Mechanical and thermal properties of magnetic tapes and their individual layers strongly affect the tribology of magnetic head-tape interface and reliability of tape drives. Dynamic mechanical analysis, longitudinal creep, lateral creep, Poisson's ratio, the coefficient of hygroscopic expansion (CHE), and the coefficient of thermal expansion (CTE) tests were performed on magnetic tapes, tapes with front coat or back coat removed, substrates (with front and back coats removed), and never-coated virgin films of the substrates. Storage modulus and loss tangent values were obtained at a frequency range from 0.016 to 28 Hz, and at a temperature range from -50 to 150 or 210degreesC. Longitudinal creep tests were performed at 25degreesC/50% RH, 40degreesC/25% RH, and 55degreesC/10% RH for 50 h. The Poisson's ratio and lateral creep were measured at 25degreesC/50% RH. CHE was measured at 25degreesC/15-80% RH. CTE values of various samples were measured at a temperature range from 30 to 70degreesC. The tapes used in this research included two magnetic particle (MP) tapes and two metal evaporated (ME) tapes that were based on poly(ethylene terephthalate) and poly(ethylene naphthalate) substrates. The master curves of storage modulus and creep compliance for these samples were generated for a frequency range from 10(-20) to 10(15) Hz. The effect of tape manufacturing process on the various mechanical properties of substrates was analyzed by comparing the data for the substrates (with front and back coats removed) and the never-coated virgin films. A model based on the rule of mixtures was developed to determine the storage modulus, complex modulus, creep compliance, and CTE for the front coat and back coat of MP and ME tapes. (C) 2004 Wiley Periodicals, Inc.