Superhydrophobic durable coating based on UV-photoreactive silica nanoparticles

Abstract

Superhydrophobic surfaces can be obtained by tailoring both the chemistry and roughness topography, mimicking the Lotus leaf characteristics. Most of the synthetic superhydrophobic surfaces reported have been composed of micro and nanoparticles (NPs) embedded in polymer-based coatings. The particles which tailor the topography are bonded to the base polymers by weak secondary forces. Consequently, the topography integrity is highly affected by handling and surface drag making them unsuitable for long term applications. This work is focused on promoting covalent bonding between the NPs and the base polymer to obtain durable superhydrophobic surfaces. The rough topography was achieved by ultraviolet (UV) curing of SiO 2 NPs containing a photoreactive benzophenone moiety in addition to methylated fumed silica NPs which can bind covalently to the polymer base coating, on UV radiation. The hydrophobic chemistry was obtained by fluoroalkylsilane top coating. Coating durability was evaluated using surface air drag and accelerated weathering conditions (UV radiation, humidity and temperature). Results indicated that the proposed approach resulted in superhydrophobic surfaces having high contact angle (>150 ) and low sliding angle (<10 ) with improved long term durability.

The Role of Roughness in Random Superhydrophobic Surfaces

“…The level of interest in superhydrophobic surfaces, which are characterized by a contact angle (CA) above 150° and a sliding angle (SA) below 10°, has increased in the last decade due to their potential for use in applications such as self-cleaning, anti-corrosion, anti-fog, drag reduction, low water permeation, super-omniphobic surfaces and ice-repellency . However, most of the state of the art superhydrophobic coatings lack durability, thus the development of a durable coating has been the subject of recent efforts [23][24][25][26][27][28].…”

Thermomechanical Mechanisms of Reducing Ice Adhesion on Superhydrophobic Surfaces

“…The first is related to the hydrophobic chemistry of the top coating layer, and the second factor has to do with the possibility to obtain covalent bonding of the silica NPs, which govern the roughness, to the polymer coating using radical chemistry. 49,50 The proposed hypothesis can be seen in Figure 1. Accordingly, the coating contains an ultraviolet (UV) curable photoinitiator that upon radiation initiates a radical type reaction with subsequent covalent bonding of the silica NPs to the polymer resin.…”

Overview of Silica-Polymer Nanostructures for Waterborne High-Performance Coatings

“…Desirable properties in waterborne coatings include flexibility [ 29 , 88 , 117 ], adhesion [ 81 , 118 , 119 ], wear resistance [ 92 , 102 , 120 , 121 , 122 ], and durability [ 120 ]. Among the possibilities for added coating functionality are, for example, flame retardancy [ 119 ], solvent and chemical resistance [ 123 , 124 ], stain resistance [ 102 , 124 ], anti-cavitation [ 81 ], extreme robustness (for space-based applications) [ 125 ], antimicrobial activity [ 126 , 127 , 128 , 129 , 130 , 131 ], superhydrophobicity [ 84 , 95 , 124 , 132 , 133 , 134 , 135 , 136 , 137 , 138 ], or photoactive fluorescent coatings [ 29 ] presented in Table 3 .…”

“…This is an extremely interesting property, with application in self-cleaning, anticorrosion, antipollution, self-healing, and ice repellent surfaces [ 142 ]. Coatings with contact angles above 150° have been prepared using nanoparticles modified with different hydrophobic groups (e.g., fluorinated) [ 124 , 133 , 134 , 135 , 136 , 138 ] and modulating the roughness of the surface (e.g., using raspberry-like structures) [ 95 , 115 , 132 ]. Nahum et al prepared nanocomposite coatings based on urethane acrylate and epoxy, containing SNPs functionalized with photoreactive benzophenone groups and a fluorinated silane [ 134 ].…”