Pressure−Volume−Temperature Dependence of Polypropylene/Organoclay Nanocomposites

The pressure−volume−temperature ( PVT ) dependencies of commercial polypropylene melt (PP) and its nanocomposites containing X wt % of organoclay (Cloisite-15A, or C15) and 2 X wt % of a compatibilizer were determined at T = 450−530 K and P = 0.1−190 MPa. C15 was used at concentrations: X = 0, 2, and 4 wt %. Three functionalized PP's were used as compatibilizers: two maleated and one grafted with glycidyl methacrylate. Incorporation of X = 2 wt % C15 into PP resulted in reduction of specific volume by Δ V ≈ 1%, but that of free volume (hole) fraction by Δ h ≈ 5%. The latter quantity was computed from the Simha−Somcynsky lattice−hole equation of state. Furthermore, at constant T and P the hole fraction was found to be linearly related to the bulk-average energetic interaction parameter and to be a sensitive indicator of structural changes. In binary (polymer + organoclay) systems Δ h is linearly related to the interlayer spacing, d 001 . So, where statements from the previous paper are repeated or there are similarities, this is done for purposes of comparison. In three-component systems (with a compatibilizer) the proportionality has been preserved, but large changes of Δ h result in relatively small changes of d 001 . Mechanical properties hardly correlate with either Δ h or d 001, as polymer/compatibilizer morphology and crystallinity complicate the behavior.