In Sweden, a new, fossil-free bioplastic is emerging that is more durable than both regular plastic and other bioplastics, and is potentially better suited for recycling – and it is based on indole, a heavier hydrocarbon molecule than furan, that is present in human feces and smells accordingly.
The research team is thought to be the only one researching indole polyesters, and their results are promising. A regular PET bottle’s glass-liquid transition temperature – when the material softens and deforms – is 70 degrees. However, chemical engineering doctoral student Ping Wang’s indole plastics is stable up to 99 degrees.
“These are preliminary results, but we have seen that polyester plastic has better mechanical properties, which makes it more sustainable. This can lead to better recycling in the future. At present, PET bottles can only be recycled once, then they must be used for something else such as textiles”, says 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. It may be possible to use bioengineering methods to produce indole from sugar through fermentation. However, such a process would first need to be analysed more thoroughly before the production cost can be calculated.
“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”, said Wang.