ENVIRONMENTAL DURABILITY OF PMR-TYPE POLYIMIDE-CLAY NANOCOMPOSITES

摘要

The environmental durability of PMR-15 nanocomposites prepared from an unmodified Layered silicates (LS) and organically modified LS (OLS) have been investigated using an accelerated hydrolytic aging test and a long-term thermo-oxidative aging study. The layered silicates were modified with an amino acid (11-amino-undecanoic acid) and a primary amine (dodecylamine). The nanocomposite prepared using the unmodified LS exhibited higher moisture gain than the neat, while the OLS-containing nanocomposites exhibited lower moisture gains. XRD data of the nanocomposites correlated well with the weight gain data with the PGV/PMR-15 nanocomposite showing the increase in the d-spacing of LS. Dynamic Mechanical Analyzer results showed that the hydrolytic exposure had very little effect on the T_gs of neat resin and nanocomposites. Flexural modulus analysis showed that PGVC10COOH and PGVC12 nanocomposites exhibited more than a 50 percent reduction in the flexural modulus drop off. These results suggested that OLS nanocomposites provides a viable approach to improved 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 used in this study. The poor TOS of the unmodified PGV nanocomposites suggest the presence of impurities, which may be catalyzing the PMR-15 degradation.