Friction in Magnetic Tapes I: Assessment of Relevant Theory

Publisher Website
Google Scholar
Abstract
A review of friction theories relevant to the interaction between magnetic-recording-device components (hard, inelastic materials) and viscoelastic, polymeric materials used in the manufacture of flexible, magnetic tape is presented. Tabor's classical theory of adhesion with appropriate deformation and shear-strain rates, as well as Hegmon's theory of hysteresis friction, adequately describes the frictional behavior. Other sources of adhesional friction are stiction, meniscus, and microcapillary evacuation. For magnetic-recording-tape applications, the adhesion component of friction is responsible for the major part of the observed friction, except near the softening temperature for the magnetic-coating layer, where the loss tangent becomes very high, or in the case of rough surfaces for which hysteresis friction is significant. From a magnetic-tape design standpoint, the real area of contact (which directly affects adhesional friction) can be minimized by increasing the complex modulus of elasticity of the magnetic layer over the operating temperature range and by increasing the surface roughness. High surface roughness is undesirable from a wear and recording-performance standpoint, therefore, optimization is essential. Creep compliance of the magnetic coating layer, furthermore, should be as low as possible in order to minimize deformation that leads to an increase in the real area of contact for tapes subjected to compressive stresses under tension wound on a reel or against the recording-head surface. In addition, the use of nonpolar materials (which in general possess lower surface energy than polar materials) would lead to reduced friction.