UV-cured coatings based on waterborne resins and SiO 2 nanoparticles Anna Di Gianni, Roberta Bongiovanni, Stefano Turri, Flavio Deflorian, Giulio Malucelli, Giancarlo Rizza Ó FSCT and OCCA 2008 Abstract The UV curing technique in combination with the use of waterborne resins is very attractive since it gives the opportunity to get solid coatings by means of ecofriendly processes. We found that it is possible to use such UV curable water-based formu- lations as matrices for the preparation of nanocom- posites in which the filler is generated in situ by means of the sol–gel chemistry. We prepared silica-based nanocomposites and characterized them comparing their performances with those of the silica-free coat- ings. Moreover, the article discusses the influence of the addition of a coupling agent between the organic and inorganic phase on the final properties of the nanocomposite. Keywords Coatings, Nanocomposites, Photopolymerization, Sol–gel, Waterborne, Corrosion Introduction Water soluble polymers have a great interest for both academia and industry since they can offer many advantages in different applications, including coatings applications. In fact, water-based resins are, first of all, ecofriendly and are proposed as an alternative to traditional paints. 1–4 At present, however, waterborne products are considered unsatisfactory as the applica- tion conditions are often critical; they are difficult to apply because of their rheological behavior and poor wetting, temperature and humidity have to be strictly controlled for correct curing conditions, etc. Moreover, once applied, their performances are usually inferior to the traditional products. The use of water-based resins in combination with the UV-curing technique is also very attractive since the UV-curing process offers many advantages too, as reported by Decker. 5,6 In fact, it assures high curing rates and a low energy consumption, it allows for curing selectively the irradiated area, and it is suitable for all kinds of substrates and for any coatings application. In most cases, the UV reactive formulation does not contain any solvent, which is an additional interesting feature of the process. When waterborne resins are introduced, an additional drying step is required before curing by UV irradiation. However, water as a diluent is an effective way to reduce the formulation viscosity, avoiding the addition of low molecular weight species, which, being volatile, can be unsafe for the environment. The properties of the UV-cured waterborne coat- ings may need some improvements depending on the field of applications. One possibility to get higher performance materials is including inorganic nanopar- ticles in the polymer network. 7 In fact, nanocompo- sites, which have been receiving great attention in the last decades, usually offer better properties in com- parison with the neat polymer matrix. For example, A. Di Gianni (&), R. Bongiovanni, G. Malucelli Dipartimento di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy e-mail: anna.digianni@polito.it S. Turri Dipartimento di Chimica, Materiali e Ingegneria Chimica ‘‘G. Natta’’, Politecnico di Milano, P.zza L. da Vinci 32, 20133 Milano, Italy F. Deflorian Dipartimento di Ingegneria dei Materiali, Universita ` di Trento, V. Mesiano 77, 38050 Trento, Italy G. Rizza Laboratoires des Solides Irradies, Ecole Polytechnique/ CEA (DSM-DRECAM)/CNRS (UMR 7642), 91128 Palaiseau Cedex, France J. Coat. Technol. Res., 6 (2) 177–185, 2009 DOI 10.1007/s11998-008-9137-1 177