WID Scientists Inject More Life into Recyclable Plastics

In an ideal world, all plastics would be engineered with sustainability in mind — at least that’s the research philosophy of WID scientist Srikanth Pilla.

He and Lih-Sheng ‘Tom’ Turng at the WID BIONATES research area are working to find new ways to engineer plastics and extend the life of heavily used products such as beverage bottles and plastic shipping materials.

Looking to enhance the recycling process, the UW System Solid Waste Research Program awarded Pilla and Turng $30,000 to engineer alternative plastics with longer recycling lifespans. Recent data show Wisconsin recycling more than 35,000 tons of plastic every year, according to the state Department of Natural Resources.

Petroleum-based plastics — think of a water bottle, for example — begin to break down after as few as two to three recycling cycles. The same high-heat recycling process that injects new life into plastics also ends up shortening the number of times the products can be recycled. Once the integrity of plastics becomes compromised, the products often need to be discarded in landfills, where they take hundreds of years to break down naturally. But the research aims to find a way to renew qualities lost during the recycling process as well.

“The key is to not only extend the life of plastics, but we’re looking to use a liquid, during reprocessing, to restore the properties that would have been lost otherwise,” Pilla explains.

Researchers combine liquid-like gases called “supercritical fluids,” such as nitrogen gas or carbon dioxide, with polymers and special additives to create and modify plastics. These different formulations combined with unique gas-assisted or foaming technology usually dictate the strength and recycling lifespan of plastics. Pilla says the group’s version of this “fluid” allows plastics to be melted at lower temperatures during recycling, which helps recycled plastics maintain their sturdiness and ability to be processed multiple times. The group believes the technique could boost the life of plastics from two or three recycling cycles to five to seven instead.

Drawing on the work of Turng, who’s also a faculty member at the UW Department of Mechanical Engineering, the research relies on integrating the supercritical fluid through injection molding techniques, which mass produce plastic parts in a sustainable fashion that saves materials and energy.

The group will continue to work on the technique and present its results to the Solid Waste Research Program before fall 2013. Pilla says future research will also look at ways to combine recycled plastics with bioplastics to make an array of environmentally friendly materials with lower carbon footprints.

News related to Turng’s work to create more functional plastics

— Marianne English