Effect of montmorillonite on thermal and moisture absorption properties ofpolyimide of different chemical structures

The thermal properties and the moisture absorption of three types of polyim ide/montmorillonite nanocomposite were investigated: 3,3 ' ,4,4 ' -biphenyl tetracarboxylic dianhydride-4,4 ' -oxydianiline (BPDA-ODA); pyromellitic d ianhydride-ODA (PMDA-ODA); and 3,3 ' ,4,' -benzophenone tetracarboxylic dia nhydride-ODA (BTDA-ODA). The inhibition effect on in-plane coefficients of thermal expansion (CTE) and moisture absorption of these polyimide nanocomp osites by layered silicates from montmorillonite was found to decrease with the crystallinity in the pristine polyimides. The largest reduction, 30% i n in-plane CTE occurred in the case of amorphous BTDA-ODA containing 5 wt % montmorillonite as compared with that of pure BTDA-ODA, while the reductio n in in-plane CTE was 20% for the case of semicrystalline BPDA-ODA. The max imum reduction in moisture absorption, 43%, also took place for the case of 3/97 ODA-Mont/BTDA-ODA as compared with that of pure BTDA-ODA, whereas the semicrystalline 1/99 PPD-Mont/BPDA-ODA showed a 30% reduction as compared with that of pure BPDA-ODA. (C) 2001 John Wiley & Sons, Inc.