Abstract
The use of paper as a sustainable packaging material is favored, but it lacks sufficient barrier properties in terms of water repellence and oil resistance. Novel approaches consider active packaging materials or coatings with controlled release providing additional functionality for delivery of specific components to the surface. In this study, the development of a waterborne coating with organic nanoparticles and encapsulated sunflower oils is presented as a system for thermal release of the oil and on-demand tuning of the final barrier properties of the paper substrate. After synthesis of the nanoparticles, it seems that the encapsulation of various grades of sunflower oil (i.e., either poly-unsaturated or mono-unsaturated) strongly affects the encapsulation efficiency and thermal release profiles. The water contact angles are controlled by the oil release and chemical surface composition of the coating upon thermal heating. The oil resistance of the paper improves as a more continuous oil film is formed during thermal release. In particular, the chemical surface composition of the paper coatings is detailed by means of micro-Raman spectroscopy and surface imaging, which provide an analytical quantification tool to evaluate surface coverage, oil delivery, and variations in organic coating moieties.
Highlights
Today, the packaging industry has urgency for more sustainable solutions and new packaging concepts [1], combining both a rational selection of materials and the introduction of additional functionalities
Whereas packaging coatings were historically seen as an inert barrier layer [4], novel research into active packaging coatings considers the interaction with the environment in order to optimize preservation [5,6]
The cross sections confirm that the coatings are positioned on top top of of the the paper paper substrates, substrates,with withaacoating coatingthickness thicknessofofabout about5 5μm
Summary
The packaging industry has urgency for more sustainable solutions and new packaging concepts [1], combining both a rational selection of materials and the introduction of additional functionalities. Controlled release packaging (CRP) has been introduced as a novel generation of packaging materials [7,8,9], which provide active release of compounds over time or depending on their environment at desirable rates. A primary concern for paper-based packaging is to improve its barrier properties; in particular, the water repellence needs to be controlled [12]. The protection of paper-based packaging is ensured through additional coating layers and is often done industrially through lamination with a polymer [13]. The lamination reduces the paper recyclability, and alternative methods based on hydrophobic dispersion coatings have been developed [14,15,16]. The hydrophobicity of cellulose is introduced by direct chemical modification through grafting [17,18], or with coating deposition of silylated soybean oil [19] or silicone oil [20]
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