TAGS: Sustainability / Natural Adhesives UV/EB Cure Adhesives
Researchers at the Karlsruhe Institute of Technology (KIT) have now significantly improved the complex recycling of superabsorbent disposable diapers. Using UV rays, they dissolve the chemical chains that hold the polymers together 200 times faster than before, without chemicals and at room temperature. The dissolved polymers can be processed into new adhesives and dyes.
Sustainable Solution for Hygiene and Medical Products
Superabsorbents are not only found in diapers, but also in numerous other hygiene and medical products such as sanitary napkins or bandages. Until now, anyone who wanted to reuse their chemical core had to use strong acids because the absorbent material is made of sodium polyacrylate. These cross-linked polymers are insoluble in water and cannot be melted even at high temperatures - they only decompose.
However, the acids were able to “cut” the chains that make the polymers stable at 80 degrees Celsius and after about 16 hours, thus enabling recycling. However, the process is complex and expensive, which means that the reuse of superabsorbents is rare. Every year around two million tons of it end up in the trash or are burned.
Solid to Liquid in Five Minutes
Researchers from the Institute of Biological and Chemical Systems, the Institute of Biological Interfaces and the Institute of Technical Chemistry and Polymer Chemistry at KIT have now discovered that the cross-linked polymers made of sodium polyacrylate dissolve after absorbing water under UV light.
“
The chains that connect the polymers are refracted by light and are then so loose that they float in the water and become liquid fibers,” explains Pavel Levkin, professor at the Institute of Biological and Chemical Systems. To do this, the researchers cut out the absorbent pad from conventional diapers, moistened it with water and then exposed it to light with a 1000-watt lamp. After just five minutes, the solid material turned into a liquid that dripped into a collecting container.
Recycled Polymers can be Used in Various Ways
The team then processed the liquid raw chemical into new adhesives and dyes using known processes. “
It was important to observe that the substance is soluble and processable. We can certainly do a lot more with this,” explains the scientist.
Clean diapers were used for the tests. In practice, however, it is possible to filter out superabsorbents from contaminated materials. “
So nothing stands in the way of a realistic application,” says Levkin.
In addition, the recycling process can be optimized cost-neutrally and ecologically using solar power. “
We have found a future-oriented strategy for reusing superabsorbents. This could significantly reduce environmental pollution and contribute to a more sustainable use of polymers.”
Source: Karlsruhe Institute of Technology (KIT)