A major advancement in structural adhesives for the automotive industry has been developed by researchers at Nagoya University. This next-generation adhesive promises to revolutionize material bonding by offering unprecedented impact strength—22 times higher than traditional epoxy-based adhesives that do not incorporate any rubbery additives.

By connecting car parts with the stronger, more flexible adhesive, cars that use lighter components, such as aluminum and fiber-reinforced plastic, can be produced. The results were published in ACS Applied Materials & Interfaces.

"Structural adhesives with high strength and durability are essential in the assembly of automobiles, aircraft, and buildings," Nagoya University researcher Atsushi Noro explains.

"Epoxy resin-based adhesives are widely used; however, they lack flexibility, making them susceptible to damage under impact. To overcome this, we combined a hydrogen-bonded styrenic thermoplastic elastomer with an adhesive, resulting in a new type that offers both flexibility and outstanding impact resistance."

The new adhesive was created in collaboration with Aisin Chemical Company. Their innovative adhesive suggests a new use for hydrogen-bonded styrenic thermoplastic elastomers, a previous creation of Nagoya University.

A hydrogen-bonded styrenic thermoplastic elastomer is a polymer that exhibits rubbery properties, allowing it to stretch and return to its original shape. These properties enabled the creation of a more robust adhesive with improved stress dissipation during impact.

In addition, the hydrogen bonds formed within the elastomer in the adhesive allow it to separate and reconnect in an instant under stress, further increasing its toughness.

This breakthrough has important implications for the automotive industry, as it addresses the need for stronger, more flexible adhesives capable of bonding dissimilar materials in lightweight, multi-material vehicle designs.

"Structural adhesives are expected to play a key role in reducing vehicle weight, which is critical for improving fuel efficiency and lowering emissions," Noro said. "The adhesive's ability to bond various materials, such as metals and fiber-reinforced plastics, enables the design of lighter vehicles without compromising safety or performance. This development is a significant step forward in the pursuit of a carbon-neutral society."

Although it is expected to be an invaluable tool in the automotive industry's quest for sustainability and performance, the researchers expect that, as research continues, it can be used in other industries, such as aerospace and construction, reducing the weight of materials used and improving the carbon cost in these heavy industries.