Polyamide-silica nanocomposites: mechanical, morphological and thermomechanical investigations

BACKGROUND: The physical properties of polyamides can be enhanced through incorporation of inorganic micro- and nanofillers such as silica nanoparticles. Transparent sol-gel-derived organic-inorganic nanocomposites were successfully prepared by in situ incorporation of a silica network into poly(trimethylhexamethylene terephthalamide) using diethylamine as catalyst. Thin films containing various proportions of inorganic network obtained by evaporating the solvent were characterized using mechanical, dynamic mechanical thermal and morphological analyses. RESULTS: Tensile measurements indicate that modulus as well as stress at yield and at break point improved while elongation at break and toughness decreased for the hybrid materials. The maximum value of stress at yield point (72MPa) was observed with 10 wt% silica while the maximum stress at break point increased up to 66 MPa with 20 wt% silica relative to that of pure polyamide (44 MPa). Tensile modulus was found to increase up to 2.59 GPa with 10 wt% silica in the matrix. The glass transition temperature and the storage moduli increased with increasing silica content. The maximum increase in the T-g value (144 degrees C) was observed with 20 wt% silica. Scanning electron microscopy investigation gave the distribution of silica, with an average particle size ranging from 3 to 24 nm. CONCLUSION: These results demonstrate that nanocomposites with high mechanical strength can be prepared through a sol-gel process. The increase in the T, values suggests better cohesion between the two phases, and the morphological results describe a uniform dispersion of silica particles in the polymer matrix at the nanoscale. (C) 2007 Society of Chemical Industry.