Japan scientists create plastic that dissolves in seawater within hours

Japanese researchers have unveiled a new plastic that fully dissolves in seawater within hours, offering a promising solution to the escalating crisis of ocean pollution and microplastics.

A research team in Japan has developed a breakthrough plastic that disintegrates in seawater in as little as two to three hours, potentially revolutionizing the fight against marine pollution. The innovation, co-developed by the University of Tokyo and Japan’s premier research institute RIKEN, retains the strength of conventional petroleum-based plastics but vanishes in saltwater without leaving harmful residues.

The plastic is made by bonding two ionic monomers to form a salt-based structure that remains strong in normal use but breaks down in saline conditions. Once exposed to seawater, the material dissolves into its original monomers - compounds that can be further digested by naturally occurring bacteria.

“When we place it in an aqueous solution with the same salt concentration as seawater, it dissolves quickly in about two to three hours, depending on its thickness and size,” said lead researcher Takuzo Aida, Group Director at RIKEN’s Center for Emergent Matter Science (CEMS). “Essentially, it returns to its monomer components.”

In a demonstration at RIKEN's Wako City lab near Tokyo, a small sheet of the plastic visibly disappeared in saltwater after light agitation, underscoring the material’s potential.

Aida emphasized that many so-called biodegradable plastics do not fully decompose and instead contribute to harmful microplastic pollution. In contrast, their newly developed plastic avoids that outcome.

The development comes amid dire warnings from the UN Environment Programme, which predicts plastic pollution will triple by 2040, with 23–37 million metric tons entering oceans annually. In 2020 alone, an estimated 2.7 million metric tons of microplastics - tiny fragments under 5mm - entered the environment, harming both marine ecosystems and human health.

Microplastics have been detected in the human brain, arteries, and various organs, sparking global concern over their long-term impact.

While commercialization plans have yet to be finalized, Aida said there is growing interest, particularly from Japan’s packaging industry, which relies heavily on plastics. "If we can really manage to reduce that, we can expect less environmental damage,” he noted.

Currently, only about 9% of the world’s plastic waste is recycled, highlighting the urgent need for sustainable alternatives.

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