Preparation and characterization of polyimide nanocomposites with different organo-montmorillonites

초록

Poly(amic acid) nanocomposites were synthesized from a dimethylacetamide (DMAc) solution with two organophilic montmorillonites (organo-MMTs). It was then heated at various temperatures under vacuum, yielding 15-20 um thick films of polyimide/organo-MMT hybrid with different clay contents (1-8 wt%). Dodecylamine (C<inf>12</inf>-) and hexadecylamine (C<inf>16</inf>-) were used as aliphatic alkylamines in organo-MMT. The ultimate strength monotonically increased with increasing clay content in the polymer matrix. Maximum enhancement in the initial modulus was observed for the blends containing 2 wt% clay with two kinds of organo-clays, and values did not alter significantly with further increases in clay content. Additions of only 2 wt% C<inf>12</inf>- and C<inf>16</inf>-MMT to the polyimide were shown to cause 94%-95% reduction in oxygen gas permeability. This is caused by the barrier properties of the clay layers dispersed in the composite. In general, C<inf>16</inf>-MMT is more effective than C<inf>12</inf>-MMT in increasing both the tensile property and the gas barrier in a polyimide matrix. Intercalations of the polymer chains in clay were examined through wide-angle X-ray diffraction (XRD) and electron microscopies (SEM and TEM).