Illustration by Joy Smoker

Whether you’re wrapping a gift or bandaging a wound, you rely on an adhesive to get the job done.

These sticky substances often are made from petroleum-derived materials, but what if there was a more sustainable way to make them? Now, a team of engineers at the University of Delaware has developed a novel process to make tape out of a major component of trees and plants called lignin—a substance that paper manufacturers typically throw away. What’s more, their invention performs just as well as at least two commercially available products.

The researchers recently described their results in ACS Central Science, and they are working on more ways to upcycle scrap wood and plants into “designer materials” for consumer use.

Sticky science

Lignin is a renewable resource, a substance in trees that helps to make them strong. But you do not have to cut down trees to get it, because there’s plenty lying around. When pulp and paper manufacturers process wood, the lignin is left behind and usually discarded in landfills or burned for heat. Some companies are even willing to deliver a free dump truck full of the stuff because that is cheaper than disposing of it in a landfill. An inexpensive, plentiful and sustainable material, lignin presents a prime opportunity for some scientifically advanced upcycling.

Lignin is also a natural polymer, a material made of very large molecules composed of smaller subunits called monomers. Lignin shares some structural and materials property similarities with petroleum-derived polymers, such as polystyrene and polymethyl methacrylate, which are commonly used in adhesives and other consumer products, from packaging materials to cups.

“One of the thoughts that we have always had is: Can we take lignin and make useful products, and in this case, useful polymers out of it?” said Thomas H. Epps, III, the Thomas and Kipp Gutshall Professor of Chemical and Biomolecular Engineering, Professor of Materials Science and Engineering at UD, and the corresponding author of the new paper. In particular, Epps suspected that lignin could be used to make adhesives with similar strength, toughness, and scratch resistance to the petroleum-based versions.