Research carried out by a team in Dublin has found that technologies used in plastics manufacturing can jeopardise food safety and the environment.
AMBER Centre researchers based at Trinity College Dublin (TCD) have discovered that the way many everyday plastics are manufactured builds unseen stress into the material, stress that later drives the release of tiny plastic particles into food and the environment.
When factories mould plastics into water pipes, bottles, and household products for food preparation, they cool the molten plastic quickly, so it keeps its shape, according to the team of researchers.
They explained that as it cools, the plastic naturally shrinks, causing a pressure build-up that ultimately gets frozen-in as an internal pressure or stress.
The new study shows that this ‘frozen-in’ stress causes plastic surfaces to erupt into microscopic blisters. When these blisters burst open, they shed minute fragments – micropollutants – into the surrounding environment.
Plastics in food?
Polyethylene and polypropylene – the two most widely used plastics – account for about 71 % of all plastic pollution found in the environment, according to the AMBER team.
By tracing how stress arises during manufacturing, the team uncovered a previously overlooked source of pollutants released from these plastics.
In laboratory tests the scientists deformed flat sheets of polyethylene and polypropylene, mimicking the stress frozen into real products.
Nanoscale blisters formed and grew in number and size as the stress level increased, forcing polymer and chemical additives from inside the plastic sheet onto its surface, from where they were released as micropollutants into the environment.
The same type of blisters formed inside commercial polypropylene bottles, especially around the highly stressed neck and cap regions, generating the vast majority of the plastic pollutants detected in the contents of these bottles.
The research team said that the discovery shows that frozen-in stress is a critical vulnerability that catalyses plastic degradation and the release of micropollutants.
Low-cost, high-speed manufacturing methods are major contributors to the levels of stress found in plastic products today, according to the research.
Global plastic production reportedly now exceeds 400 million tonnes annually, of which 20 million tonnes leaks into the environment.
Scientists now estimate that 170 trillion plastic particles are floating in the oceans. Micro and nanoscale plastics have been detected throughout the human body, with significant accumulations in the brain, heart and lungs, the team of researchers stated.
Lead researcher, professor at the School of Chemistry at Trinity College Dublin, Prof. John Boland said: “From the standpoint of current manufacturing practices, plastics are naturally prone to falling apart.
“To protect food, water and the wider environment, manufacturers urgently need to develop smart processing technologies that minimise the levels of built-in stress in plastic products.”
The full findings are published in Nature Communications under the title ‘Stress‑induced phase separation in plastics drives the release of amorphous polymer micropollutants into water’.
AMBER
AMBER is the Research Ireland (formerly Science Foundation Ireland) Centre for Advanced Materials and BioEngineering Research.
The centre brings a multidisciplinary partnership between leading academics in advanced materials science, bioengineering and industry.
Working collaboratively, it develops new materials and devices for the ICT, medical devices, energy, and sustainable industrial technology sectors.
