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Plastic waste on beach

Polymer that degrades under ultraviolet light could solve ocean plastic pollution

Image credit: Dreamstime

A new polymer that degrades under ultraviolet radiation has been developed by Cornell University scientists and could help to deal with plastic pollution.

Commercial fishing contributes to about half of all floating plastic waste that ends up in the oceans. Fishing nets and ropes are primarily made from three kinds of polymers: isotactic polypropylene, high-density polyethylene, and nylon-6,6, none of which readily degrade.

“We have created a new plastic that has the mechanical properties required by commercial fishing gear. If it eventually gets lost in the aquatic environment, this material can degrade on a realistic time scale,” said lead researcher Bryce Lipinski. “This material could reduce persistent plastic accumulation in the environment.

“While research of degradable plastics has received much attention in recent years, obtaining a material with the mechanical strength comparable to commercial plastic remains a difficult challenge.”

The research team has spent the past 15 years developing the plastic called isotactic polypropylene oxide, or iPPO.

While its original discovery was in 1949, the mechanical strength and photodegradation of this material was unknown before this recent work. The high isotacticity (enchainment regularity) and polymer chain length of their material makes it distinct from its historic predecessor and provides its mechanical strength.

Lipinski noted that while iPPO is stable in ordinary use, it eventually breaks down when exposed to UV light. The change in the plastic’s composition is evident in the laboratory, but “visually, it may not appear to have changed much during the process”.

The rate of degradation is light intensity-dependent, but under the team's laboratory conditions the polymer chain lengths degraded to a quarter of their original length after 30 days of exposure. Ultimately, the team hopes to leave no trace of the polymer in the environment.

Last year, another research team demonstrated a process that converts plastic waste into usable jet fuel.

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