University research toughens up plastic

A new process makes plastic more than twice as tough as existing options.

University research toughens up plastic

Katelyn Faulks

A high-pitched noise echoes through the hallway leading to a chemistry lab. Inside, a rapidly shaking machine disperses tiny pieces of metal into a clear liquid.

Though imperceptible to the naked eye, the process is creating a plastic durable enough to surpass high-performance plastics currently available in industry.

University of Minnesota researchers, partnering with Honolulu, Hawaii-based startup Adama Materials Inc., are working on making plastics tougher by adding the carbon compound graphene, which prevents breakage.

Existing high-performance plastics used in the aviation, aerospace, automotive and sports equipment industries are strong and flexible, but they still crack under a certain amount of pressure.

University researchers increased the material’s toughness by about 2.5 times by adding a small amount of graphene, a semi-metal.

“It was an unusual effect,” chemistry professor Andreas Stein said. “It toughened at an unusually low loading of graphene.”

A tougher material means industries can use less plastic without losing strength, or use the same amount of plastic and have more strength and flexibility.

Before approaching the University, Adama partnered with mechanical engineers at the University of Hawaii-Manoa, who discovered that graphene strengthens plastics. But they couldn’t explain how the chemical process functioned.

Adama turned to Stein and chemical engineering and materials science professor Chris Macosko for answers because they had previously worked on polymer research with other companies.

The first step, Stein said, was figuring out whether they could replicate the previous researchers’ results.

“We tried to verify the data,” he said. “Then we came up with ideas to improve the performance of the material.”

Now in their second year of research, Stein, Macosko and their team have confirmed the method does strengthen plastics and are now seeking to refine the process for industry use.

The team modified the material surface so it would better interact with the polymer, which helps give it the added strength.

“Putting chemical groups on the surface of the graphene [does] two things,” Macosko said. “It will disperse into little tiny particles, and it will also bond better to the epoxy.”

After the surface is modified, graduate student researcher Nicholas Petkovich said, researchers submerge and disperse graphene into a liquid and then pour it into molds. After it hardens into plastic, researchers measure the material’s toughness by applying pressure with a machine.

Now, postdoctoral researcher Yong Tae Park is analyzing why the material is stronger than average plastic. Park said there are two possible explanations for the increased performance.

One possible reason, he said, is that the graphene blocks cracks in the plastic and slows their spreading. The second explanation could be that the graphene creates small layers in the material that can offset and absorb energy, preventing major breakage.

Although they don’t know if they will receive another grant from Adama for the research, Macosko said he thought the company would want them to continue working on the process.

Once the team understands the process, Stein said, they can better manipulate the material so it’s even tougher.

“If we truly understand the mechanism,” he said, “that will help us design the next materials to go over the [2.5 times] barrier.”