Richard L. Bradshaw

Friction in Magnetic Tapes III: Role of Chemical Properties

Whenever there are changes in surface chemistry of the magnetic tape caused by various tribological or environmental parameters, such as humidity and temperature, they may significanty increase the adhesive interaction between the magnetic tape and the drive components. Exposure to high humidity at elevated temperatures for extended periods can result in the hydrolytic degradation of the tape-binder system. The products of hydrolytic degradation have lower molecular weight and may be tacky in nature. Changes in the binder can be monitored by measuring molecular weight, extractable binder-to-lubricant ratio, and modulus of elasticity. A chemically stable binder system minimizes the risk of high friction. In the case of tapes tested at low humidity, the frictional behavior shows little dependence on the chemistry of the binder and primarily on the thermomechanical response of the magnetic coating. It is also noted that in most commercial tapes, the friction is high when measured at high humidities (above 60...

Friction in Magnetic Tapes I: Assessment of Relevant Theory

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. Tabors classical theory of adhesion with appropriate deformation and shear-strain rates, as well as Hegmons 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 t...

Fifty years of IBM innovation with information storage on magnetic tape

On May 21, 1952, the International Business Machines Corporation announced the IBM Model 726 Tape Unit with the IBM Model 701 Defense Calculator, marking the transition from punched-card storage to digital storage on flexible magnetic tape. That bold introduction was the beginning of what is now a 50-year history of invention that has seen remarkable advances in the storage of information on flexible magnetic ribbons ten times thinner than a human hair and capable of storing more than 100000 times more data in the same volume as the first reel of tape introduced in 1952. This historical perspective is dedicated to the people who made that first tape drive possible and to those who continue that tradition in the Removable Media Storage Solutions (RMSS) team of the International Business Machines Corporation Tape Development Laboratory, headquartered in Tucson, Arizona.