Thermal properties and flammability of acrylic nanocomposites based upon organophilic layered silicates

Thermal and mechanical properties of poly(methylmethacrylale-co-dodecylmethacrylate) nanocomposites based upon exfoliated organophilic layered silicates, were investigated as a function of the silicate and comonomer content. Layered silicates such as sodium bentonite were rendered organophilic by means of ion-exchanging sodium cations for N,N,N,N-dioctadecyl-dimethyl-ammonium cations. Silicate exfoliation was enhanced by means of 5 and 10 wt.-% dodecyl-methacrylate (LMA) addition to afford translucent reinforced acrylic nanocomposites. In contrast to conventional filled acrylic polymers, only 10 wt.-% organophilic silicate was sufficient to increase Young's modulus from 2200 to 4030 MPa, glass temperature from 72 to 80 degrees C and degradation temperature from 220 to 256 degrees C with respect to the neat MMA/LMA (90 wt.-% /10 wt.%) copolymer. Flammability studies, performed on a cone calorimeter, revealed that the maximum heat release rate of MMA/LMA copolymer nanocomposite decreased from 837 kW/m(2) to 566 kW/m(2). The nanocomposite morphology was examined by means of transmission electron microscopy (TEM).