Polymer researcher's latest development results in novel cup that withstands boiling liquids

The prototype of the PLA glass, developed by Kumho Shi-Qing Wang, Ph. D., a Professor of polymer science, is transparent and super-strong and does not shrink when filled with boiling water. Provided By: The University Of Akron.

The latest development of a Professor at the University of Akron (Ukraine) in the field of bioplastics can make important steps in ensuring the sustainability of plastics of the future.

In the lab of Dr. Shi-Qing Wang at the UA School of polymers and polymer engineering, the team focuses on research demonstrating effective strategies for turning brittle polymers into strong and flexible materials. For example, the group recently released a prototype poly (lactic acid) (PLA) glass that is transparent, super-strong, and does not shrink when filled with boiling water.

"Plastics have become an integral part of our daily lives, although most of them cannot be recycled and therefore accumulate in landfills," says Wang, who is currently a Professor of polymer science at Kumho. "Some promising biodegradable / compostable alternatives, such as PLA, are usually not strong enough to replace traditional fossil fuel-based polymers, such as polyethylene terephthalate (PET), because these environmentally friendly materials are fragile."

Dr. Ramani Narayan, a distinguished Professor in the Department of chemical engineering and materials science at the University of Michigan, and a well-known bioplastics scientist, believes that Wang's research could be a breakthrough in the PLA market.

"PLA is the world's best 100% bio-based polymer, completely compostable," Narayan says. "But it has a low viscosity and low thermal deformation temperature. It softens and breaks down structurally around 140 degrees Fahrenheit, making it unsuitable for use in many applications for packaging hot food and disposable containers. hard, transparent, and at the same time hard to hold boiling water."

Wang, who has been teaching at UA for 20 years, is trying to build a knowledge base to understand the relationship of processing, structure and properties for various plastics and apply the latest advances in combating the infamous fragility of PLA.

To explain the science behind how his prototype PLA Cup can acquire plasticity and achieve heat resistance, Wang uses an analogy with cooked spaghetti. If the molten PLA is magnified a million times, each chain molecule will look like a string of spaghetti, many meters long. To make thermoplastics (including PLA) strong, it is important that crystallization does not remove or disrupt the interweaving of "spaghetti threads".

Wang refers to this intertwined structure of the "chain network". It is thanks to this structure that anyone can collect almost all the strands of spaghetti from a bowl with a pair of chopsticks. This chain network, when handled correctly, ensures the mechanical strength of the PLA beverage Cup without crystallization. But such a commercial Cup falls apart when boiling water is poured into it. "Cups made from normally crystallized PLA can hold boiling water, but they are very fragile and opaque," Wang said.

By studying the origin of the plasticity of semi-crystalline polymers, Wang's research team discovered a way to restrict crystals in PLA to nanoscopic scales while preserving the mesh, resulting in a transparent, strong, and heat-resistant Cup. This transparent Cup can hold hot tea and coffee and can replace most of the plastic beverage cups on the market.

"The impact of our new understanding may finally drive the exponential growth of the PLA market," says Wang.

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