Long‐term mechanical and viscoelastic behavior of constitutive polymeric materials used for magnetic tapes

Abstract

AbstractCreep‐compliance behavior of specially prepared magnetic tape materials was measured at elevated temperature levels to facilitate the use of a time–temperature superposition (TTS) process. This TTS process allowed for the construction of master curves at a reference temperature of 30°C, which were used to predict the long‐term viscoelastic behavior of the magnetic particle (MP) and metal‐evaporated (ME) tapes used in the study. The specially prepared samples allowed for the use of a rule of mixtures technique to determine the long‐term creep compliance of the front coat and back coat used for the magnetic tapes. To test the validity of this procedure, the front coat, substrate, and back coat data determined through separate experiments were used to calculate creep compliances of simulated tapes. These calculated creep‐compliance curves were then compared to measured data for the actual magnetic tapes. After determination and validation of the front coat, substrate, and back coat creep‐compliance data sets, they were used to determine strain distributions when the tapes are stored in a reel. Strain distributions were calculated for two cases, which reflect how tapes are stored in different drives: (1) the front coat (magnetic + nonmagnetic layer) is oriented away from the hub, and (2) the front coat is oriented toward the hub. Results showed that strain in the critical front coat of a tape is lower if it is stored with the front coat oriented toward the hub. In addition, the use of the creep‐compliance data showed that the MP tape front coat is more susceptible to creep than the ME tape front coat. The strain distributions in future magnetic tapes were also simulated by reducing the thickness and compliance of the layers. Results showed the importance of using lower compliance front coat, substrate, and back coat materials if thinner tapes are to be developed to increase the volume of information that can be stored in a magnetic tape reel. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1142–1160, 2001