Bioplastics are plastics materials made out of biomass instead of crude oil and natural gas. They are more environmentally friendly, but they tend to be less firm and flexible than conventional plastics. They’re also not so stable when subjected to heat.
Fortunately, scientists at the University of Akron (UA) have found a solution to the last shortcoming, pushing the envelope of what bioplastics are capable of. Their development could contribute significantly to the sustainability of future plastics.
Dr. Shi-Qing Wang’s lab at UA focuses on researching effective strategies for converting brittle polymers into rigid and flexible materials. The group’s latest development is a prototype poly(lactic acid) (PLA) cup that is super tough, transparent, and does not shrink or deform when filled with boiling water.
Wang said:
Plastics have become an essential part of our daily lives, though most cannot be recycled and therefore accumulate in landfills. Some promising biodegradable/compostable alternatives, such as PLA, are typically not strong enough to replace traditional fossil-fuel-based polymers like poly(ethylene terephthalate) (PET) because these sustainable materials are brittle.
PLA is a popular form of bioplastic used for packaging and utensils because it’s cheap to produce. Until this advancement at Wang’s lab, the use of PLA was limited because it couldn’t handle high temperatures. That’s why the research could be a breakthrough for the PLA market.
Dr. Ramani Narayan, a renowned scientist in the bioplastics space and a distinguished professor at Michigan State University, said:
PLA is the world’s foremost 100% biobased and fully compostable polymer. But it has low toughness and a low heat distortion temperature. It softens and structurally collapses around 140 degrees Fahrenheit, making it unusable in many hot food packing applications and disposable containers. Dr. Wang’s research could be disruptive technology because his prototype PLA cup is tough, transparent, and yet rigid to hold boiling water.
The team reimagined PLA plastics’ intricate structure on a molecular level to achieve heat resistance and gain ductility. The material is made up of chain-like molecules bundled together like a bunch of intertwining spaghetti strands. To be a tough thermoplastic, the researchers had to ensure that crystallization didn’t disrupt the interwoven structure. He explains it as being able to pick up all the noodles at once with a pair of chopsticks vs. just a few strands slipping away from the rest.
Their prototype PLA plastic cup could hold boiling water without degrading, shrinking, or turning opaque. Such a cup could be used as a more environmentally friendly alternative for coffee or tea.
