Fire-resistant and hydrophobic paper based on Si₃N₄@PDMS core-shell nanowires with 3D interlocking structure

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 Si₃N₄ nanowires and polydimethylsiloxane (PDMS) is reported. Specially, the Si₃N₄@PDMS core-shell nanowires with 3D interlocking structure are designed, in which the Si₃N₄ nanowires act as the inorganic fire-resistant frameworks and the PDMS shell with low surface energy provides the hydrophobic surface. The Si₃N₄@PDMS core-shell nanowires are intertwined and interlaced to form a highly flexible Si₃N₄@PDMS paper. The tensile strength of Si₃N₄@PDMS paper is 6.19 MPa, indicating the good mechanical property. The obtained Si₃N₄@PDMS paper has the characteristics of writability, fire-resistance and hydrophobicity. The high thermal stability of Si₃N₄ nanowires makes Si₃N₄@PDMS paper exhibit excellent fire resistance. No obvious change is observed for the commercial paper with Si₃N₄@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 Si₃N₄@PDMS paper after mechanical damages, chemical corrosions and thermal treatments. Si₃N₄@PDMS paper can be used in oil/water separation and oil collection. More importantly, Si₃N₄@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.