Preparation and characterization of UV-cured acrylic nanocomposites based on modified organophilic montmorillonites

UV-cured nanocomposites have been prepared through the photopolymerization of the acrylic resin BEMA (Bisphenol A ethoxylate dimethacrylate) added with organophifilic montmorillonites. Two types of commercially available nanoclays namely Cloisite 30B and Cloisite Na⁺ were further modified with organic compatibilizers (dodecylsuccinic anhydride, octadecylamine, octadecanoic alcohol and octadecanoic acid) in order to increase their basal spacing and improve the dispersion in the acrylic matrix. The modification with the organic compatibilizers determined an increase of the interlayer distance, as revealed by XRD (X-Ray Diffraction) analysis. The different types of the modified nanoclays were then dispersed in BEMA monomer at 5% m/m concentration and UV-cured in order to prepare the nanocomposites. XRD measurements performed on the nanocomposites showed a slight increase of the interlayer distance indicating the formation of intercalated structures. The photopolymerization reaction was monitored through real-time FT-IR (Fourier Transform Infrared Spectroscopy) in order to check any influence of the nanofillers on the cure kinetics. The nanocomposites were investigated by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetric) analyses and compared to the neat UV-cured resin. The presence of the nanofillers did not influence the glass transition temperature (T_g) of the acrylic resin; in addition an increase of the thermal stability in air of the nanocomposites was evidenced through TG analysis.