Greenville, South Carolina – Lignin, a complex aromatic polymer that provides structure to plants, can be used to make polyols for polyurethane. However, its heterogeneous structure makes recycling lignin-based polyurethane a challenge, and a team at Clemson University has been looking for a way to do this.
Lignin makes up between about 15 and 40% of woody biomass, and thus is widely available in waste such as timber and sawdust. It is therefore an appealing bio-based source as a starting material for biobased synthetic polymers such as polyurethane.
However, recycling is difficult as lignin has such a heterogeneous structure, and its reactivity adds to the challenge. The Clemson group has found a way to achieve chemical recycling that retains the lignin’s functionality, allowing it to be used to make more non-iso PU.
The high-pressure hydrolysis process added an ethylene glycol moiety into the lignin’s side-chain region, increasing its hydroxyl content and solubility. They speculate that the closed loop recycling process could have potential in creating a circular economy for the PU.
The work has been published in the journal Nature Sustainability.