Multilayered Alkyd Resin/Nanocellulose Coatings for Use in Renewable Packaging Solutions with a High Level of Moisture Resistance

Abstract

A surprisingly simple and rapid methodology for large-area, lightweight, and thin laminate coatings with remarkable moisture barrier properties is introduced. Commercially available paperboards are coated with thin layers of nanocellulose. The nanocellulose coating induces a surface smoothening effect on the coated sheets as characterized by environmental scanning electron microscopy and white light interferometry. A moisture-protective layer of renewable alkyd resins is deposited on the nanocellulose precoated sheets using a water-borne dispersion coating process or lithographic printing. Through an auto-oxidation process, the applied alkyd resins are transformed into moisture sealant layers. The moisture barrier properties are characterized in detail by water vapor permeability measurements at different levels of relative humidity. The water vapor barrier properties of the nanocellulose precoated substrates were significantly improved by thin layers of renewable alkyd resins. The effect of the alkyd resin properties, coating technologies, and base paper substrates on the final barrier performance of the sheets were studied. It was found that the nanocellulose coating had a notable effect on the homogeneity and barrier performance of the alkyd resin layers and in particular those alkyd resin layers that were applied by printing. The concept is environmentally friendly, energy-efficient, and economic and is ready for scaling-up via continuous roll-to-roll processes. Large-scale renewable coatings applicable for sustainable packaging solutions are foreseen.

High performance green barriers based on nanocellulose

“…Recently, the water vapor permeability of the paper substrates was substantially decreased with a multilayer coating of nanocellulose and alkyd resins. The WVTR reached very low and reached values considered as high barriers in packaging applications [49].…”

Nanostructured Films Produced from the Bleached Pinus sp. Kraft Pulp

“…Recent research shows that in relation to conventional material, the paper or film produced from nanocellulose presents higher density, flexibility, and mechanical resistance, as well as lower porosity (Balea et al, 2016;Bharimalla et al, 2015;González et al, 2014). Cellulosic nanofiber films have properties considered satisfactory for application in packages, a fact that explains the food industry's increasing interest in replacing packaging made of petroleum-based polymers with biodegradable materials such as paper coated with cellulosic nanofilms (Aulin & Ström, 2013;Herrera et al, 2016;Vandermoere et al, 2011).…”

Nanofibrillated cellulose in wood coatings: mechanical properties of free composite films

“…Many different applications of NFC and nanocellulose reinforced composites were already proposed and investigated, among others for biomedical and packaging applications and for electronic displays [22][23][24]. Using NFC for coating applications was also suggested; however, the main focus has been on paper and packaging coatings, intending improved mechanical, barrier and antimicrobial properties [18,24,25]. To our knowledge, only few reports on using NFC or other nanocelluloses in wood coating applications exist.…”