Amphiphobic Nanostructured Coatings for Industrial Applications

Durability of Lubricated Icephobic Coatings under Various Environmental Stresses

Icephobic coatings interest various industries facing icing problems. However, their durability represents a current limitation in real applications. Therefore, understanding the degradation of coatings under various environmental stresses is necessary for further coating development. Here, lubricated icephobic coatings were fabricated using a flame spray method with hybrid feedstock injection. Low-density polyethylene represented the main coating component. Two additives, namely fully hydrogenated cottonseed oil and paraffinic wax, were added to the coating structure to enhance coating icephobicity. Coating properties were characterised, including topography, surface roughness, thermal properties, wettability, and icephobicity. Moreover, their performance was investigated under various environmental stresses, such as repeated icing/deicing cycles, immersion in corrosive media, and exposure to ultraviolet (UV) irradiation. According to the results, all coatings exhibited medium-low ice adhesion, with slightly more stable icephobic behaviour for cottonseed oil-based coatings over the icing/deicing cycles. Surface roughness slightly increased, and wetting performances decreased after the cyclic tests, but chemical changes were not revealed. Moreover, coatings demonstrated good chemical resistance in selected corrosive media, with better performance for paraffin-based coatings. However, a slight decrease in hydrophobicity was detected due to surface structural changes. Finally, paraffin-based coatings showed better resistance under UV irradiation based on carbonyl index and colour change measurements.

Static Wettability of Differently Mechanically Treated and Amphiphobic-Coated Aluminium Surfaces

Wettability, roughness and surface treatment methods are essential for the majority of practical applications, where liquid-solid surface interactions take place. The present study experimentally investigated the influence of different mechanical surface treatment methods on the static wettability of uncoated and amphiphobic-coated aluminium alloy (AlMg₃) samples, specially focusing on the interaction between surface finishing and coating. Five different surfaces were prepared: as-received substrate, polished, sandpapered, fleece-abraded and sandblasted. After characterisation, the samples were spray-coated using an amphiphobic coating. The characterisation of the uncoated and coated samples involved measurements of the roughness parameters and the apparent contact angles of demineralized water and rapeseed oil. The coating was initially characterised regarding its adhesion to the sample and elevated temperature stability. The applied surface treatments resulted in the scattered sample roughness in the range of Sa = 0.3-15.8 µm, water contact angles of θ a p , w = 78°-106° and extremely low oil contact angles. Coating the samples more than doubled the surface roughness to Sa = 13.3-29 µm, whereas the initial surface treatment properties (structure, anisotropy, etc.) were entirely repressed by the coating properties. Coating led the water contact angles to increase to θ a p , w _ c o a t e d = 162°-173° and even more pronounced oil contact angles to increase to θ a p , o _ c o a t e d = 139°-150°, classifying the surfaces as superhydrophobic and oleophobic.

A Novel Simple Anti-Ice Aluminum Coating: Synthesis and In-Lab Comparison with a Superhydrophobic Hierarchical Surface

A simple process to obtain a slippery surface with anti-ice and ice-phobic properties has been developed and characterized in laboratory. The coating is realized by growing a nanostructured pseudo-boehmite on an aluminum substrate and applying an environmentally compatible final functionalization consisting of a fluorine-free oligomeric short-chain alkylfunctional silane. The resulting surface is conceptually similar to a slippery liquid infused porous surface (SLIP) material, but the porous infrastructure is inorganic and the process to generate it is very simple, rapid and economic. The coating performance in terms of hydrophobicity at room and low temperatures, ice nucleation temperature and ice adhesion forces were assessed in laboratory. Moreover, hydrophobicity persistence was tested after prolonged immersion in acid, basic and saline solutions while the durability of ice-phobic behavior was assessed by repeated shear stress tests. Results are compared with those of a superhydrophobic hierarchical aluminum surface obtained with a fluorinated siloxane. The novel coating shows very good anti-ice properties and relevant durability, with some differences from the fluorinated surface. The novel slippery coating process is promising for industrial applications, also taking into account its environmental compatibility, simplicity and low cost.

Effect of Chitosan- and Alginate-Based Coatings Enriched with Cinnamon Essential Oil Microcapsules to Improve the Postharvest Quality of Mangoes

During this study, fresh mangoes were packed into multilayer coatings made from chitosan containing cinnamon essential oil microcapsules and alginate solutions that were alternately deposited on the mango surfaces by electrostatic interaction. We then compared the physical and chemical indexes to examine the changes in the mangoes during 14 d of storage. The results showed that the microcapsules prepared in the experiment were of uniform size, with the sustained release of essential oil exceeding 168 h. Compared with uncoated mangoes, the mangoes coated with the coatings could effectively inhibit the decrease of the titratable acid, soluble solids, and vitamin C contents; slow down the increase of the weight loss and pH; delay the appearance of mango respiration peaks; and preserve the firmness at storage conditions of 25 °C and 50% RH. Our findings revealed that mangoes without treatment showed losses in their edible and commercial value after 14 days in storage, and the mangoes coated with five layers still retained food and commercial value. Cross-sectional scanning electron microscopy images of the coatings showed that they had distinct layers and were of good uniformity and tight binding, and they also had good adhesion to the mango surface. These findings provide important insights into the use of coatings for the packaging of fruits during storage, which is essential for promoting the application of coatings for packaging preservation without big cost and expensive equipment.