Understanding of the mechanisms leading to the release of nanoparticles in paint : towards a safe by design approach

J.F. Damlencourt
CEA Grenoble/PNS,
France

Keywords: nanoparticles, release

Summary:

Nanotechnology offers the capability to produce materials with novel functionalities and improved characteristics such as higher durability, fire resistance, thermal stability, self-cleaning, and photocatalytic properties. The addition of nanoparticles in paint modifies their formulations and leads to an improvement of their mechanical properties, their UV resistance but also their rheological properties and their colors for example. Titanium dioxide (TiO2) particles, at the micron-scale, was usually used to provide a white color whereas at the nano-scale, it is mainly used for its an efficient photocatalytic effect to purify the environment. Nano-TiO2 are then incorporated both in outdoor and indoor construction materials (bitumen, tiles, paints). Concerning outdoor applications, the release of TiO2 nanoparticles from buildings paint into aquatic environment has been evidenced by many authors. Several physico-chemical parameters of two photocatalytic micro and nano-TiO2 based- paints was investigated, before and after climatic ageing to understand phenomena that govern the release of TiO2 particles in photocatalytic paints. TiO2 powders, dispersion and paints (either in liquid form or applied on a substrate) were well characterized to determine their chemical natures, particle size distributions, particle shapes and dispersion state with Scanning Electron Microscopy coupled with Energy Dispersive Spectrometry (SEM-EDS), Cryogenic Transmission Electron Microscopy (cryo-TEM), TEM, X-Ray Diffraction (DRX), X-Ray Photoelectron Spectrometry (XPS), Tomography X3D, but also by Small Angle X-Ray Scattering (SAXS) and Small Angle Neutron Scattering (SANS). Painted panels were then exposed to accelerated weathering experiments respecting the norm EN ISO 16474-3 to assess the impact of ageing on polymeric matrices degradation. All these experiments allowed us to analyze the surface and the bulk of each samples and to understand the weathering effect on paints, its impact on nanoparticles release and on the interface between polymer and pigments. The good understanding of mechanisms leading to the NP release allowed us to go on safe by design aspects.