Hybrid network or 3 sir rsio 15 n rsio 15 m rsio15 m

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hybrid network (OR) 3 SiR’ R’(SiO 1.5 ) n R’(SiO 1.5 ) m R’(SiO 1.5 ) m Coating Drying Scheme 6.1 General schemes for the preparation of sol–gel ORMOSIL ( top ) and ORMOCER ( bottom ) nanocoatings.
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Silica-Based Sol–Gel Coatings 151 6.2 A Green, Simple Technology The hydrolysis of silanes aff ords the release of plentiful alcohol (in normal silanes, more than 50% of their weight), which can be readily distilled yielding waterborne VOC-free sol–gel coating formulations that today are widely (and increasingly) used to combat corrosion, friction, stick and fouling, due to a number of unique advantages like room temperature synthesis, chemical inertness, high oxidation and abrasion resistance, excellent thermal stability, and little or none health hazard [10]. In the early 2000s, sol–gel coatings made of silanes formulated in water or in non-toxic alcohols were firstly used (at Boeing) to protect aircraft fuselage, thereby replacing at least a fraction of the highly toxic Cr(VI) present in the chromates conventionally used, and drastically reducing the amount of volatile organic compounds (VOCs) present in traditional formulations [11]. Since then, numerous companies, both large and small (including, for example, Nanogate and Evonik ), have started to commercialize silane- based anti-stick, scratch-proof, anti-mist and anti-corrosion coatings based on sol–gel inorganic–organic nanochemistry technology. The sol–gel coating fabrication procedure is general (Scheme 6.2). Th e hydrolysis of silanes is followed by alcohol removal and then by addition of fillers and one or more functional species (pigment, anti-microbial, fragrance, UV absorber, photocatalyst, etc.) according to the required application. This functionalization step uniquely allows creating coatings for unprecedented large range of applications. The coating formulation is generally a transparent, low-viscosity, solvent-free sta- ble liquid, with a shelf life of several months. The liquid coating can be applied on single side or both sides of a substrate via spray, dip or other coating application method, after which the coating is cured either by simple drying under atmospheric conditions, by mild heat treatment, or by UV light or ammonia curing, depending on the coating. The functional sol–gel coating thus provides a material’s interface with new, enhanced physical, chemical, mechanical, optical, electrical or biological properties (Scheme 6.3). Formulation and sol-gel preparation Coating deposition on substrate (metal, polymer, wood, glass etc.) Curing of the coating Scheme 6.2 The sol–gel coating fabrication procedure (adapted from Ref. [1], with kind permission).
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152 Biobased and Environmental Benign Coatings Schmidt [ 12 ] Minami [8], Böttcher [ 13 ], Ferreira [ 14 ], Bright and Detty [ 15 ], Akid [ 16 ], Barbé [ 17 ] and their coworkers are among the scientists who largely con- tributed to major advances in the field.
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  • Sol-gel, Formulations, Sol–Gel Coatings

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