Enhanced Gas Barrier and Thermal Properties of Polyimide/Montmorillonite Nanocomposites as a Result of "Dual-Plane" Structure Effect

A type of highly exfoliated, dispersed, and oriented organic montmorillonite filled polyimide (DABPI/OMMT) nanocomposites has been prepared successfully via in situ polymerization. Compared with the pristine DABPI, the DABPI/OMMT nanocomposites exhibit much better barrier and thermal performance. The water vapor permeability and oxygen permeability of DABPI/OMMT (5 wt%,) are low to 0.31 g mil M-2 day(-1) and 0.72 cm(3) mil m(-2) day(-1), respectively. Meanwhile, its 5% weight-loss temperature and coefficient of thermal expansion are 568 degrees C and -1.1 ppm K-1, respectively. The results of transmission electron microscopy, 1D and 2D wide angle X-ray diffractograms, as well as positron annihilation lifetime spectroscopy reveal that the excellent barrier and thermal performance of DABPI/OMMT (5 wt%) are mainly because of the high orientation of OMMT, increased crystallinity and low free volume of DABPI matrix. These are resulted from the "dual-plane" structure effect, which is the synergistic orientation effect between the rigid planar molecular chains of DABPI and nanoplatelets of OMMT. (C) 2017 Society of Plastics Engineers