Swedish university claims bioplastic breakthrough using indole

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Photo by Theo Hagman-Rogowski The research is led by chemical engineering doctoral student Ping Wang

Scientists at Lund University, Sweden, have produced a bioplastic material based on indole, a heavy organic compound present in human faeces and, in lower concentrations, in certain flowering plants.

Indole, which can smell as strongly as human faeces depending on the amount and combination, was used to replace the hydrocarbon furan in polyethylene furanoate (PEF) bioplastics.

Led by chemical engineering doctoral student Ping Wang, the research produced a plastic which was found to be more durable than both regular plastic and other bioplastics in lab experiments. The material is also potentially better suited for recycling.

The research team is thought to be the only one researching indole-based polyesters, and their results are “promising”, the University of Lund said 15 Jan.

PET, also a polyester, has a glass transition temperature - the temperature at which the material softens and deforms - of 70 degrees Celsius (oC). The most successful experiments with PEF have shown that that material can withstand about 86 oC. However, Ping Wang’s indole plastic is stable up to 99 oC.

“These are preliminary results, but we have seen that [the new] polyester plastic has better mechanical properties, which makes it more sustainable. This can lead to better recycling in the future,” said associate professor Baozhong Zhang, who is supervising the research team. 

Currently, indole is only produced on a small scale and used mainly in perfumes and drugs.  But according to the Lund University team, it may be possible to use bioengineering methods to produce indole from sugar through fermentation. The theory, however, needs further analysis.

Ping Wang is currently working on the indole plastic’s potential in other application areas.

“We obtained good results but are not satisfied. Now we are trying to find methods for making higher quality indole polymers that can be used in more ways, not just for plastic bottles”, she concluded.

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