An alkali treatment under various operating conditions is conducted on a commercial anion-exchange membrane containing poly(vinyl chloride) (PVC) as a backing and binder to study the effect of the treatment on the mechanical properties by both Müllen burst and tensile tests. Contrary to our expectations, the Müllen burst pressure and tensile strain at break improved significantly after the alkali treatment in comparison to the pristine membrane and then decreased as the treatment period progressed. A good correlation is observed between the area below the stress-strain curve and burst pressure. To understand the obtained results, the PVC degradates are recovered by Soxhlet extraction and characterized via nuclear magnetic resonance and gel permeation chromatography. It is discovered that the PVC main chains degraded in the alkali solution. We propose a composite model to explain the burst pressure improvement mechanism by the change in the chemical structure of the PVC binder.
Keywords: alkali; anion-exchange membrane; cleaning in place; degradation; dehydrochlorination; mechanical properties; polyvinyl chloride.