Friction Transition In Polyimide Films as Related to Molecular Relaxations and Structure.
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER
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The friction characteristics of polyimide films bonded to metallic substrates were studied from 25 C to 500 C. These results were correlated to molecular structure and the results of torsional braid analysis TBA. A large friction transition 0. 23 to 0.03 was found to occur at 45 C OR - 5 C. It was postulated that this transition was initiated by some molecular relaxation, which gave the molecules a degree of freedom by which an external mechanical stress could rearrange the molecules into a structure, such as an extended chain, which is conducive to easy shear. Above 300 C the friction characteristics were found to be dependent on the thermal prehistory of the film. MM
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