木材耐久性超疏水表面构建研究进展

木材作为一种天然可再生材料,富含亲水性基团且孔隙结构发达,因而具有很强的吸湿/水能力,易发生变形、开裂、腐朽等问题。基于“荷叶效应”原理,仿生构建木材超疏水表面是有效隔离木材与水分接触,赋予木材防水、防污、自清洁等优良特性的木材功能性改良新途径。然而超疏水木材在实际应用中不可避免地要受到刮擦磨损、阳光辐射、化学腐蚀等外界因素的影响,容易造成表面微/纳米粗糙结构的破坏或低表面能物质的降解,从而导致超疏水性能的降低或丧失,限制了超疏水木材的实际应用,因此设法提高木材表面超疏水涂层的机械稳定性和耐久性是亟待解决的关键问题。笔者首先分析了木材超疏水表面耐久性差的主要原因,介绍了木材超疏水表面耐久性能的测试方法,重点综述了木材耐久性超疏水表面的构建策略及其最新研究进展,最后对超疏水木材研究中存在的一些问题及发展趋势进行了总结和展望。

Research progress of durable superhydrophobic wood surface

As a natural,renewable and sustainable material,wood has a strong moisture/water absorption capacity due to the presence of abundant hydrophilic groups(e.g.,hydroxyl and carboxyl groups)in the cell wall components and its highly porous structure,which may cause severe practical problems of wood utilization such as deformation,cracking,fungal decay and discoloration.Although various chemical modification methods(e.g.,acetylation,furfurylation,and heat treatment)have been used to reduce or delay water/moisture absorption into wood,they cannot prevent water absorption upon the direct exposure of wood to liquid water.Nature world offers many examples of superhydrophobic surfaces(e.g.,lotus leaves and water strider legs),exhibiting great water-repellent properties with water contact angles higher than 150°.Superhydrophobic surfaces can minimize wood-water interactions and thus avoid problems associated with water absorption.By mimicking the lotus effect,creation of nanostructured superhydrophobic coatings on wood surface is a novel wood modification technique to impart wood with attractive characteristics such as water-repellency,anti-fouling,and self-cleaning functions.However,superhydrophobic wood surfaces are highly susceptible to environmental hazards such as scratch and abrasion,sunlight irradiation,and chemical etching,resulting in damages of the hierarchical structures and loss of the low-surface-energy components,and eventually leading to the decline or complete loss of its super water-repellency,which limits the practical application of superhydrophobic wood.Therefore,the enhancement of the mechanical stability and durability of the fabricated superhydrophobic coatings on wood substrate is currently a crucial issue that remains to be solved.In this review,the main reasons for the poor durability of superhydrophobic wood surface are firstly analyzed,and the test methods for assessing the durability of the superhydrophobic surface are presented.The strategies for constructing durable superhydrophobic wood surfaces and their latest research progresses are generally summarized.Finally,the challenges and prospects of the research on superhydrophobic wood are pointed out.