Greenville, South Carolina – The US Environmental Protection Agency has given one of the 2021 Green Chemistry awards to a recyclable non-iso PU foam made from lignin. The foam was developed by Srikanth Pilla and his team in Clemson University’s department of automotive engineering.
Lignin, a waste product from wood processing, has been used in the manufacture of PU in the past, but in the form of polyols that are reacted with diisocyanates. This foam involves no isocyanates, and has been shown via radiocarbon analysis to be 100% biobased.
‘The goal was to create a polyurethane foam using lignin but using an approach that is different to what others have done and yet make it sustainable and 100% biobased,’ Pilla said. ‘The outcome is what won this award. It’s truly remarkable green chemistry to make non-iso PU foams.’
First, a reactive, carbonated lignin precursor is created using organic carbonates as a reagent. These carbonates allow ‘molecular zippers’ to be incorporated into the polymer to facilitate breaking it back down into its lignin components at end of life. These can then be used to create new foam.
The lignin is then mixed with a vegetable oil-based curing agent, along with a solvent, a catalyst and a foaming agent. This causes it to bubble up. It is then baked in an oven for about 12 hours at 65°C, to give a foam disc.
Several companies have already expressed an interest in the technology, and the team is now working on potential applications.