Environmental durability of polymerization of monomer reactants-type polyimide-clay nanocomposites

The environmental durability of PMR-15 nanocomposites prepared from an unmodified Na+-montmorillonite (PGV) and two organically modified PGV (PGVC10COOH, PGVC12) have been investigated using an accelerated hydrolytic aging test and a long-term thermo-oxidative aging study. PGV was modified with an amino acid (11-amino-undecanoic acid) and a primary amine (dodecylamine). The PGV/PMR-15 nanocomposite exhibited higher moisture gain than the neat resin, while PGVC10COOH, PGVC12/PMR-15 nanocomposites exhibited lower moisture gains. XRD data of the nanocomposites correlated well with the moisture gain data for the nanocomposites. PGVC10COOH and PGVC12/PMR-15 nanocomposites exhibited more than a 50% reduction in the flexural modulus drop off. These results suggest that nanocomposites provide a viable approach in decreasing the susceptibility of PMR-15 to hydrolytic degradation. No improvement in the thermal oxidative stability of the nanocomposites was achieved. This may be attributable to the relatively low thermal stability of the organic modifiers and/or the presence of impurities, which catalyzed the PMR-15 degradation.