A Study of the Mechanical Behavior of Polyimides

The mechanical properties of four different polyimide samples are measured. H-film, poly(N,N'-( p,p'-oxydiphenylene)pyromellitimide), shows no softening phenomena below 500°C. The three other polyimides exhibit a definite softening at elevated temperatures. All of the samples investigated show evidence of chemical reaction and eventual deRrada tion taking place above 400°C. While x-ray techniques show H-film to be slightly crystalline, the other polyimides display typical amorphous scattering patterns. Annealing raises the softening temperature and induces crystallinity in one of the samples. Factors such as the purity of starting materials and the complete conversion to polyimide linkage must be considered when comparing the mechanical properties of these various polyimides.