Advanced Characterization of Silica–Encapsulated Aluminum Pigments

  • Draga Dragnea AlbaAluminiu LTD., Str. Gării 6, 516100 Zlatna, Alba, Romania; Department of Chemical and Biochemical Engineering, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Str. Gh. Polizu 1-7, 011061 Bucharest, Romania
  • Dragos Gudovan Department of Chemical and Biochemical Engineering, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Str. Gh. Polizu 1-7, 011061 Bucharest, Romania https://orcid.org/0000-0003-4442-4000
  • Elena Zaharia Department of Chemical and Biochemical Engineering, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Str. Gh. Polizu 1-7, 011061 Bucharest, Romania
  • Ion Dragnea AlbaAluminiu LTD., Str. Gării 6, 516100 Zlatna, Alba, Romania
  • Costin Sorin Bildea Department of Chemical and Biochemical Engineering, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Str. Gh. Polizu 1-7, 011061 Bucharest, Romania http://orcid.org/0000-0001-7707-1366

Abstract

For environmental reasons, the paints industry shifts from solvent-borne towards water-borne formulations. This change is challenging the business of aluminum pigments, as the hydrogen released by the reaction of aluminum with water degrades the optical properties, besides being a safety concern. In this work, industrial-grade aluminum pigments are encapsulated, by a well-known method, in a silica matrix by sol-gel process using isopropanol - a more suitable solvent for the industry. The effectiveness of the encapsulation process is proven by advanced physical methods (Scanning Electron Microscopy, Energy Dispersive X-Ray Analysis, Selected Area Electron Diffraction, Fourier Transformed InfraRed Spectroscopy, Thermo-Gravimetric Analysis) and by industry-relevant tests (stability in water, hiding power, flop and granulometry). Moreover, advanced surface-applied physical methods (High Resolution Transmission Electron Microscopy combined with Selected Area Electron Diffraction and Scanning Transmission Electron Microscopy, and FT-IR microscopy) clearly show the homogeneity of the resulting pigments, a quality which is highly desirable for practical applications. The results demonstrate that stability comparable to that of pigments passivized by chromium-based inhibitors is easily achieved, for a variety of operating conditions. However, accomplishing a homogeneous silica layer of the right thickness is the determining factor for good optical properties.

Keywords: water-borne coatings, Aluminum Pigments, sol-gel process, physical characterization, stability
Published online
2019-11-28
How to Cite
Dragnea, D., Gudovan, D., Zaharia, E., Dragnea, I. and Bildea, C. S. (FIRST) “Advanced Characterization of Silica–Encapsulated Aluminum Pigments”, Periodica Polytechnica Chemical Engineering. doi: https://doi.org/10.3311/PPch.14371.
Section
Articles