Fire and Gas Barrier Properties of Poly(styrene-co-acrylonitrile) Nanocomposites Using Polycaprolactone/Clay Nanohybrid Based-Masterbatch

Exfoliated nanocomposites are prepared by dispersion of poly(ε-caprolactone) (PCL) grafted montmorillonite nanohybrids used as masterbatches in poly(styrene-co-acrylonitrile) (SAN). The PCL-grafted clay nanohybrids with high inorganic content are synthesized by in situ intercalative ring-opening polymerization of ε-caprolactone between silicate layers organomodified by alkylammonium cations bearing two hydroxyl functions. The polymerization is initiated by tin alcoholate species derived from the exchange reaction of tin(II) bis(2-ethylhexanoate) with the hydroxyl groups borne by the ammonium cations that organomodified the clay. These highly filled PCL nanocomposites (25 wt% in inorganics) are dispersed as masterbatches in commercial poly(styrene-co-acrylonitrile) by melt blending. SAN-based nanocomposites containing 3 wt% of inorganics are accordingly prepared. The direct blend of SAN/organomodified clay is also prepared for sake of comparison. The clay dispersion is characterized by wide-angle X-ray diffraction (WAXD), atomic force microscopy (AFM), and solid state NMR spectroscopy measurements. The thermal properties are studied by thermogravimetric analysis. The flame retardancy and gas barrier resistance properties of nanocomposites are discussed both as a function of the clay dispersion and of the matrix/clay interaction