Biomass-based polymer can be recycled again and again

Polymers - not just plastics, but fibres, films, emulsions and many other forms - are used in every part of life. While they are extremely useful due to their cheapness and versatility, many goods made from polymers are only used once or for a short period before being disposed of. The chemical compounds released by some polymers make them a serious environmental threat.

Although some polymers can be recycled, such as PET, few can be recycled many times; the goods made from secondary raw materials tend to be lower in quality compared with goods made entirely from primary raw materials.

Most modern plastics are derived from petrochemicals like petroleum or natural gas, which undergo polymerisation to form polymers. However, the polymers developed by the St Petersburg State University team are based on biomass compounds. The key component of these polymers is terpenols; these are compounds from natural alcohols, such as menthol (a compound derived from mint oil) and borneol (a compound derived from oil from the white fir tree).

The polymers synthesised from these biomass compounds may be used for both primary and secondary recycling. During secondary recycling, the product may be converted into the primary compounds and followed by polymerisation. These polymers can be recycled at moderate temperatures of around 120°C, reshaped, and cooled to form a different product.

“This can be said about recycling the materials based on our polymers,” said first author Svetlana Metlyaeva, a research at the university’s Laboratory of Cluster Catalysis. “If they are recycled without oxygen, we can get natural alcohols or their derivatives that can be restored to the same alcohols. Because they are widely found in nature, they do not harm the environment.”

The researchers repeated the cycle seven times, and concluded that the polymers – despite repeated recycling – did not appear to change their properties.

They plan to continue their work on the biomass-based polymers, studying the mechanical properties of the polymers, such as resilience, elasticity, and strength. This is an important step in the road towards introducing them in industry.

“What we have achieved so far is only the ability to synthesise these polymers. Yet the properties of the polymer-based materials can vary. This depends on the way in which we synthesise them and what compounds we use. Now we have to modify the polymers themselves and the materials based on them. Then, we will be able to talk about how we can use them.”