- Widely used polyurethanes don’t degrade and are hard to recycle
- Replacing petroleum with bio-based components could make polyurethanes more sustainable
- Computational models speed the process of selecting bio-materials
At least 20 million mattresses are discarded each year in the US alone, and each one may occupy up to 40 cubic feet in a landfill.
But unlike mattresses of old that were stuffed with natural materials such as straw, wool, or feathers, most modern mattresses are made of polyurethane foam—and very difficult to recycle.
In a presentation made at PRACEdays18 in Ljubljana, Slovenia in May, Fiser explained that polyurethanes are one of the most widespread polymers, used not just in mattresses but in everything from home insulation to the automotive and medical industries.
“If we want to live in a sustainable society, we need to think about how to recycle polyurethanes,” says Fiser. “If we just throw them away, we’re increasing the garbage around us.”
Most polyurethanes are formed by reacting an isocyanate with a petroleum-based polyol. Since oil is a finite resource, substituting a bio-based polyol would make the resulting polyurethane a more sustainable product with greater degradability.
In looking for that substitute polyol, Fisers’ group wanted a material that was both cheap and widely available. Which is why they chose something you’d find in your kitchen cabinet: sugars.
They narrowed it down to five candidates—sucrose, fructose, glucose, maltose, and mannitol—and used computation to select the best one.
The high-performance computing cluster at the University of Miskolc and time on the Hungarian national supercomputer network helped the researchers assess the reactivity both within and between the sugars.
“We used computational chemical models to study the reaction between the isocyanate model we created and between these sugars. Based on the calculations, we were able to compare the reactivity of the different sugars and finally selected fructose as the best candidate,” says Fiser.
They then worked in the lab for several months to come up with the right procedure, experimenting with various blowing agents, catalysts, and temperatures. Graduate student Min-Yen Lu performed most of the synthetic work with the help of department engineer Attila Surányi.
“Even though we speeded the process using computers, we still needed to do hard work in the lab,” Fiser says.
After several months, they were able to synthesize a solely fructose-based polyurethane foam. This was the first attempt to use only fructose in the polyol side.
Says Fiser, “Previous attempts have replaced some of the petro-based polyol with up to thirty percent fructose, but as far as I know, there have been no attempts to replace everything on the polyol side.”
Their fructose-based foam is hard and so won’t be useful for mattresses or seat cushions but could work well for heat insulation. If it turns out to have too much degradability there is still the potential for agricultural applications, such as using the foam to spray seed on a plowed field for rapid planting.
“When you are creating a product through your research, you are not only creating an item which will be good for one thing, but are also looking for other applications,” says Fiser.
Scientific inquiry doesn’t always lead where you might expect, but those diversions can have unexpected rewards. It’s all about discovery and following where the results take you—and that should give anyone sweet dreams.