Towards the development of superhydrophobic carbon nanomaterial coatings on wood

Carbon nanomaterials (CNMs) have recently been used to form superhydrophobic coatings on metals, synthetic polymers or textiles. Here we investigate the possibility of using carbon black (CB), graphene (Gr) and carbon nanotubes (CNTs), as water repellent agents on naturally hydrophilic wood. We show that it is possible to form homogeneous CNM coatings on any type of wood via simple methods of drop casting and dip coating, using CNMs dispersed in organic solvents or water. Contact angle measurements of wood coated with only 0.05 g/m(2) CNTs and 0.25 g/m(2) Gr gave the results exceeding 130 degrees, indicating apparent hydrophobicity. Yet, high adhesion of the droplets was observed, simultaneously suggesting a "rose petal" type of superhydrophobic behavior. That may be explained by the formation of micro-nano architectures in which low surface energy CNMs deposited on microrough surface of wood cause superhydrophobicity. Yet, due to heterogeneity of wood, some part of hydrophilic surface is still uncovered, resulting in high adhesion of water. Finally, although Gr and CNT were only physically bond to wood surface, the hydrophobic properties of CNM coatings were maintained after sandpaper abrasion test. Moreover, wood fibers and particles covered with Gr showed the decrease of water absorption equal 98% and 87%, respectively.