Sustainable hydrophobic coating of paper utilizing silica nanoparticles

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The preparation of hydrophobic paper involved applying thin layers of non-biodegradable plastics to the paper, which made recycling difficult and contributed to microplastic pollution. In this study, we present a new method for coating paper to enhance its hydrophobic properties and long-term effectiveness of the hydrophobic surface. We use sustainable materials such as polyvinyl alcohol (PVOH), chitosan, monoaminopropyl terminated polydimethylsiloxane (PDMS), and silica nanoparticles (SiNPs). We use hexamethylene diisocyanate isocyanurate trimer (HDIT) and (3-aminopropyl)triethoxysilane (APTES) to link the chemicals covalently and to modify surface of SiNPs with amino groups, respectively. We also integrate PVOH to reduce the cost of the coating solution without compromising its hydrophobicity. We confirmed the long-lasting hydrophobicity of the coated paper by measuring the water contact angle for 60 min. When the paper coated with a solution containing amino SiNPs dispersed in ethanol, the maximum contact angle at 10 s and at 1 h were 132.3° and 95.7°, respectively. Additionally, the hydrophobic coating solution can be removed for potential recycling by treating it with hydrochloric acid or acetic acid. Our developed coating solution provides an environmentally friendly option for various paper-based applications, promoting paper recycling and contributing to sustainable development and environmental protection efforts.