Ultrafast synthesis of bentonite-acrylate nanocomposite materials by UV-radiation curing

Nanocomposite materials made of silicate platelets randomly dispersed in a crosslinked polyurethane-acrylate have been readily produced by photoinitiated polymerization. The mineral filler (bentonite) was treated by an ammonium salt or an acrylated amine to make it organophilic and allow the acrylic resin containing a photoinitiator (aromatic ketone) to penetrate into the expanded organoclay galleries. The photoinitiated crosslinking polymerization reaction was followed in real time by infrared spectroscopy and shown to proceed extensively ( 95% conversion) within a few seconds of UV-irradiation. The flat X-ray diffraction spectra recorded with the UV-cured material shows that the layered silicate has been completely exfoliated, thus demonstrating that a nanocomposite material has well been produced. This method of synthesis presents the distinct advantages associated with the UV-curing technology, namely, a solvent-free formulation undergoing ultrafast polymerization at ambient temperature in the presence of air. (C) 2002 Kluwer Academic Publishers.