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The UV polymerization of multifunctional monomers is one of the most efficient methods available to generate three-dimensional polymer networks. Among the advantages of this technology are the high curing speed, the reduced energy consumption and the absence of VOC emissions ( i.e. the technique is considered eco-friendly). Thus it finds wide application in the production of coatings, as it is suitable for many different substrates (including the thermosensitive ones) and it is possible to cure selectively the irradiated area. Moreover, by tailoring the composition of the formulations, one can adjust a large variety of bulk and surface properties, depending on the characteristics required by a given field of application. The presence of inorganic phases into polymeric matrices can improve mechanical, optical, electronic, thermal and barrier properties as well as scratch and corrosion resistance of the coatings. When a homogeneous dispersion on a nanometre scale of the inorganic particles into the polymer film is obtained, the performances are dramatically increased. At the same time the transparency of the coatings, which is a very important property, is maintained, because no phase separation occurs between the inorganic and the organic part of the material.
We used two different strategies to obtain nanocomposites coatings via photopolymerization: the top-down approach (introduction of pre-formed inorganic nanoparticles inside a photocurable matrix) and the bottom-up approach (synthesis of the nanoparticles in situ in the photocurable resin via a sol-gel process).
The preparation of the coatings will be presented, comparing the different methods with examples where the inorganic nanophases are natural or modified clays and metal oxides such as SiO2 or TiO2 , the matrices employed are acrylic and epoxides. In each case the obtained films were characterized in their morphology (XRD, TEM), their thermal, mechanical, chemical and surface properties (DSC, TGA, DMTA, chemical resistance, contact angle, AFM, scratch resistance, corrosion resistance).
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