The tribological and dynamic behavior of alternative magnetic tape substrates

Tribological characteristics of alternative magnetic tape substrates are presented along with dynamic mechanical measurements of their viscoelastic behavior. The polymeric substrates analyzed include the current industrial standard PET, and four alternative substrates PEN, ARAMID, PI, and PBO. Surface roughness characteristics obtained using an atomic force microscope (AFM) show that the alternative substrates are smoother than PET because anti-slip agents are probably not present in these newer materials. Based on macro-scale friction measurements using a reciprocating friction apparatus, the friction coefficient for a PET substrate rubbing against a ferrite surface is less than that measured for PEN, ARAMID, or PBO. However, the anti-slip agents present in PET lead to an increase in friction when it is rubbed against itself or a metal-particle tape. This trend was not observed for the alternative substrates. From the dynamic mechanical analysis, the storage (or elastic) modulus E' was obtained as a function of temperature and frequency along with the loss tangent, tan delta. Frequencytemperature superposition was used to predict the dynamic mechanical behavior of the substrates over a 10-12 decade frequency range. Results show that PEN, ARAMID, and PBO have a higher storage modulus than PET or PI over this frequency range, and PET will undergo more nonrecoverable deformation at frequencies above 100 Hz. The relationship between modulus data and head wear is discussed in terms of tape-to-head conformity, and a method is presented for predicting the deformation strain on a tape when it is subjected to a transient deformation from the head.