Synthesis and characterization of novel aramid-zirconium oxide micro-composites

New micro-composites containing different proportions of zirconium oxide in aromatic polyamide have been prepared via a sol-gel process. Poly(phenyleneterephthalamide) chains with carbonyl chloride end groups were synthesized by reacting a mixture of p- and m-phenylene diamines with terephthaloyl chloride. The chain ends were endcapped with aminophenyltrimethoxysilane. Appropriate amount of zirconium propoxide solution (82.3 wt.%) in propanol was mixed in the polymer solution and then a stoichiometric amount of water was added to the mixture to carry out the hydrolysis of methoxy and propxy groups. Hybrid materials using different proportions of zirconium propoxide in the organic polymer were thus prepared. Thin films cast from this material were transparent, yellow in color and tough. A gradual increase in the tensile strength was observed with increase in the zirconia content (up to 10%). The tensile modulus of the hybrid mixture was in the range of 2.7 to 4.0 GPa at 25°C. The values of the tensile strength varied from 163 to 203 MPa at 25°C. The maximum strain at the break point initially increased but then decreased with further addition of zirconia. The glass transition temperature determined from the maxima of the tan δ data using dynamic mechanical thermal analysis increased with increase in the zirconia content. The thermal decomposition temperature of the hybrid material measured through thermogravimeteric analysis was around 450°C.