reinforced with bentonite nanoparticles (up to 4% w/w) (NC) have been prepared to produce films with improved barrier character against water vapor transportation. Additionally, the biodegradable character of the composites depending on the crystallinity of the polymer and percentage of NC have been evaluated in the presence of an enzymatic active medium (proteinase K). Finally, a study of the capacity to film production of the composites has been performed to determine the viability of the proposals. The dispersion of the nanoparticles induced a tortuous pathway of water vapor crossing, reducing this diffusion by more than 22%. Moreover, the nanoclays materials were in all the cases acceptable for food packing in terms of migration. A migration lower than 1 mg/m2 was obtained in all the materials. Nonetheless, the presence of the nanoclays in decreased biodegradable capacity was observed. The time was enlarged to more than 15 days for the maximum content (4% w/w). On the other hand, the incorporation of NC does not avoid the processability of the material to obtain film-shaped processed materials.
Highlights
Some polymeric materials, depending on the chemical stability and the additives, are suitable to be in contact with foods, as it is clear from the European Regulation (EC) No 1935/2004
In this sense PLA reinforced with nanoclay is a potential alternative to the use of conventional oil-derivative polymers due to the synergetic effect of the biodegradable character of PLA and the barrier-induced effect derived from the dispersion of nanoparticles
The best results have been obtained for composites based on starch reinforced with polar nanoclays [35] or even another kind of nanostructured reinforcement, such as nanofibrillated cellulose [36], where the incorporation of 0.36 wt% of this natural reinforcement to plasticized starch produced a decrease in water vapor transmission rate by 56% and 46% in the case of oxygen permeability
Summary
Some polymeric materials, depending on the chemical stability and the additives, are suitable to be in contact with foods, as it is clear from the European Regulation (EC) No 1935/2004. These nanocomposites have been found materials with improved barrier character against water vapor and oxygen transmission depending on the kind of nanoreinforcement added to the matrix [33,34] In this sense, the best results have been obtained for composites based on starch reinforced with polar nanoclays [35] or even another kind of nanostructured reinforcement, such as nanofibrillated cellulose [36], where the incorporation of 0.36 wt% of this natural reinforcement to plasticized starch produced a decrease in water vapor transmission rate by 56% and 46% in the case of oxygen permeability. It made interesting the study of such materials in a film product and the behavior in the biodegradation
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