Polymer Researcher’s Latest Development Results in New Cup That Resists Boiling Liquids

The latest development by an Akron University (UA) professor in the field of bioplastics has the potential to make significant strides in the sustainability of future plastics.

In the lab of Dr Shi-Qing Wang of the AU School of Polymer Science and Polymer Engineering, the team is focused on research that presents effective strategies for turning brittle polymers into hard, flexible materials. For example, the group recently produced a prototype poly (lactic acid) (PLA) cup that is transparent, super strong and does not shrink when filled with boiling water.

“Plastics have become an essential part of our daily life, although most cannot be recycled and therefore accumulate in landfills,” says Wang, who is currently professor of polymer science at Kumho. “Some promising biodegradable / compostable alternatives, such as PLA, are generally not strong enough to replace traditional fossil fuel-based polymers like poly (ethylene terephthalate) (PET) because these durable materials are fragile.”

Dr Ramani Narayan, a distinguished professor in the Department of Chemical Engineering and Materials Science at Michigan State University, and a renowned bioplastics scientist, says Wang’s research has the potential to be a breakthrough in the PLA market.

“PLA is the world’s first 100% bio-based and fully compostable polymer,” says Narayan. “But it has low toughness and a low heat distortion temperature. It softens and structurally collapses around 140 degrees Fahrenheit, rendering it unusable in many hot food packaging and disposable container applications. Dr. Wang’s research could be disruptive technology because his prototype PLA cup is strong, transparent and yet rigid to hold boiling water. “

Wang, who has been teaching at AU for 20 years, has attempted to establish a knowledge base to understand the treatment-structure-property relationship for various plastics and apply the latest knowledge to address the notorious fragility of PLA.

To explain the science behind how his prototype PLA cup can gain ductility and achieve heat resistance, Wang uses the cooked spaghetti analogy. If the molten PLA is amplified a million times, each chain-like molecule would look like a strand of spaghetti several feet long. In order for thermoplastics (including PLA) to be strong, it is important that crystallization does not remove or disrupt the interlacing of “spaghetti strands”.

Wang calls this intertwined structure the “chain network”. It is thanks to such a structure that anyone can scoop up almost any spaghetti strand from a bowl with a pair of chopsticks. This chain network, when properly handled, ensures that the PLA cup is mechanically strong without crystallization. But such a commercial mug collapses when boiling water is poured into it. “Normally crystallized PLA cups can hold boiling water but are terribly brittle and opaque,” ​​Wang said.

By investigating the origin of ductility in semi-crystalline polymers, Wang’s research group discovered a way to limit crystals to nanoscopic scales in PLA while preserving the lattice, resulting in a transparent, tough cut. and heat resistant. Such a transparent cup can hold hot tea and coffee and could replace most plastic cups on the market.

“The impact of our new understanding could finally drive the exponential growth of the PLA market,” Wang says.