Adding seasoning to food often vastly improves the result. And now, a team of researchers from Korea and the Nordic countries has shown that what goes for dinner, apparently also goes for biobased, biodegradable plastics.
A study published in the ACS journal Sustainable Chemistry & Engineering under the title Toward Sustaining Bioplastics: Add a Pinch of Seasoning reports that adding seasoning to the recipe for biobased, biodegradable plastics can boost the strength of the polymer to a measurable degree.
Biodegradable polymers, by their very nature, tend to lack strength, as they are built to disintegrate. As the researchers pointed out, the more easily these materials break down, the flimsier they are, tearing apart from the slightest pressure. “The thermomechanical performance requirements of consumer products are required to match the nondegradable plastics; consequently, the development of commercially available biodegradable products has reached its current nonevolving state,” they wrote.
While additives could provide a solution, traditional petroleum-based products slow down degradation and can be off-putting for consumers who prefer natural, biologically sourced ingredients.
The scientists theorised that what works for food might well also work for biodegradable plastics. They experimented with the use of seasonings such as citric acid and cream of tartar - the latter being a well-known solution for creating thick, stable egg whites and whipped cream, for example.
Jeyoung Park, Dongyeop Oh, Hyeonyeol Jeon, Jun Mo Koo and their colleagues then seasoned a biodegradable bioplastic called poly(butylene succinate) (PBS) with fruit-derived tartaric acid or citric acid to discover whether adding either of these could improve the plastic’s mechanical properties.
Their findings bore out their theory. As they wrote: “The developed “seasoning” brings the properties of PBS, one of the most underwhelming biodegradable and biorenewable polymers, to a new level.”
The researchers created seasoned PBS by first heating succinic acid and 1,4-butanediol with small amounts of either tartaric or citric acid. Then, they added titanium(IV) butoxide and dried the products. In tests, the two new films stretched more than twice as far before breaking and let through less oxygen compared to pure PBS.
Compared to ‘unseasoned’ PBS, the new materials could be successfully used for bags or food packaging, say the researchers. Both materials were stronger than many conventional biodegradable plastics and some petroleum-based products.
One potential downside is that it took the new additive-containing polymers slightly longer to break down in water compared to pure PBS over 14 weeks, though that could be beneficial for food packaging applications in humid environments.
The approach using ‘seasoning’ is relatively simple and straightforward and will enable traditional PBS to be transformed into a biodegradable plastic that ‘overcomes the current limitations and transcends the boundaries of nondegradable products, such as active food packaging and fishing nets, while strategically minimising changes to existing production facilities and processes’.
‘The developed seasoning method and performance outcomes are expected to reposition these biodegradable polymers among replaceable petroleum-based polymers, thereby contributing to a successful petroleum-to-biomass transition,’ they wrote.
Toward Sustaining Bioplastics: Add a Pinch of Seasoning; Hyeri Kim, Giyoung Shin, Min Jang, Fritjof Nilsson, Minna Hakkarainen, Hyo Jung Kim, Sung Yeon Hwang, Junhyeok Lee, Sung Bae Park, Jeyoung Park, Dongyeop X. Oh, Hyeonyeol Jeon, and Jun Mo Koo; ACS Sustainable Chemistry & Engineering 2023 11 (5), 1846-1856; DOI: 10.1021/acssuschemeng.2c06247