Her research group is studying adhesives made from by-products of soybean, corn, sorghum and biomass fuels.
"There are two important forces driving this research. We're trying to develop these bio-based adhesives to replace environmentally hazardous materials," Sun said. "Also, we need high-value products to sustain the biofuels economy," she added.
Sun said that the adhesives commonly used in construction products like kitchen floors and laminate furniture are formaldehyde-based and isocyanide-based.
"The isocyanide-based adhesives are toxic," she said.
Moreover, the formaldehyde-based adhesives affect air quality and human health because the compound's carbon and nitrogen bonds are reversible in humid conditions, emitting formaldehyde into the air.
On the other hand, Sun said that biofuels producers need co-products like adhesives to make sustainable fuels economically viable.
For biomass biofuels, the amount of energy that goes into producing them is still greater than the energy that the biofuels can produce.
"Biomass by its nature contains not just sugar necessary for the biofuel, but also lignin, protein and other materials," Sun said.
"So after you convert it into biofuel, you still have a lot of leftovers. So you have to develop high-value chemicals and bio-based products out of that biomass to balance the economics," she added.
"Lignin, a major by-product of cellulosic biomass, is what holds plants upright," Sun said.
Without it, plants would grow flat on the ground.
"This property makes it a good basis for polymers. Lignins show promise for adhesives because they're rich in aromatic structures with many functional groups," said Sun.
Sun also said that plant oils have properties that make them suitable for adhesives that are activated by pressure.
She said that it's also important to design pressure-sensitive adhesives that can be applied quickly to products in the factory.
"If your adhesives are good but it takes a few hours to cure, the industry won't pick it up," Sun said. "So, it's not just a structural challenge, it's also a performance challenge and an economic challenge," she added.
Sun's group also studies proteins with a specific structure that relate to adhesion properties.
"The social impact of our work at the Bio Materials and Technology Laboratory is on environmental quality and biofuel sustainability, which will improve people's life in long term," Sun said.