Study of the effect of organically functionalized silica nanoparticles on the properties of UV curable acrylic coatings

In this work the properties of UV curable coatings were improved modifying the polymeric matrix adding properly functionalized silica inorganic nanoparticles. Mild steel sheets were used as substrate. Pre-formed silica nanoparticles, prepared by sol–gel chemistry from methyltriethoxysilane (MTES) and methacryloxypropyltrimethoxysilane (MPTMS) precursors, were dispersed into UV curable acrylic oligomers: by irradiation a polymeric matrix embedding the nanoparticles was obtained. Unfilled UV cured coatings were also produced for comparison. The DSC measurements revealed different thermal stabilities among the samples, depending on the presence of the functionalized nanoparticles. The barrier properties (investigated by means of electrochemical impedance spectroscopy, EIS) were demonstrated to be strongly affected by the presence of the nanoparticles. In particular, a proper functionalization of the silica nanoparticles leads to noticeable improvement of the barrier properties of the coatings against ions permeation. The effect of the functionalized nanoparticles on the coating properties was also investigated performing water vapor diffusion measurements through the different coatings. The experimental measurements highlighted that the appropriate functionalization of the silica particles leads to noticeable improvements of the barrier properties against water and ions permeation of the composite polymeric coating with respect to the unfilled UV curable resin.

Research highlights
► Barrier properties of acrylic coatings improved by adding silica nanoparticles.
► Importance of chemical modification of the silica particles with modified silanes.
► Balance between the amount of MTES and MPTMS precursors affects final properties.
► The presence of the MMp 25 particles improves the ions barrier properties.