Improving hydrophobicity and mechanical strength of rice straw paper using chitosan nanoparticles and beeswax coatings

Abstract Hydrophobic paper bags are gaining popularity as a sustainable and environmentally friendly alternative to conventional packaging materials. This study focuses on the development of hydrophobic paper bags from rice straw, a major agricultural waste. The pulp was prepared by boiling the straw with sodium hydroxide, followed by grinding and molding into paper sheets. Chitosan nanoparticles (CNP) were synthesized via the ionic gelation method and applied as a coating on the rice straw paper. Beeswax was then used as a secondary coating. The resulting paper sheets were evaluated for thickness, mechanical properties, thermal stability, and hydrophobicity. The results showed that CNP and beeswax-coated papers were significantly thicker than their non-coated paper. Mechanical testing demonstrated improvements in tensile strength and elongation at break for the coated papers, with the highest values observed in CNP and beeswax-coated samples. Fourier Transform Infrared Spectroscopy confirmed the successful integration of chitosan and beeswax into the paper matrix. Scanning Electron Microscopy images revealed enhanced smoothness and binding capacity in the coated papers. Thermal analysis indicated that CNP and beeswax-coated papers exhibited superior thermal stability compared to non-coated papers. Hydrophobicity tests confirmed that the CNP and beeswax-coated papers had excellent water resistance and self-cleaning properties, while heat sensitivity tests showed that the wax coating remained stable up to 50 °C. However, neither the CNP-coated nor the CNP with beeswax-coated papers exhibited a zone of inhibition against Staphylococcus aureus and Pseudomonas aeruginosa . These findings suggest that paper coating with CNP and beeswax significantly improves its physical, mechanical properties and hydrophobic properties.