Frost-resistant high-performance wood via synergetic building of omni-surface hydrophobicity

In humid/cold regions, natural wood is vulnerable to mildew, cracking or tremendous strength loss due to their intrinsic hydrophilicity and porous architecture. Herein we report an effective strategy to create omni-surface hydrophobic wood with high flexural strength and excellent frost-resistance. This facile method involves the removal of lignin/hemicellulose, omni-surface hydrophobic treatment and fast hot-pressing densification. Water contact angles of 156 +/- 4 degrees and 124 +/- 4 degrees were revealed on the outer surface and torn inner surface, respectively. The omni-surface hydrophobicity was achieved by the synergetic effect of steric hindrance of stringed silica nanoparticles and low surface energy of fluorosilylated groups. An easy, fast hot-pressing process offers fourfold increase in flexural strength to 228 MPa. Without hydrophobic treatment, the accelerated freeze-thaw tests cause a cliff drop in flexural strength and cracking for densified wood. In contrast, the omni-surface hydrophobic densified wood shows an excellent frost-resistance and dimensional stability. Such easy, scalable and effective approach holds great potential for developing high-performance, frost-resistant engineering materials in humid/cold regions.