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New PS adhesive discovered: Benign and cheap?

July 14, 2010

A wood scientist at Oregon State University makes the incidental discovery of a pressure sensitive adhesive made from vegetable oils, not petrochemicals.

The industry might have a new pressure sensitive adhesive to work with in the near future. If all goes according to plan, the glue will be environmentally benign, easy to produce, and cheap to acquire. It's made from vegetable oils, and uses no petrochemicals or toxic substances in the formula or in the process of manufacture.

Kaichang Li at work in his lab.
The discovery of the new glue was incidental. In a wood products laboratory at Oregon State University in Corvallis, OR, USA, Kaichang Li was trying to produce a hot-melt adhesive that could be used in a wood-based composite product – an application that would require the adhesive to be solid at room temperature and melt at higher temperatures. He failed.

"We were working toward a hot-melt composite adhesive that was based on inexpensive and environmentally friendly vegetable oils," says Li, a professor of wood science and engineering in the OSU College of Forestry. "But what we were coming up with was no good for that purpose. It wouldn't work."

Not all was lost, however. "I noticed that at one stage of our process the compound was a very sticky resin," he adds. "I told my postdoctoral research associate, Anlong Li, to stop right there. We put some on a piece of paper, pressed it together and it stuck very well, a strong adhesive."

The next step in the scientists' work was to explore the qualities of the new adhesive. "A company nearby provided us with some equipment, and we performed various tests," Li says. These included tests for peel and sheer properties. "It behaves like a typical adhesive made from petrochemicals. It's really good stuff. I like it."

Li declares that the adhesive "is incredibly simple to make, doesn't use any organic solvents or toxic chemicals, and is based on vegetable oils – renewable crops such as soy beans, corn or canola oil – that would be completely renewable, not petrochemicals. It should be about half the cost of existing technologies and appears to work just as well."

There have been previous attempts to make pressure-sensitive adhesives from vegetable oils, Li notes, "but they used the same type of polymerization chemistry as the acrylate-based petrochemicals now used to make tape. They didn't cost much less or perform as well. The new approach used at OSU is based on a different type of polymerization process, and produces pressure-sensitive adhesives that could be adapted for a wide range of uses, perform well, and cost much less."

The technology should be fairly easy to scale-up and commercialize, Li says.

"OSU has applied for a patent on this technology, and we're looking right now for the appropriate development and commercialization partner," says Denis Sather, a licensing associate with the OSU Office of Technology Transfer. "We believe this innovation has the potential to replace current pressure sensitive adhesives with a more environmentally friendly formulation at a competitive price."

Li hinted that the university might be close to making an agreement with a partner to further develop and commercialize the adhesive.

An expert in wood chemistry, composites and adhesives, Li has already changed the face of the wood composites industry. His research created a formaldehyde-free adhesive that can be used in the production of plywood and particle board that is non-toxic, and is now becoming more widely used in that industry. That invention was inspired when he watched mussels clinging tenaciously to rocks despite being pounded by ocean waves, and he later duplicated in a laboratory the type of compound they use as an adhesive to accomplish that.

For these advances, in 2007 Li received the Presidential Green Chemistry Challenge Award from the Environmental Protection Agency. It recognized his continued work to reduce toxic chemicals used in manufacturing processes.

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