Abstract
In this work, the modification process of poly(lactic acid) (PLA) with metal-based nanoparticle (NPs) additives (Ag, ZnO, TiO2) at different loading (0.5, 1.0, and 2.5 wt%) and by melt-mix extrusion method followed by film formation as one of the advantageous techniques for industrial application have been investigated. PLA nanoparticle composite films (PLA-NPs) of PLA-Ag, PLA-ZnO, PLA-TiO2 were fabricated, allowing convenient dispersion of NPs within the PLA matrix to further pursue the challenge of investigating the surface properties of PLA-NPs reinforced plastics (as films) for the final functional properties, such as antimicrobial activity and surface mechanical properties. The main objective was to clarify how the addition of NPs to the PLA during the melt extrusion process affects the chemistry, morphology, and wettability of the surface and its further influence on the antibacterial efficiency and mechanical properties of the PLA-NPs. Therefore, the effect of Ag, ZnO, and TiO2 NPs incorporation on the morphology (SEM), elemental mapping analysis (SEM-EDX), roughness, surface free energy (SFE) of PLA-NPs measured by goniometry and calculated by OWRK (Owens, Wendt, Rabel, and Kaelble) model was evaluated and correlated with the final functional properties such as antimicrobial activity and surface mechanical properties. The developed PLA-metal-based nanocomposites, with improved mechanical and antimicrobial surface properties, could be used as sustainable and biodegradable materials, offering desirable multifunctionalities not only for food packaging but also for cosmetics and hygiene products, as well as for broader plastic products where antimicrobial activity is desirable.
Highlights
The development of plastic packaging materials is an extremely interesting area of research that has shown rapid growth in recent years
Several studies have been highlighted of poly(lactic acid) (PLA) metal-based NPs composites films; silver (Ag) NPs composites, zinc oxide (ZnO) NPs composites, and titanium dioxide (TiO2) NPs composite films prepared by methods such as in-situ polymerization, solvent casting, electrospinning, extrusion process, which improved good thermal properties and noticeable tensile strength depending on the surface modification of the fillers [34,43,44,45,46] and exceeded antibacterial properties [47,48,49]
Our research focused on the surface properties of PLANPs composite films reinforced with Ag, ZnO, and TiO2 NPs and fabricated by melt-mix extrusion process
Summary
The development of plastic packaging materials is an extremely interesting area of research that has shown rapid growth in recent years. The focus is on the improvement of materials, which, on the one hand, protect the product and extend its life, and on the other hand, have a biodegradable and functional aspect In this regard, petroleum-based plastics such as polyethylene (PE), polypropylene (PP), polyamide (PA) have experienced exponential growth every year due to their easy availability, low cost, good barrier, and mechanical properties for packaging. I.e., Ag, ZnO, TiO2, NPs have an important effect on the cold crystallization kinetics, thermal degradation, semi-crystalline morphology, and segmental dynamics of PLA-NPs composites studied by our previous research [36,50], the exact mechanism for their involvement and the distribution in the surface and their dependency on surface properties of PLA-NPs composites is not fully understood It is the surface or the outermost layer of atoms/molecules of solid that really outlines how the material interacts with its environment and how it behaves for its envisioned purpose. Understanding surface phenomena is crucial, and a deeper understanding of surface parameters’ influence on final functionality can enable its reverse manipulation for material optimization
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