UV-Cured nanostructured coatings

The UV-induced polymerization of multifunctional monomers has found a large number of applications in various industrial fields, mainly in the production of films, inks and coatings. In particular epoxy resins are widely used in industry, especially in the aerospace and electronic applications, due to their excellent thermal and dimensional stability, high modulus and excellent solvent resistance. However, especially epoxy polymers based on bisphenol-A structure are inherently brittle and toughening additives are needed for specific applications Advanced multifunctional coatings were prepared by UV curing of epoxy based formulations containing hyperbranched polymers (HBP) and an epoxy functionalized alkoxysilane additive. Advanced scratch resistant and tough nanocomposite epoxy coatings were obtained by properly selecting the formulation components.Regarding the surface properties modification of cured materials, the hydrophilicity of an epoxy coating was enhanced by a chemical modification that increases the surface energy and decreases the contact angle of a water drop: in this case we have achieved surface modification of epoxy cured network for the enhancing of surface hydrophilicity via click chemistry.The combination at the nanosize level of organic-inorganic domains in a single material could be very important for the achievements of multifunctional properties. These innovative advanced materials could find promising applications in fields including optics, electronics, membranes, sensors, catalysis and protective coatings. The first approach for the preparation of organic-inorganic nanostructured epoxy coatings concerns the incorporation of inorganic nanoscale materials, by dispersion of the inorganic nanoobject in the polymeric matrix or, following a second approach, via an in-situ generation through a sol-gel process. In both cases the key point is the achievement of a full deagglomeration of the nanoparticles within the epoxy matrix. Even though the particles might be well dispersed in the prepolymer solution, aggregation might occur in the matrix, especially during the thermal curing process. Inorganic nanoparticles such as, SiO2, TiO2, Fe2O3, and others, were dispersed as nanofiller into an epoxy UV-curable monomer in order to improve hardness and scratch resistance of the cured coatings. Epoxy based nanocomposites with advanced and outstanding properties were also obtained by carbon-nanotubes (CNT’s) or grapheme-oxide dispersion. An important increase of electrical surface conductivity was obtained in the cured materials. Alternatively, a dual curing UV-Thermal process involving a sol-gel technique was used in order to generate in-situ the inorganic domains. Both, the epoxy ring-opening polymerization and the sol-gel reaction of the metal-alkoxide inorganic precursor can be acid catalyzed by the UV degradation of the onium salt. The use of a suitable coupling agent permits to obtain a strictly interconnected network preventing macroscopic phase separation.

Martes, Febrero 14, 2012 - 12:00
Dr. Marco Sangermano
Politecnico di Torino, Italia
Sala 317, CENQUIOR