350 million metric tons of plastic are produced globally every year.  To put this into perspective, here’s a brief list of things that weigh ONE ton: a walrus, the Liberty Bell, a baby humpback whale, a giraffe, a great white shark, etc.

Now imagine you have a herd of 79,000 walruses.

Combined, these two walruses equate 0.0025% of the total weight of plastic in the Great Pacific Garbage Patch.  Picture courtesy of Creative Commons.

That is the low estimate of how much plastic has accumulated in the Great Pacific Garbage Patch (GPCP), 1.6 million square kilometers between California and Hawaii.  And this is only one part of the ocean!  As of 2015, plastic fishing gear such as nets, ropes, and lines, encompasses 52% of the GPCP’s mass.  On top of this, waste fishing materials are also the primary cause of “ghost fishing,” the unintended trapping of marine wildlife.

“… estimated 4 to 12 million metric tons of plastic lost annually to marine environments.”

In order to combat this calamity, a team of chemists funded by the National Science Foundation published their work in early 2020 depicting a polymer that breaks down over time.  The polymer, isotactic polypropylene oxide or iPPO has been shown to degrade when exposed to ultraviolet (UV) radiation, the same type of radiation emitted from the sun.  Over a span of 30 days of constant UV exposure, iPPO’s chain lengths reduced to a quarter of their original size; this means the material will react with its surroundings and thus break down faster than the standard polymers used in fishing equipment.

The ability of iPPO to break down relatively quickly is huge, but in order for it to replace traditional plastics in the fishing industry, it must also be physically sturdy.  Fortunately, with a few small tweaks referred to as “robust string hardening,” iPPO’s strength is able to match that of the most popular plastic used in fishing: nylon-6,6.  With this in mind, the research team is hopeful that iPPO will replace nylon-6,6 in the near future.

Fishing boats. Picture courtesy of Creative Commons.

Of course, this isn’t the end of their research.  A plastic that is able to break down faster than others is a huge step forward, but it’s not the end-all-be-all.  The team’s ultimate goal is to leave no trace of polymers in the environment, and they are already making adjustments to iPPO in hopes that it may eventually disappear altogether.

Bryce M. Lipinski, Lilliana S. Morris, Meredith N. Silberstein, Geoffrey W. Coates. Isotactic Poly(propylene oxide): A Photodegradable Polymer with Strain Hardening Properties. Journal of the American Chemical Society, 2020; 142 (14): 6800 DOI: 10.1021/jacs.0c01768