Aging of magnetic recording tape

Almost all commercial magnetic recording tapes are manufactured employing a polyester urethane elastomer as the oxide binder and also as the backcoat binder on backcoated tapes. For temperature excursions encountered for ordinary tape use and storage, polyester urethanes as a general class of materials are typically susceptible to environmental degradation by hydrolysis: a chemical reaction between these materials and atmospheric water vapor. Extensive hydrolytic degradation can lead to the generation of sticky and gummy chemical products. It can be anticipated that a substantial contribution to environmental tape aging and performance characteristics might derive from the chemical behavior of ester hydrolysis. The environmental aging of a commercial magnetic recording tape was experimentally investigated, and it was found that the primary mechanism of tape aging and degradation resulted from hydrolysis of its polyester urethane binder. The chemical reaction is additionally reversible, a property which suggests a methodology for restoring and rejuvenating environmentally degraded tapes. Being a reversible reaction, there exists environmental conditions of relative humidity and temperatures which are ideal for long-term archival preservation. For the tape of this study, 24-percent relative humidity (RH) at room temperature was identified as its ideal storage humidity. This study may have significance for many industrial and government specifications which call out assorted qualifying tests involving tape exposure or tape operations at extremes of humidity and temperature. It is suggested from the findings of this work that such tests may measure and monitor the various manifestations of hydrolysis, which may bear little if any relationship to tape use at moderate ambient conditions or in hermetic environments. The results of this work further indicate that hermetic sealing of a tape may allow operations to higher temperatures than possible in air, with the upper temperature limit determined by lubricant boil-out or thermal degradation (pyrolysis) of the polymers.