Surface modification of calcium carbonate nanofillers by fluoro- and alkyl-alkoxysilane: Consequences on the morphology, thermal stability and gas barrier properties of polyvinylidene fluoride nanocomposites

Nano-sized precipitated silica coated calcium carbonate fillers (PCC-Si) were modified by an alkyl- and a fluoro-alkoxysilane derivative, respectively. PCC-Si surface modification was characterized by elemental analysis, Fourier transform infrared analysis and X-ray photoelectron spectroscopy. The modification conditions used for surface treatment led to a similar grafting density (around 3.2 μmol m−2) for the two alkoxysilane derivatives. A significant decrease of filler hydrophilicity was observed after the alkoxysilane treatment. Nanocomposites prepared by melt mixing the modified fillers (10 wt.%) with polyvinylidene fluoride (PVDF) depicted no color change, an enhanced filler dispersion state with an homogeneous dispersion of very small filler aggregates (less than 150 nm diameter size), an increase of the thermal stability at high temperature and no change of the PVDF crystalline morphology. The oxygen permeability decrease measured on the nanocomposite prepared from the perfluorooctyltriethoxysilane modified filler was in good agreement with Maxwell law. The permeability increase evidenced for the nanocomposite based on the octyltriethoxysilane modified PCC suggested the formation of weak interfaces in this system.

Graphical abstractNanofiller dispersion state as observed at the TEM scale for PVDF/PCC-F (Nano-sized precipitated calcium carbonate fillers (PCC) modified by the perfluorooctyltriethoxysilane).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Alkoxysilane modified precipitated calcium carbonate filler characterization. ► Influence of the filler modification on the nanocomposite morphology. ► Role of the nanofillers on thermal stability and barrier properties.