Preparation and properties of polyamide–titania nanocomposites

Transparent poly(trimethylhexamethyleneterephthalamide) based titania nanocomposites were prepared by the in-situ generation of inorganic network structure via the sol-gel process. Different concentrations of tetrapropylorthotitanate (TPOT) were added to the polyamide solution dissolved in anhydrous dimethylforamide (DMF). After thorough mixing, TPOT was hydrolyzed and condensed to produce titania network in the matrix using diethylamine as catalyst. Thin and transparent composite films with various amounts of titania were cast by solvent elution technique. These films were subjected for their optical, mechanical, thermal and morphological analyses. Tensile strength of the films was found to increase with increase in titania concentration relative to pure polymer and maximum strength was obtained for 5–wt% titania, but elongation at break was observed to decrease sharply on addition of titania. Dynamic mechanical thermal analysis (DMTA) carried out on the samples showed a systematic increase in the glass transition temperature, i.e., 101 °C with pure polyamide to 155 °C with composites containing 10-wt% titania contents. The storage modulus was also found to increase with increase in titania contents in the matrix. The decrease in the storage modulus of the hybrids with rise in temperature was observed to be much smaller as compared to that of pure polymer. Thermal decomposition temperatures of the hybrids were found in the range of 450–500 °C. The weights of the residues left at 700 °C were nearly proportional to the titania contents in the original hybrids. SEM observations indicated titania network structure dispersion at nanometer-level in the matrix.