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Beeswax is a bio-sourced, renewable, and even edible material that stands as a convincing option to provide paper-based food packaging with moisture resistance. Nonetheless, the difficulty of dispersing it in water limits its applicability. This work uses oxidized, negatively charged cellulose nanofibers along with glycerol to stabilize beeswax-in-water emulsions above the melting point of the wax. The synergistic effects of nanocellulose and glycerol granted the stability of the dispersion even when it cooled down, but only if the concentration of nanofibers was high enough. This required concentration (0.6–0.9 wt%) depended on the degree of oxidation of the cellulose nanofibers. Rheological hindrance was essential to prevent the buoyancy of beeswax particles, while the presence of glycerol prevented excessive aggregation. The mixtures had yield stress and showed pseudoplastic behavior at a high enough shear rate, with their apparent viscosity being positively influenced by the surface charge density of the nanofibers. When applied to packaging paper, the nanocellulose-stabilized beeswax suspensions not only enhanced its barrier properties towards liquid water (reaching a contact angle of 96°) and water vapor (<100 g m−2 d−1), but also to grease (Kit rating: 5) and airflow (>1400 Gurley s). While falling short of polyethylene-coated paper, this overall improvement, attained using only one layer of a biobased coating suspension, should be understood as a step towards replacing synthetic waxes and plastic laminates. [ABSTRACT FROM AUTHOR]

Featured Application: An improvement in adhesion (gluing) in the printing production process. In this study, the effect of air plasma on the surface properties of printed and coated cardboard was investigated. The material was activated by low-pressure cold plasma for 1, 10, 20, and 30 s. Wettability changes on the surface were examined by contact angle measurements using the sessile droplet technique. The differences in the surface free energy were calculated using the Lifshitz–van der Waals/acid–base and Contact Angle Hysteresis approaches. Optical profilometry was used for the surface roughness evaluation and an X-ray photoelectron spectroscopy analysis was performed to find changes in surface chemistry. Adhesive strength tests were carried out to estimate the adhesion changes after the material's modification. It was found that the water and formamide contact angles increased after the plasma treatment while the diiodomethane contact angle did not change. As a result of the modification, the surface free energy also increased significantly and the surface roughness increased. The pull-off tests confirmed the improvement in the material's surface properties. Moreover, it was demonstrated that the optimal effect can be obtained after just 10 s of the plasma process. [ABSTRACT FROM AUTHOR]

Nowadays, the dependence on synthetic plastic-based materials for the preservation and transport of different types of products is very high, leading to major environmental and human health concerns, which highlights the importance of investigating sustainable options. Paper is a widely used bio-based material for packaging however, the development of newer and straightforward approaches to produce paper-based materials with increased functionalities and performance is still highly desired. In this work, we report the use of a bio-based photopolymerizable coating formulation, composed of tung oil, and using Darocur 1173 as photoinitiator, to develop functional papers with hydrophobic and improved water barrier properties, without compromising other properties. Coated paper samples were prepared, using different irradiation times (0, 15, 30, 60, and 300 s), to study the effect of this parameter on the properties of the coated papers. The ensuing coated papers presented pick-up values between 6 and 7 g/m2. Their hydrophobicity was significantly improved as evidenced by the increase in the contact angle values from about 71° to 127° and the significant decrease in the water absorption, measured by the Cobb test, from 108 down to 17 g/m2, upon a curing time of only 15 s. Furthermore, with this time of curing, the optical (viz. whiteness, brightness, and opacity) and mechanical properties (viz. tensile and burst strength) of paper were not affected. These results highlight the great potential of tung oil photopolymerizable coating formulations as a simple and promising alternative for the fabrication of more sustainable and functional paper packaging materials. [Display omitted] • Photopolymerizable bio-based coating for paper-based packaging materials • The obtained coatings confer high hydrophobicity to paper. • Papers with improved air barrier and mechanical properties were obtained. • Optimized curing time (15 s) compatible with manufacturing constraints [ABSTRACT FROM AUTHOR]