No More Microplastics: Plant-Based Plastic Decomposes in the Sea
Researchers have found a way to reduce microplastics in the oceans. They developed a plastic that biologically decomposes in saltwater.
A plastic bag decomposes under the influence of saltwater.
(Image: RIKEN english channel/Screenshot)
A team of scientists at Japan's RIKEN Center for Emergent Matter Science (CEMS) has developed a plastic based on plant cellulose that decomposes in salty seawater without leaving behind microplastics. If applied globally, this could be an option to reduce the heavily increasing marine pollution caused by microplastics.
Microplastics are dangerous to humans and the environment. They are found in soil, the sea, and in animals and plants. Humans can also ingest the small plastic particles, often around one micrometer in size. They can lodge in tissues and enter the bloodstream, depositing in the heart, respiratory tract, and kidneys. This can have harmful effects. The risk of heart attack, stroke, and diabetes up to death increases, according to various studies, as the Ă„rzteblatt writes.
The supramolecular plastic developed by the Japanese research team consists of two polymers held together by reversible interactions, write the researchers in the study “Supramolecular Ionic Polymerization: Cellulose-Based Supramolecular Plastics with Broadly Tunable Mechanical Properties,” published in the Journal of the American Chemical Society.
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One of the two polymers is a biodegradable wood cellulose derivative called carboxymethyl cellulose (CMC), which is already commercially available. The researchers had to find the second compatible polymer through several attempts. They found it in a plasticizer made of positively charged polyethyleneimine guanidinium ions. To produce the plastic, they mixed the cellulose and the guanidinium ions in water at room temperature. The negatively and positively charged ions were strongly attracted to each other, forming a solid plastic.
Decomposition in Saltwater
Under the influence of saltwater, the salt bridges break and the plastic decomposes. To prevent unintentional disintegration, the plastic can be coated with a thin protective layer that acts temporarily.
However, the transparent and extremely hard plastic initially had a problem: due to the cellulose content, it was brittle and broke like glass. The scientists used the salt choline chloride – an FDA-approved, biodegradable nutrient – as a plasticizer to prevent this. Depending on the amount added, the plastic can be produced with the desired elasticity. By adding the salt, the researchers achieved an expansion of the plastic by up to 130 percent of its original size. Furthermore, the plastic can be made into a film with a thickness of up to 0.07 mm.
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The scientists say that the biodegradable plastic they developed, which decomposes in saltwater, is just as stable as petroleum-based plastics. Its mechanical properties can be adapted depending on the intended use of the plastic. This does not affect its degradability.
The researchers hope that their plastic will now move from the laboratory to industry worldwide. The researchers have already demonstrated the production of flexible plastic bags from the material, which completely dissolve in seawater and can be recycled in a loop with electrolytes – a possible way to reduce marine pollution.
(olb)
