• Chaurand, Perrine
• Bottero, Jean-Yves
• Masion, Armand
• Borschnek, Daniel
• Labille, Jérôme
• Avellan, Astrid
• Scifo, Lorette
• Rose, Jérôme
• Auffan, Melanie
• Bossa, Nathan

Abstract

The study of nanomaterials release from solid matrices is an emerging field of research. Until now most efforts have focused on quantifying and identifying the released objects, providing valuable inputs to risk assessment models. However the mechanisms lying behind release are still largely unknown and rarely investigated. Understanding release mechanisms of nano-objects is critical under two aspects. First of all it may allow predicting NOAA (Nano-objects, their aggregates and agglomerates) release based on a few material properties and may then reduce the need for costly and time-consuming testing. In a second time, unveiling release mechanism is key to implement a safe-by-design approach of nanotechnology. Once elucidated, physico-chemical processes leading to nanomaterial leaching can indeed be counterbalanced, to gain a better control on NOAA emissions. Nanomaterials have wide applications in paint and coating industry. They can improve rheological and mechanical properties of the products, confer them self-cleaning or antimicrobial capacity, or act as UV-absorber, stabilizing agents, pigments, etc. Along their life cycle paint and coatings will however experience processes that may lead to NOAA release. This is especially true for outdoor products, as sunlight and rain can induce very strong degradations. A weathering protocol in climatic chamber was developed at CEREGE, to evaluate NOAA releases from coatings under laboratory conditions. Alternating irradiation under Xe lamp (60W.m-2 in the 300nm-400nm range) and “rain” (=water spraying) phases were applied to an acrylic protective wood coating, enriched with CeO2 nanoparticles. Over a 3-months assay, significant emissions (> 1mg.m-2) of particulate CeO2 into water could be evidenced. A thorough characterization of wood samples was performed in order to understand the mechanisms leading to CeO2 release. Optical microscopy revealed the presence of cracks and blistering on weathered samples. It also showed an increase in paint porosity. In parallel, infrared spectroscopy and nuclear magnetic resonance were used to analyse chemical degradation of the acrylic polymer matrix. The overall distribution of CeO2 nanoparticles in the coating was assessed from results of X-ray fluorescence microscopy and laser-ablation-ICP-MS. Complementarily, direct size measurements on CeO2 aggregates incorporated in the wood coating were performed by micro and nano X-ray computed-tomography. They proved that aggregation of nanomaterials took place upon aging. Further transformation of ceria nanoparticles within the coating was evidenced by XANES, which showed partial reduction Ce(IV) to Ce(III) along the experiment. Based on this data, hypothesis on both the processes lying behind release and the form under which CeO2 is released is presented.into mechanisms leading to the release of ceo2 nanoparticles embedded in an acrylic wood coating

Topics

• nanoparticle
• impedance spectroscopy
• polymer
• phase
• experiment
• tomography
• crack
• leaching
• aging
• porosity
• wood
• aging
• infrared spectroscopy
• fluorescence microscopy
• inductively coupled plasma mass spectrometry