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Hydrophobic protective layer improves mechanical strength of hemp textiles and paper
A silicone-containing, water-based polyurethane coating significantly improves the water resistance and mechanical stability of hemp fabric and paper – and opens up new application possibilities for cellulose substrates.
Hemp fabric and cellulose paper are sustainable materials with high application potential – but their limited water resistance and mechanical resilience hinder their wider industrial use. A research team from China has now developed a functionalised coating that addresses these weaknesses: A water-based polyurethane acrylate coating with silicone components (WPUASi) increases both the hydrophobicity and the strength of the substrates.
The emulsion, which is based on an interpenetrating polymer network (IPN), was applied to hemp textiles and filter paper. The water contact angle (WCA) increased from 0° to 127.5° for hemp and to 113.2° for paper. The mechanical characteristics also improved significantly: the tensile strength of the hemp fabric increased by 19 % and the folding strength of the filter paper increased 23-fold.
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Resistant even after washing
Even after several washing cycles, the treated substrates retained most of their hydrophobic and mechanical properties. This indicates good adhesion and stability of the coating. In addition, the WPUASi formulation was applied to other fibre-based materials such as cotton, polyester-cotton blends, acrylic fibres and wood-based materials (e.g. hardboard and balsa wood). Here too, the water contact angles were between 100° and 120°.
In a further experiment, the researchers combined the coating with curcumin to produce a UV-resistant, antibacterial and water-repellent multifunctional material based on hemp. The results show the potential of the novel formulation for use in functionalised, bio-based material systems.
Source: Deng, Lihua et al (2025): Simultaneously improving water resistance and mechanical strength of hemp fabric and paper substrates enabled by silicone-containing waterborne polyurethane surface coating. In: Progress in Organic Coatings, Volume 200, Article 108976.
