Engineers transform waste wood into adhesive tape
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Researchers at the University of Delaware have developed a technique for transforming discarded wood scraps into adhesive tape which performs as well as commercially available tapes.
Like plastic bags, cups and packaging, adhesive tapes are normally made from petroleum-derived materials. For instance, Sellotape is made from polypropene and duct tape is coated with polyethylene.
As governments, businesses and individuals work to cut down and replace plastics – such as by introducing plastic bag bans – a team of University of Delaware engineers have been working on a sustainable alternative to petroleum-derived plastic tapes.
The engineers have developed a process for making adhesive tape using lignin: a substance found in plants which is vital for giving plant cells their rigidity. Lignin is a waste product left over from paper manufacturers, and is thrown away or burned in huge volumes. It was of interest to the Delaware researchers as it is a renewable resource and a natural polymer which shares some material properties with the petroleum-derived polymers used to make adhesive tape.
“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 Professor Thomas Epps, a materials engineer at the University of Delaware and lead author of the study.
In order to turn tough lignin into a useable polymer, the researchers began by breaking down scraps of poplar wood through a low-temperature depolymerisation process that reduces the lignin into molecular fragments. Once broken down, the lignin can be used to create new adhesive materials.
“We can use the same separation, purification, polymerisation and characterisation methods to make these materials as one can use to make the current commercial and petroleum-based analogues,” said Epps. “But we can get better properties and we can use a much greener source.”
The researchers were pleased to find that their sustainable adhesive tape performs just as well as Scotch Magic Tape and Fisherbrand labelling tape, demonstrating good strength, toughness and scratch resistance, even without the addition of materials such as “tackifiers”, which are commonly used to increase adhesion.
In future, the Delaware engineers hope to explore the use of lignin from other plants, such as switchgrass, in the manufacture of adhesive tape. According to the researchers, there is the potential to use different lignins to create adhesives for different purposes, and even other plastic-based objects such as rubber bands.
“If I need something that is a little bit tacky, I might use a slightly different tree for that,” said Epps. “If I want something that is less tacky and leaves less residue, I might use a different tree. There is a lot of opportunity to use biodiversity to fine-tune the end product.”