Abstract
The deterioration of the physical–mechanical properties and loss of the chemical safety of plastics after consumption are topics of concern for food packaging applications. Incorporating nanoclays is an alternative to improve the performance of recycled plastics. However, properties and overall migration from polymer/clay nanocomposites to food require to be evaluated case-by-case. This work aimed to investigate the effect of organic modifier types of clays on the structural, thermal and mechanical properties and the overall migration of nanocomposites based on 50/50 virgin and recycled post-consumer polypropylene blend (VPP/RPP) and organoclays for food packaging applications. The clay with the most hydrophobic organic modifier caused higher thermal stability of the nanocomposites and greater intercalation of polypropylene between clay mineral layers but increased the overall migration to a fatty food simulant. This migration value was higher from the 50/50 VPP/RPP film than from VPP. Nonetheless, clays reduced the migration and even more when the clay had greater hydrophilicity because of lower interactions between the nanocomposite and the fatty simulant. Conversely, nanocomposites and VPP/RPP control films exhibited low migration values in the acid and non-acid food simulants. Regarding tensile parameters, elongation at break values of PP film significantly increased with RPP addition, but the incorporation of organoclays reduced its ductility to values closer to the VPP.
Highlights
Polypropylene (PP) is a thermoplastic polymer commonly used to manufacture kitchen utensils, automobile parts, textiles, pipes and packaging
Overall migration studies of recycling and valorization of postconsumer polypropylene (RPP) nanocomposites under three different food simulants were carried out to understand their dependence on the type of packaged food
The highest intercalation grade of PP between clay mineral layers was reached with OCN because its organic modifier is more hydrophobic
Summary
Polypropylene (PP) is a thermoplastic polymer commonly used to manufacture kitchen utensils, automobile parts, textiles, pipes and packaging. Most of the studies on PP/clay nanocomposites have used virgin resin, and only a few works have focused on the reinforcement of RPP where the nanofillers can potentially act as performance improvers of the degraded plastic, which has a molar mass distribution different than VPP, depending on the grade and source of the recycled polymer [5,6,7,8] These scarce studies have only focused on the morphology and some rheological–mechanical aspects and not on the chemical safety and overall migration of the nanocomposites, which is essential for food packaging materials to guarantee human health and consumer acceptability. Advances in this research line are highly required because: (i) little information on the safety of nanocomposite materials is available; (ii) the variation in the RPP properties and the interactions between components of the nanocomposite and foodstuff, as a function of the type of polymer and organic modifier of the nanoclay, need to be addressed; (iii) the growing new developments of nanotechnology-based materials for food packaging [9,10,11,12]
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