impingement, [ 11 ] tape-peeling, [ 11b ] waterimpact tests, [ 12 ] supersonic treatments, [ 12a ] or slight friction (a few centimeters or dozens of centimeters of abrasion with sandpaper). [ 13 ] Moreover, a host of current procedures either require complex processing and specialized equipment or are diffi cult to realize industrial-scale applications. [ 8b , 14 ] Clearly, the creation of a simple, low-cost superhydrophobic surface with excellent mechanical durability and practical utility for large-scale applications is urgently required. Recently, Lu et al. have developed a method to bond the self-cleaning coatings to the substrates by using adhesives; the resulting surfaces maintained their hydrophobicity after various types of destructive tests, including fi nger-wipe, knife-scratch, and 40 abrasion cycles with sandpaper tests. [ 15 ] However, such a two-layer system is unfavorable for paint construction.In the present work, we developed a polymer-based superhydrophobic composite coating by combining a methyl silicone resin with a superhydrophobic silica sol. To fabricate the superhydrophobic silica sol, we selected γ-aminopropyltriethoxysilane (APTES) and 1H,1H,2H,2H-perfl uorooctyltriethoxysilane (PFOTS) as the agglomeration agent and hydrophobic agent, respectively, with which to modify silica nanoparticles; the average diameter of this silica nanoparticles was about approximately 3-5 nm, which are smaller than other superhydrophobic nanoparticles reported in the literature to date. [ 15,16 ] We subsequently added a commercial methyl silicone resin to the superhydrophobic sol to enhance its mechanical durability. The coating exhibits remarkable superhydrophobicity even after being subjected to a fi nger-wipe test, a knife-scratch test, or 50 abrasion cycles with sandpaper. The coating exhibits high rigidity (pencil hardness of 9H), good fl exibility (impact resistance of 1 m kg) and great adhesion (5B).The superhydrophobic surface is attributed to a combination of topographical microstructures and chemical compositions. [ 17 ] When a drop of water (5 µL) was placed on the composite coating substrate, a perfect spherical water droplet formed with a CA of 166° and a SA of 1° ( Figure 1 a). The CAs were 137° and 129° for diiodomethane and edible oil, respectively, showing the coating's good oleophobicity. And the apparent surface free energy is 1.14 mJ·m −2 according to the Owens-Wendt method. The surface topography of the composite coating was examined by scanning electron microscopy (SEM). Numerous aggregated silica nanoparticles and micropores were observed to be distributed on the coated substrate (Figure 1 b). These particles and micropores can trap a large fraction of air, which is essential for The practical applications of superhydrophobic self-cleaning surfaces have been hampered by poor mechanical durability. Here, a composite coating that possesses excellent superhydrophobicity and robust mechanical durability is fabricated, consisting of a methyl silicone resin and a superhydrophobic sil...
Multivariate statistical techniques, including cluster analysis (CA), discriminant analysis (DA), principal component analysis (PCA) and factor analysis (FA), were used to evaluate temporal and spatial variations in and to interpret large and complex water quality datasets collected from the Shuangji River Basin. The datasets, which contained 19 parameters, were generated during the 2 year (2018–2020) monitoring programme at 14 different sites (3192 observations) along the river. Hierarchical CA was used to divide the twelve months into three periods and the fourteen sampling sites into three groups. Discriminant analysis identified four parameters (CODMn, Cu, As, Se) loading more than 68% correct assignations in temporal analysis, while seven parameters (COD, TP, CODMn, F, LAS, Cu and Cd) to load 93% correct assignations in spatial analysis. The FA/PCA identified six factors that were responsible for explaining the data structure of 68% of the total variance of the dataset, allowing grouping of selected parameters based on common characteristics and assessing the incidence of overall change in each group. This study proposes the necessity and practicality of multivariate statistical techniques for evaluating and interpreting large and complex data sets, with a view to obtaining better information about water quality and the design of monitoring networks to effectively manage water resources.
a,x-Triethoxysilane terminated poly(dimethyl siloxane) (PDMS) oligomer, a,x-triethoxysilane terminated perfluoropolyether (PFPE) oligomer, and acrylic polyols were first synthesized via an addition reaction and free-radical polymerization. Then, crosslinked network coatings based on PFPE/PDMS/acrylic polyols for marine fouling-release applications were prepared by a condensation reaction. The structure of the crosslinked network coating was characterized by Fourier transform infrared spectroscopy. The chemical composition of the coating surface was characterized by X-ray photoelectron spectroscopy. The thermal properties, surface energy, mechanical properties, adhesion, and antiseawater immersion performance of the coatings were systematically studied. The antibiofouling properties of the crosslinked network coating were evaluated by laboratory biofouling assays with the bacteria Escherichia coli and the fouling diatom Navicula. The results from the preliminary study suggested that this crosslinked network coating had good adhesion and promising antifouling properties that were comparable to a silicone standard.
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