| Recently, the preparation and application of nano-and micro-sized capsules are becoming the hotspot in materials research. In the coatings field, micro/nanocapsules have been successfully used in the preparation of self-healing coatings, anticorrosive coatings, superhydrophobic coatings, and etc. These smart coatings can retain their functionality for a long time owing to the slow-release properties of the micro/nanocapsules. On the other hand, silicone oil has the advantages of low surface tension, high insulating ability, low evaporation, excellent weatherability and non-toxicity, and the ability to resist water, ice, pollution, fouling and conglutination, and is promising for preparation of functional coatings. Encapsulation of silicone oil within nano-or microcapsules would decrease the releasing rate of silicone oil and thus prolong the performance of the functional coatings, and even provide the silicone oil with new functionalities.In this study, silicone oil microcapsules with thin silica shell were readily prepared by miniemulsion technique, and were directly embedded in latex paints to prepare waterborne anti-icing coatings. All the research contents and results are shown as follows:(1) Silicone oil microcapsules with thin silica shell (about 20 nm in thickness) were readily prepared by miniemulsion technique. The emulsion droplets consisting of tetraethoxysilane (TEOS), dimethylsilicone fluid and octadecyltrimethoxy (OTMS) were first stabilized in water with sodium laurylsulfonate/triton X-100 (SLS/OP-10) as surfactants and subsequently aged under stirring at pH value of 7.5, during which the silica shell formed through hydrolysis and condensation of TEOS/OTMS at the oil droplet/water interface. The obtained microcapsule latex had a solid content of as high as 17.6 wt%. Adjusting the pH value of the miniemulsion to 7.5 during aging stage is paramount to get the microcapsules with well-defined core/shell structure as well as to improve the long-term storage stability of the microcapsule latex, which are absolutely benefit for practical application. The microcapsule size, around at 200 nm, was slightly changed with the mass ratios of SLS/OP-10 and TEOS/OTMS. The silicone oil microcapsules were directly embedded into waterborne coatings and showed a good slow-releasing property in tap water eroding experiments.(2) The as-obtained silicone oil microcapsules were embedded to latex paints to prepare waterborne anti-icing coatings. Effects of the type and amount of fillers (or pigments), the amount of silicone oil microcapsules, the pigment/resin (PB) ratio and the additives on the appearance, surface morphology and water contact angle (WCA) of the coatings were investigated. It was found that the hydrophobicity of the coatings was enhanced by addition of silicone oil microcapsule but not obviously increased with increasing content of silicone oil microcapsule. Nevertheless, higher hydrophobicity was achieved for the coating with high PB ratio. The highest WCA of about 130°was obtained by optimization of coating formulation. Unfortunately, superhydrophobic coatings can not be gotten via blending of latex paints with silicone oil microcapsules.(3) The long-term hydrophobicity and ice adhesion strength of the coatings were examined with a QUV accelerated weathering tester and a pull-off adhesion tester, respectively. The effects of silicone oil content and PB ratio on the long-term hydrophobicity and ice adhesion strength of the coatings were investigated. A higher silicone oil content and a PB ratio close to the critical pigment volume concentration favor long-term hydrophobicity of the coatings. An obvious decrease in ice adhesion strength was achieved for coatings with a PB ratio of 5.0 and a silicone oil content of 4.2%. For coatings with the same surface roughness, a higher water contact angle (WCA) leads to lower ice adhesion strength. However, for coatings with different surface roughnesses, the ice adhesion strength is dependent on surface roughness rather than on WCA. |
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