A polymer that could replace PLA and lead to more degradable plastic bags is being spearheaded by chemists at the University of Florida, USA.

PhD student chemists Ryan Martin and Stephen Miller synthesised polyesteracetal (PEA) using vanillic acid, derived from vanillin, a lignin-based by-product of the paper pulping industry. They claim the material is better suited to modern environmental demands than other disposable plastics. ‘PLA is the current market leading green plastic, but it is essentially a century-old material,’ says Martin. ‘PEAs, however, are 21st century materials and are thoughtfully designed on the molecular scale.’

The main strength of PEA, according to Martin, lies in its superior degradation properties, achieved using strategically placed degradable functional groups along the polymer chain that allow for more facile degradation under landfill or ocean conditions. ‘Previous materials, including PLA, degrade under normal environmental conditions in approximately 500-1000 years. The PEA breaks down in as little as five to ten years. This timescale is really a sweet spot that would allow for a disposable material to mitigate the trash crisis while still serving a useful lifetime.

‘Degradation studies were performed at ambient temperature under a range of pH conditions, as well as in the Atlantic Ocean.

The impact PEAs could have on the US$400 bln/year disposable plastics industry is significant, says Martin. Made from biomass or agricultural waste, PEAs ‘have a green birth, a useful life, and a green death, and have properties that are on par with, or better than, existing materials’. He adds that the material can be produced on a similar cost scale as PLA. Martin continues that as oil becomes increasingly scarce and costly, PEAs could eventually capture the market of petroleum-based plastics such as PE, PP, PS, and PET.

Plastic staying power

Though Martin applauds the intentions behind initiatives to get people to stop using plastic bags, he cannot see them being a success in the long-term. ‘Plastics are popular materials because of their extreme convenience. Getting consumers to stop using plastic bags is counterconvenient, and therefore not likely to be a sustainable long-term solution. The best-case scenario is one in which the materials we have come to love are reinvented to retain their usefulness and convenience, while being produced in an increasingly thoughtful and responsible way.’

Furthermore, he claims that PEA, though made under the same conditions as PLA, has a higher glass transition temperature, (meaning it could replace polystyrene cups, unlike PLA, which deforms) improved optical clarity, and decreased brittleness. ‘We believe this is largely due to increased anomeric interactions associated with the acetal groups, and this will be described in further detail in an upcoming literature publication,’ notes Martin.