STUDY OF OUT-OF-PLANE ELASTIC PROPERTIES OF PMDA-ODA AND BPDA-PDA POLYIMIDE THIN-FILMS

The out-of-plane elastic moduli of two polyimides, such as Poly(4,4'-o xydiphenylene pyromellitimide) (PMDA-ODA) with flexible chains and pol y(p-phenylene biphenyl tetracarboximide) (BPDA-PDA) with rigid-rod-lik e chains, ranging from 4 to 20 mu m have been investigated using a pre cision capacitance dilatometry with a loading-unloading technique. It is found that the elastic moduli of both polyimides in the out-of-plan e direction are smaller than in the in-plane direction and they are de pendent on the film thickness. In addition, PMDA-ODA is less anisotrop ic than BPDA-PDA. It indicates that the anisotropy in modulus is depen dent on the molecular structure of polyimide. Experimental results sho w that the out-of-plane elastic modulus is correlated to the in-plane molecular orientation and the main chain structure of polyimide. (C) 1 998 Elsevier Science S.A. All rights reserved.