Team Analyzes Nature-Based Adhesive Alternative
Chemists from Purdue University have reportedly developed a sustainable adhesive system that draws inspiration from the natural world.
Led by professor of chemistry in the College of Science and of materials engineering Jonathan Wilker, the team’s findings were recently published in the journal Nature.
About the Research
According to the university’s press release, Wilker and his team have studied “sticky substances” for years, analyzing marine animals that adhere to try and create more sustainable adhesives that work as well as any glue.
“Our current adhesives create all sorts of environmental problems,” Wilker said. “Almost all glues are petroleum-based and do not degrade. The bonded materials in our products stay stuck together.
“Consequently, we cannot recycle many of the materials that we put into our recycling bins. Discarded products will sit in landfills for centuries and, sometimes, contribute to ocean microplastics.”
For example, newly built houses utilize formaldehyde in their plywood building material, potentially exposing residents to carcinogens. However, these traditional building materials are already strong, easy to produce and relatively inexpensive, Purdue says.
“By studying how nature makes adhesives, we are learning how to design new technologies for our future society,” Wilker said. “Given all of the problems generated by current glues, we feel an obligation to create something better. Ideally, new adhesives will be bio-based and nontoxic. Strengths should be as high as current products.
“Then we would like to bond them strongly when needed and also be able to take the substrates apart when wanted. Further design constraints that we grapple with, in order to have impact, are costs needing to be low and having all starting compounds available at large scales.”
After a series of experiments, the team settled on utilizing an epoxidized soy oil for a main component, which is already produced globally on a “massive” scale. For their work, the smallest container that they could reportedly purchase was a 55-gallon drum and, since each experiment used just a of the oil, the level in their drum has dropped only a few inches after several years of testing, Purdue explains.
Wilker and his team then added the epoxidized soy oil to malic acid, a compound most known for giving apples their tart flavor, and tannic acid, which is found in trees, red wine and black tea. Those three ingredients added up to an adhesive that is “inexpensive, effective, scalable, practical to produce and completely sustainable.”
According to the university, for the research, the scientist bonded together objects and then used an instrument for breaking the bonds and measuring forces. The team tested wood, plastics or metals.
The new adhesives reportedly held up well in many cases, sometimes performing similarly to or better than, traditional adhesives such as a superglue and an epoxy.
“If you combine these components under the right conditions, adhesives can be made that are as strong as epoxies,” Wilker said. Epoxies are generally considered to be the highest performance class of adhesives.
“All of the components are bio-based, safe and already available at train car scales. A bonus is that the adhesive is easy to make. Basically, you can mix and heat the components.”
Further research will refine the system and work to maximize its impacts in areas ranging from medical innovations to industrial materials to packaging. Other bio-based compounds can also reportedly be used with epoxidized soy oil, generating an entire family of new sustainable adhesives.
Wilker reportedly disclosed his adhesives to the Purdue Innovates Office of Technology Commercialization, which has applied for a patent. The research was supported by the Office of Naval Research.