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Cellulosic material is considered to be excellent for food packaging due to its low cost, easy degradability, and high recyclability rates. However, its application is still limited due to its porous structure and high hydrophilicity, which provide high permeabilities to grease, gas and water vapor. One solution to fix these issues and to bring new functionalities that can also extend food shelf life is to coat the paper substrate with biopolymers containing nanoparticles and/or components with antioxidant and/or antimicrobial activities. In this regard, the aim of this study was to review some aspects of the current knowledge critically and didactically on applications of biopolymer-based coatings incorporated with active components and/or nanoparticles on paper/paperboard materials usually applied as primary cellulosic active packaging. Studies have shown that this combination can positively improve the physical, mechanical, and barrier properties of cellulosic packaging, along with the enhancement of antioxidant and antimicrobial activities. A better understanding of these aspects enables the use of other active compounds to develop more functionality to the packaging itself as well as to apply it to food packaging in general. [ABSTRACT FROM AUTHOR]

The ability to pattern highly conductive features on paper substrates is critically important for applications in radio frequency identification (RFID) tags, displays, sensors, printed electronics, and diagnostics. Ink-jet printing particle-free reactive silver inks is an additive, material efficient and versatile strategy for fabrication of highly conductive patterns; however, the intrinsic wetting properties of cellulose based papers are not suitable to serve as substrates for this process. This study reports one-step and practical modification of the surface of paper substrates using industrially available materials. The paper substrates were dip-coated with films of hydrocarbon and fluorocarbon based polymeric resins. Ink-jet printing particle-free reactive silver inks on the modified paper substrates followed by fast thermal annealing resulted in highly conductive patterns. The coatings improved the conductivity of the patterns and reduced the number of printing layers required to obtain conductivity. We finally demonstrated fabrication of a printed RFID tag on the coated paper substrates operating at the frequency range of 865–870 MHz. [ABSTRACT FROM AUTHOR]

Abstract: Paper has been proposed as an alternative substrate material for graphene-based strain gauges due to its high flexibility and accessibility when compared to the conventional substrates such as polymer that is not only rigid but also not recyclable. In the fabrication of graphene-based strain gauges on paper, inkjet printing is commonly used as the main deposition method of graphene on paper as this process allows a systematic control of strain gauge resistance by manipulating several factors such as print passes and drop spacing. However, the availability of inkjet printers that allows the printing of graphene solution is an issue as industrial inkjet printers can be obtained only at a premium price while modification of commercial inkjet printers is a must to replace the original ink with graphene ink. To counter this issue, a commercial photo paper has been used for the first time as a substrate during vacuum filtration of graphene solution for layer-layer assembly of strain gauges on paper. With the resulting gauge factor of up to 83 at the maximum and minimum strain of 1.4% and 0.03% (sensitivity of 1.25%) respectively, the fabricated strain gauge from photo paper shows the potential of paper to be used as a component in the future wearable device. Meanwhile, the advantages of using vacuum filtration as the selected technique for the deposition of graphene meanwhile are demonstrated in this work by varying the gauge factor through controlling the graphene deposition volume.Graphical abstract: [ABSTRACT FROM AUTHOR]

In this study, a cost-effective way to deposit the silver nanoparticles (AgNPs) on paper egg trays was developed, which proved suitable for prolonged storage of table eggs for house-hold use without deterioration of egg quality. Silver nanoparticles were synthesized based on chemical reduction approach and mixed with gelatin-chitosan mixer used as a colloidal stabilizer as well as fixing agent. AgNPs-doped paper egg trays were characterized by TEM, SEM, FTIR, EDX and XRD. AgNPs containing egg trays were tested for its bactericidal effect against commonly found bacteria on egg shells, E. coli, S. aureus, Streptococcus spp and Salmonella spp. Storing of eggs in the AgNPs-deposited paper egg trays improved the shelf-life of the eggs by more than 14 days compared to controls (eggs stored in conventional trays). In conclusion, the developed paper trays possessed strong antimicrobial activity and it could be an effective storage material for eggs. [ABSTRACT FROM AUTHOR]

Vegetable oils were combined with recent nanotechnology as a sustainable method for tuning the hydrophobicity of cellulose and paper surfaces. Different soy-, sunflower-, corn-, castor-, rapeseed- and hydrogenated oils were incorporated into an aqueous dispersion of hybrid styrene maleimide nanoparticles. Here, we investigate the formation of novel coatings from these dispersions and their performance on paper and paperboard, compared with model aluminum substrates. The coated papers are evaluated by static and dynamic contact angles, microscopy, atomic force microscopy, infrared and Raman spectroscopy. The nanoparticle pigments form a porous coating after drying, while the water repellence and hydrophobicity of paperboard and paper improved with contact angles of 90-99° after drying and 98-112° after ageing. The coatings with poly(unsaturated) oils have best hydrophobicity for dispersions with an optimum viscosity of 115-150 cp required for good coverage of the paper. While homogeneous coverage of the cellulose fibers is a primary requirement, thin coatings often provide higher contact angles on paper due to roughness of the underlaying fibrous surface. After ageing, the coatings are chemically stable without oil leakage and constant imide content, while an increase in contact angles is attributed to variations in coating morphology through local re-arrangements over the paper substrate. [ABSTRACT FROM AUTHOR]

Nanoparticles of partially imidized poly(styrene-maleic anhydride) were applied from an aqueous dispersion as a one- or two-layer coating onto paper substrates, for controlling the paper surface hydrophobicity and improving the water barrier resistance. The effect of deposition conditions and thermal treatments on the topography and properties of the coating was studied by scanning electron microscopy, atomic force microscopy (AFM), contact angle measurements, and friction measurements. The wettability of paper surfaces with adsorbed nanoparticles can be controlled by tuning the chemical and topographical surface parameters: the water contact angles were found to increase at higher imide content as determined by Raman spectroscopy (depending on synthesis and thermal treatment), and higher average surface roughness determined by AFM (depending on the deposition method). The present technique may serve as a unique replacement for chemical treatments hydrophobizing fibrous substrates. [ABSTRACT FROM AUTHOR]