Lignin-based superhydrophobic coating with good abrasion resistance enhanced by compositing aminoized polystyrene microspheres

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Superhydrophobic coating has the characteristics of waterproof, anti-pollution and self-cleaning, showing a very wide application prospect in many fields. It could be obtained by the combination of suitable roughness and low surface free energy. Renewable and low-cost lignin has certain inherent advantages in constructing super-hydrophobic coatings as rough structure, but the poor abrasion resistance limits its further development. To improve the abrasion resistance, acetonitrile extracted lignin (AEL) was employed as the main material, aminozed polystyrene (PS) microspheres with good mechanical strength and dispersibility as the reinforcer to construct AEL/PS composite particles through solvent exchange and self-assembly. Subsequently, the AEL/PS composite particles were fixed to wood by both hexadecyltrimethoxysilane (HDTMS) and methyltrimethoxysilane (MTMS) as the composite modifiers, combining with polydimethylsiloxane (PDMS) as the binder to prepare superhydrophobic coating with water contact angle of 160.8° and sliding angle of 5°. The resulting coating always exhibits superhydrophobicity even after the abrasion distance of 660 cm (33 cyclic abrasion), with the improvement of 73 % compared with before the introduced PS microspheres, exhibiting excellent abrasion resistance. Also, it exhibits excellent adhesion, and it could maintain superhydrophobicity after 1000 cyclic tape-stripping tests. In addition, the system shows outstanding stability, and it can be irradiated under high intensity ultraviolet (UV) irradiation (800 W, wavelength of 365 nm) for 8 h without losing superhydrophobicity and it maintained superhydrophobicity after immerging in various solutions (PH=4, PH=14, 3.5 wt% NaCl, ethyl alcohol, tetrahydrofuran) for 2 h. Moreover, the preparation process is simple and fluorine-free, providing a foreseeable prosperity for biomass based superhydrophobic coating with excellent abrasion resistance. Fig. 1. Formation and working mechanism of AEL/PS composite superhydrophobic coating • The use of lignin nanospheres increases value-added applications of lignin. • Using lignin to wrap polystyrene microspheres enhances the abrasion resistance. • The superhydrophobic coating is prepared without fluorine. • Improved mechanical properties by 73 % compared with before wrapping.

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