To address the plastic environmental crisis, chemists have developed a new polymer with ample strength in a marine setting that degrades by ultraviolet radiation. The plastic has the mechanical properties required by commercial fishing gear. If it eventually gets lost in the aquatic environment, the material can degrade on a realistic time scale.
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.
The new plastic — called isotactic polypropylene oxide (iPPO) — was discovered originally in 1949 but the mechanical strength and photodegradation of the material was unknown until now. The high isotacticity (enchainment regularity) and polymer chain length of the new material makes it distinct from its historic predecessor and provides its mechanical strength. 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 during the process. The rate of degradation is light-intensity-dependent but under laboratory conditions, the polymer chain lengths degraded to a quarter of their original length after 30 days of exposure.
Ultimately, the scientists want to leave no trace of the polymer in the environment. There is literature precedent for the biodegradation of small chains of iPPO that could effectively make it disappear but ongoing efforts aim to prove this.