Out-of-plane thermal expansion coefficient of biphenyldianhydride-phenylenediamine polyimide film

The out-of-plane thermal expansion coefficient α⊥ of biphenyldianhydride-phenylenediamine (BPDA-PDA) polyimide thin film between 20 and 400°C has been measured using a laser spot scanning interferometer. The α⊥ varies from 100 ppm/°C at 20°C to 400 ppm/°C at 400°C. As the result of highly anisotropic microstructure, the α⊥ is much larger than the in-plane thermal expansion coefficient α∥ and increases dramatically when the temperature exceeds the glass transition temperature (≈320°C). © 1993 The Minerals, Metals & Materials Society.