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Enhancing paper hydrophobicity is of key importance for many paper-based applications. Fatty acids or vegetable oils and their derivatives replace environmentally harmful conventional coating materials but still require challenging chemical reactions for covalent attachment onto paper. Here, we show that simple storage of olive oil-coated cotton linter paper at 70 °C and subsequent Soxhlet extraction is able to endow paper with hydrophobic properties, reaching water contact angles above 130°. In-depth chemical and morphological analytics show the relevance of temperature and air accessibility during the aging process compared with aging at ambient temperature and under the exclusion of oxygen, underlining the importance of assessing a coating's long-term performance and stability under diverse storage conditions. Simple storage of vegetable oil-coated paper at elevated temperatures followed by extraction proves to be an easy way to produce stable covalently attached hydrophobic paper coatings with exceptionally low coating amounts. [ABSTRACT FROM AUTHOR]

Cellulosic-based materials such as hemp fabric and paper have combined characteristics of renewability, biodegradability, flexibility, and recyclability. However, regular products are not suitable for use in unconventional applications due to inherent limitations, and accordingly, enabling new capabilities is a necessity. To this end, the conversion of regular hemp fabric and paper into high-strength products with hydrophobic function via surface engineering was explored. The fluorinated waterborne polyurethane (FWPU) emulsions were first synthesized as functional coatings by in-situ polymerization. The structure and properties of the FWPU emulsion and film were characterized by FTIR, XRD, SEM, TG, and XPS. The results showed that the grafting of perfluorooctanol imparts WPU film excellent hydrophobicity, and the water contact angle increases from 71.2° to 105.9°. After the FWPU coating, the water contact angles of the hemp fabric and paper increase from 0° to 117.1° and 112.8°, respectively. Quite encouragingly, the coating generation of waterborne polyurethane-derived functional additives led to the increase of mechanical strength by more than 23% and 82%, in the case of qualitative filter paper and hemp fabric. Meanwhile, the folding strength of filter paper is increased by 132 times. Overall, this functionalized waterborne polyurethane coating would direct paper and hemp fabric toward diversified applications. [ABSTRACT FROM AUTHOR]

Paper with simultaneous fire-resistance and hydrophobicity have greatly potential applications in the fields of packing, storage and delivering information, which attracts increasing attention recently. Different from the traditional cellulose-based paper which is extremely easily damaged by water and fire, a new type of highly flexible, fire-resistant and hydrophobic paper based on Si 3 N 4 nanowires and polydimethylsiloxane (PDMS) is reported. Specially, the Si 3 N 4 @PDMS core-shell nanowires with 3D interlocking structure are designed, in which the Si 3 N 4 nanowires act as the inorganic fire-resistant frameworks and the PDMS shell with low surface energy provides the hydrophobic surface. The Si 3 N 4 @PDMS core-shell nanowires are intertwined and interlaced to form a highly flexible Si 3 N 4 @PDMS paper. The tensile strength of Si 3 N 4 @PDMS paper is 6.19 MPa, indicating the good mechanical property. The obtained Si 3 N 4 @PDMS paper has the characteristics of writability, fire-resistance and hydrophobicity. The high thermal stability of Si 3 N 4 nanowires makes Si 3 N 4 @PDMS paper exhibit excellent fire resistance. No obvious change is observed for the commercial paper with Si 3 N 4 @PDMS paper as the fire-shielding layer after heating for 30 min. In addition, the contact angles of water droplets are all greater than 110° over the surfaces of Si 3 N 4 @PDMS paper after mechanical damages, chemical corrosions and thermal treatments. Si 3 N 4 @PDMS paper can be used in oil/water separation and oil collection. More importantly, Si 3 N 4 @PDMS paper can be used for writing without being damaged by fire or water. The present work may inspire the development and application of functional paper and is expected to become a breakthrough in the traditional paper industry. [ABSTRACT FROM AUTHOR]

Hydrophobic coatings are of utmost importance for many applications of paper-based materials. However, to date, most coating methods demand vast amounts of chemicals and solvents. Frequently, fossil-based coating materials are being used and multiple derivatization reactions are often required to obtain desired performances. In this work, we present a solvent-free paper-coating process, where olive oil as the main biogenic component is being used to obtain a hydrophobic barrier on paper. UV-induced thiol-ene photocrosslinking of olive oil was pursued in a solvent-free state at a wavelength of 254 nm without addition of photoinitiator. Optimum reaction conditions were determined in advance using oleic acid as a model compound. Paper coatings based on olive oil crosslinked by thiol-ene reaction reach water contact angles of up to 120°. By means of Fourier transform infrared spectroscopy and differential scanning calorimetry, a successful reaction and the formation of a polymer network within the coating can be proven. These results show that click-chemistry strategies can be used to achieve hydrophobic polymeric paper coatings while keeping the amount of non-biobased chemicals and reaction steps at a minimum. [ABSTRACT FROM AUTHOR]

Hydrophobic coatings are of utmost importance for many applications of paper-based materials. However, to date, most coating methods demand vast amounts of chemicals and solvents. Frequently, fossil-based coating materials are being used and multiple derivatization reactions are often required to obtain desired performances. In this work, we present a solvent-free paper-coating process, where olive oil as the main biogenic component is being used to obtain a hydrophobic barrier on paper. UV-induced thiol-ene photocrosslinking of olive oil was pursued in a solvent-free state at a wavelength of 254 nm without addition of photoinitiator. Optimum reaction conditions were determined in advance using oleic acid as a model compound. Paper coatings based on olive oil crosslinked by thiol-ene reaction reach water contact angles of up to 120°. By means of Fourier transform infrared spectroscopy and differential scanning calorimetry, a successful reaction and the formation of a polymer network within the coating can be proven. These results show that click-chemistry strategies can be used to achieve hydrophobic polymeric paper coatings while keeping the amount of non-biobased chemicals and reaction steps at a minimum.

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]

Using biobased polyelectrolytes to emulsify natural fatty molecules is one possible key technology to create sustainable materials. The emulsions can be used in papermaking instead of synthetic hydrophobizing agents or in nonwoven manufacturing to create strong, hydrophobic textile-like materials. This article investigates a novel emulsification system based on a polyelectrolyte complex between chitosan dissolved in citric acid and carboxymethyl cellulose together with sunflower (Helianthus annuus) oil. Viscose nonwoven treated with the emulsion had a contact angle of over 120°. Tensile tests showed that the produced paper and nonwoven materials achieved high dry and, especially, high wet strength. Infrared spectroscopy illuminated the impact of heat curing the binder, and electron microscopy showed that the oil droplets from the emulsion were spread across the fibre surface. The results from this study enable sustainable nonwovens to be applied in areas where high dry and wet strength and water repellence are required; this includes outdoor applications, including agricultural mulch films, where nonwoven is used frequently and a sustainable approach is urgently needed to reduce the accumulation of plastics in the environment. [Display omitted] • Polyelectrolyte complex based on chitosan and carboxymethyl cellulose can emulsify sunflower oil. • The emulsion can be used as a biobased binder to replace fossil-based binders in nonwoven. • Cellulosic material treated with the binder receive high dry- and wet strength. • Contact angles of more than 120° can be reached with the emulsion-based polyelectrolyte complex binder. [ABSTRACT FROM AUTHOR]