Strength properties of separators in alkaline solutions

Cellulose-based separators have been used in alkaline battery systems for many years. In particular, Ag-Zn systems have used cellophane and fiber-reinforced regenerated cellulose manufactured via the viscose process as the main separator. There has been a reported decrease in the shelf-life of Ag-Zn batteries. One of the believed causes is degradation of the cellulosic separator by the alkaline solution (40% KOH) that is used as the electrolyte. Battery separator nonwovens that were coated with regenerated cellulose via the viscose process were subjected to storage in 40% potassium hydroxide (KOH) over a two month period. Samples were periodically checked for wet MD tensile strength. The test showed that among the nonwovens, the polyamide retained about 93% of its initial tensile strength whereas polyvinyl alcohol and cellulosic nonwovens retained only 55% and 35%, respectively. Adding a viscose coating to the nonwovens improved tensile strength retention by 20-25% for the polyvinyl alcohol and cellulosic materials. The viscose-coated polyamide retained more than 98% of its initial tensile strength