The annual production of single-use plastic is close to 400 million tons. The thermosetting plastics in contrast to thermoplastics is challenging for disposal due to its non-reusable nature. The thermosets have complex cross-linking monomer units which make them hard and undissolvable. It is the mechanical strength, three- dimensional stability, thermal and chemical resistance that makes them applicable to areas like automotive, electronics and industries. Hence thermosets can be the ideal polymers for production. However thermosets have a major disadvantage, it cannot be recycled. Thus thermosets usually end up in landfills.
The researchers of Case Western Reserve University in Cleveland lead by Ica Manas-Zloczower, Distinguished University Professor developed a new process that produces vitrimers that are recyclable from non-recyclable thermoset polymers.
The Process in Detail.
The researchers coined the term “vitrimerization” – a process in which the permanently linked networks are converted into dynamic networks by infusing a suitable catalyst changing them into vitrimers. A transesterification reaction was selected for the process. The ester group and the free hydroxyl groups can be infused with a catalyst that enables transesterification thus forming vetrimers. Epoxy and Polyurethane thermosets were undergone vitrimerization to study its recyclability. The catalyst used for infusion is tin (II) 2-ethyl hexanoate (Sn(Oct)2) due to its high catalytic ability and stability in transesterification reactions. The process works best in a temperature higher than the glass transition temperature (Tg) of the polymer.
The resultant vitrimers formed can be processed by extrusion, compression and injection molding. Multiple recycling of virtrimerized polymer samples are also tested and can be reprocessed upto two times (the third recycling resulted in a paste). Various tensile and thermal testing proved to have a decrease in the mechanical properties from the original polymer. This can be made better by addition of fillers like carbon nanotubes using extrusion with vitrimers. The resultant nanocomposite shows the same or higher properties than the original material.
In conclusion, this is a cost-efficient, eco-friendly technique that will provide new insight into the recycling of thermosetting plastics.
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Great Article. Interesting Read
Interesting article. Keep writing.
I always had a bit of curiosity on this topic, if it is possible to create a perfect plastic which doesn’t harm our Mother Nature but still is stable and sturdy for everyday use, looks like it’s closer than I would have guessed.
Thank you for this wonderful article Mr.Sharath, needed this bit of optimism during this times.
Very informative