Two combined plastics lead to strong adhesion

Patrick Hayes

University researchers made a discovery Thursday that could revolutionize the plastic industry, leading to better diapers and stronger automobile bumpers.
The researchers, led by chemical engineering and materials science professor Frank Bates, have successfully welded together the two highest-volume plastics in the world — polyethylene and polypropylene — to form a single translucent plastic stronger than most others.
“It has the potential to be very important,” Bates said. The plastics industry amounts to more than $100 billion in sales annually.
For manufacturers to use the two plastics before, glue had to hold them together, Bates said. The discovery makes it possible to use a single blend of the plastics that has a stronger adhesion and is less brittle.
For example, automobile bumpers have primarily been made of polypropylene, which becomes brittle when cooled. During crashes in cold weather, bumpers usually crack.
With the new blend, bumpers would withstand the impact in colder conditions.
The discovery will also help build better diapers. Typically, diapers are made of many different layers of glued together plastics. With this new technology, the plastic layers can be spot welded. This eliminates the need for glue, which reduces costs and provides for better adhesion.
It could also help improve the quality of plastic packaging and child car seats.
The discovery is the result of a two-year research project, sponsored in part by an annual $70,000 grant from Exxon Corp., Bates said. The blend is already in use by the corporation.
“(The discovery) represents a very fruitful collaboration between a company and the University,” Bates said.