Superabsorbers based on crosslinked sodium polyacrylate polymers cannot be easily recycled, resulting in 2 million tons of superabsorbers being landfilled or burned every year. A fast and efficient strategy to recycle superabsorbers would significantly alleviate environmental pollution and promote a sustainable use of these polymers. Herein, the rapid recycling of crosslinked sodium polyacrylate hydrogels based on their inherent UV degradation is demonstrated without the need for chemicals besides water. A quantitative conversion of crosslinked sodium polyacrylate into soluble sodium polyacrylate is achieved in minutes, almost 200 times faster than a previous approach based on de-esterification. The obtained soluble sodium polyacrylate can be used, for example, as a thickener for aqueous dyes or can be esterified with n-butanol or 2-ethylhexanol to serve as a pressure-sensitive adhesive. The UV photodegradation and esterification of superabsorbers is fast, scalable, safe, and economical and yields polymers with controllable molecular weight in the range of 100-400 kg/mol. It thus offers distinct advantages over the chemical de-crosslinking strategies presented previously.
Keywords: UV degradation; hydrogels; polyacrylates; pressure-sensitive adhesives; recycling; superabsorbers; thickeners.