Design and performance evaluation of sunflower straw biochar–based photothermal hydrophobic wood

Abstract

Wood—a natural biomass resource—contains abundant hydroxyl groups that easily absorb moisture, making it hydrophilic. However, excessive amounts of moisture can deform and decay wood, leading to its poor dimensional stability and limiting its applicability. In particular, the surface of wood is prone to freezing when exposed to cold environments. Epoxy resin (EP) is frequently employed to prevent this issue and improve the service life of wood. Herein, the surface of wood was treated with EP and 3-(methacryloyloxy)propyltrimethoxysilane (KH570)-modified sunflower straw biochar (KH570@SFBC; the treated wood is referred to as KH570@SFBC-wood) to fabricate a coating with excellent photothermal properties, hydrophobicity, and durability. The changes in the static water contact angle and photothermal properties of wood under different lighting conditions were investigated. Results revealed that under these conditions, the surface temperature of KH570@SFBC-wood was higher than that of natural wood. Under 1-sun illumination (1000 W/m²), the surface temperature of KH570@SFBC-wood was 141.7 ℃ and ice melted on the surface within 10 s. KH570@SFBC-wood exhibited excellent hydrophobicity under harsh environmental conditions, such as while undergoing ultrasonic treatment and sandpaper abrasion as well as when immersed in a corrosive solvent. It also exhibited excellent stain resistance to liquids such as tea, juice, cola, milk, and coffee, which are commonly used in daily life. The developed coating exhibited excellent hydrophobicity, chemical stability, mechanical stability, photothermal stability, and self-cleaning and antifouling properties. Overall, the aforementioned fabrication method effectively improved the photothermal properties of wood and prolonged its surface freezing time, thereby expanding its applicability.