Sustainable, Fluorine-Free, Low Cost and Easily Processable Materials for Hydrophobic Coatings on Flexible Plastic Substrates.

Carmela T Prontera,Maria Montanino,Paolo Tassini,Paola Manini,Maria G Maglione,Carla Minarini,Giuliano Sico,Anna De Girolamo Del Mauro

doi:10.3390/ma12142234

Abstract

Zinc oxide nanoparticles (ZnONPs) and stearic acid are herein used for the preparation of hydrophobic coatings with good moisture barrier property on flexible plastic substrates. Fast, high throughput, mild and easy-to-run processing techniques, like airbrushing and gravure printing, are applied for thin films deposition of these materials. The results of this study indicated that the best hydrophobic coating in terms of water contact angle (115°) is obtained through a two-steps printing deposition of a ZnONPs layer followed by a stearic acid layer. All the deposition procedures proved to be effective in terms of water vapor barrier properties, reaching values of 0.89 g/m2/day, with a 45% reduction with respect to the bare substrate. These preliminary data are very encouraging in the perspective of a low cost and green approach for the realization of functional coatings for packaging applications.

Highlights

Hydrophobic surfaces have attracted much interest in the last decades for their applications in daily life as well as in some industrial processes
It is still a challenge to develop simple, fast, low-cost, environment-friendly routes for hydrophobic surfaces with controllable morphology to broaden their industrial applications [12,19,20]. To overcome this gap and fulfill the green requisites, we report on the preparation of hydrophobic coatings based on the deposition of bio-compatible zinc oxide nanoparticles (ZnONPs) functionalized with stearic acid on flexible polyethylene naphthalate (PEN) substrates
The deposition of the Zinc oxide nanoparticles (ZnONPs)/stearic acid coatings has been performed by the gravure printing technique following a previously reported protocol [30] and by the airbrushing technique

Summary

Introduction

Hydrophobic surfaces have attracted much interest in the last decades for their applications in daily life as well as in some industrial processes. The hydrophobicity of a surface is strongly influenced by its composition [8] and by texturing and roughness [9,10] In this sense, many strategies have been developed to increase the water contact angle (WCA) of the surfaces, such as the deposition of layers of various materials (i.e., fluorine or hydrocarbon compounds [11,12], some types of wax [13] or organic and inorganic materials showing low surface energy [14,15]). Prompted by the search for more sustainable processes and products (most of hydrophobic surfaces are obtained by treatments with fluorine compounds which cause harmful effects to the environment due to their bioaccumulation [17]), particular attention has been paid to the design of bionic surfaces inspired to the natural model of the super-hydrophobicity: the lotus leaf [18]

Methods

Discussion

Conclusion