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Abstract
An experimental technique to measure creep properties in compression of thin polymeric film is developed. An analysis is derived to calculate creep compliance and elastic and creep strains in compression of the thin films. Measurements were made on five typical magnetic inks and the poly (ethylene terephthalate) substrate used in magnetic tapes. Modulus of inks as measured by the developed technique is an order of magnitude lower than the bulk modulus measured by other techniques. This indicates that the ink-film surface is mechanically different from that of the bulk of the film. No significant changes in mechanical properties between film surface and bulk were seen in the case of PET films. Calendered magnetic inks showed slightly lower creep compliance than uncalendered films. Recovery experiments showed that the ink surface goes through some permanent deformation which would affect tape friction.
Magnetic tapes under compression against a smooth surface, such as found at the hub of conventional tape reels, exhibit changes in friction due to creep. This phenomenon can be accelerated by temperature and humidity. Friction measurements were made on un-backcoated magnetic tapes at end of tape (EOT), wound on a spool, as received and after accelerated aging. Tapes having high creep compliance exhibited high friction after aging. Thus, measurements of creep compliance can predict friction at EOT after aging.
Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984
Notes
Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984