Nanostructured Coatings Obtained Via Cationic UV-Curing
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1005-Q02-05
Nanostructured Coatings Obtained Via Cationic UV-Curing Marco Sangermano1, Roberta Bongiovanni1, Giulio Malucelli1, Aldo Priola1, Ezio Amerio1, Doris Pospiech2, and Brigitte Voit2 1 Politecnico di Torino, Torino, 10129, Italy 2 IPF, Dresden, Germany INTRODUCTION Polymeric nanocoatings have drawn considerable attention , in recent years, due to improvements in various properties including scratch resistance, abrasion resistance, heat stability as well as other mechanical properties [1-3].Different meal oxide nanoparticles have been employed s filler, in particular SiO2, TiO2 and ZnO were deeply investigated in literature [4].The use of inorganic particles in the nanoscale range is particularly attractive with the aim of improving the polymer properties by controlling the degree of interaction between the polymer and the nanofiller [5]. As inorganic fillers a range of different metal-oxide particles can be dispersed in the polymeric matrix [6-8]. Particularly attractive is the use of inorganic particles in the nanoscale range with the aim of improving the properties of the polymers by controlling the degree of interaction between the polymer and the nanofillers [9] via a top-down approach.One major problem with nanosized particles is their homogeneous dispersion within the organic matrix avoiding macroscopic phase separation. An in-situ approach of preparing nanoparticles using sol-gel precursors is appealing for this reason; it involves a series of hydrolysis and condensation reactions starting from a hydrolyzable multifunctional metal-alcoxide as precursor for the inorganic domain formation [10] (bottom-up approach).The use of suitable coupling agent permits to obtain a strictly interconnected network preventing macroscopic phase separation. The coupling agent provides bonding between the organic and the inorganic phases, therefore well-dispersed nanostructured phases may result [11] and hybrid organic-inorganic materials are achieved. UV induced polymerization was employed for the polymer network build-up. UV Curing technique is getting an increasing importance in the field of coatings due to its peculiar characteristics. It is a process where UV light induces the polymer formation allowing to obtain a fast transformation of the liquid monomer into the solid film with tailored physico-chemical and mechanical properties. It is an environmental friendly technique because it is a solvent-free process. The substrate does not need to be heated as in the traditional thermal curing, therefore it guarantees the saving of energy and it allows to coat thermal-sensitive substrates. In the UV process radical or cationic species are generated by the interaction of UV light with a suitable photoinitiator, which induces the curing reaction of reactive monomers and oligomers [12].In the case of cationic polymerization, onium salts are used to generate very strong Bronsted acid upon photodecomposition [13], in particular lack of inhibition by oxygen, low shrinkage, good mechanical properties of UV cured materials and g
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