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TIDBITS FROM AAAS

THE AAAS, the American Association for the Advancement of Science, and its weekly Science magazine share knowledge with an audience broader than readers of pure scientific journals. These tidbits gleaned from Science, April 22, 2019, have a recycling theme: plastic bottles and converted U-2 spy planes.

Enhancing Plastic Recyclability. It is a sad observation that 90 percent of plastics in the U.S. end up in landfills. Yet Alex Fox reports promising news: “A New Kind of Plastic Could Change That.”

Fox writes, “Most plastics have a chemical history that makes starting a new life a challenge. The dyes and flame retardants that make them perfect for, say, a couch cushion or a bottle of detergent make them tough to transform into a desirable end product.”

Image by Jie Zhao/Corbis via Getty Images from Science, April 22, 2019.

I recall a similar situation exists with automotive tires: The process of vulcanization cannot be undone; a tire’s elastomers, carbon black, silica, metallic and textile reinforcements, and chemical additives are combined forever. Feasible uses for old tires include burning them for industrial heat or grinding them for inclusion in future roadways.

By contrast, Fox writes of this new plastic, “The chemical bonds in the new, as-yet-unnamed variety make it easy to extract the building blocks, called monomers, used by manufacturers to make plastic polymers.”

Vitrimer, a glasslike plastic developed in 2011, proved the key. Tweaked, it results in new chemical linkages called dynamic covalent diketoenamine bonds that require less energy to break than those of conventional plastics.

Conventional plastic recycling calls for a catalyst acting at high temperature. The new process needs only room-temperature water and a strong acid. Science reports, “The recovered material’s quality is on par with the unadulterated resin used to make plastics.”

In a deft balancing act, researchers had to ensure that the plastic wouldn’t start decomposing ahead of schedule. The powerful acid required isn’t something likely to be encountered in ordinary use.

Another tire-related story comes to mind: Earliest rubber compounds were known to revert to gummy masses depending on ambient conditions. This was particularly problematic in one of their first applications: rubberized apparel.

Science identifies that the new plastic material was devised by a team of researchers at California’s Lawrence Berkeley National Laboratory. Results were reported online in Nature Chemistry, April 22, 2019.

Recycling U-2 Spy Planes. In “The Overworld,” Eli Kintisch describes NASA’s ER-2, a modified version of the Lockheed U-2 high-altitude reconnaissance aircraft operated by the USAF and previously flown by the CIA. This time around, its mission is to sample particles, gases, and moisture in the stratosphere.

The troposphere is the bottom 10 miles or so of Earth’s atmosphere. Above this lies the 20-mile-thick layer of the stratosphere, which includes the Ozone Layer in its lower portion. The Ozone Layer makes life possible on Earth by absorbing much of the sun’s UV radiation.

Image by C. Bickel/Science from Science, April 22, 2019.

Beginning at around 46,000 ft., the Ozone Layer is low enough to be reached by “overshoots” of weather, and also possibly by Ozone-Layer-damaging pollutants. Next year, NASA will investigate this with DCOTSS, the Dynamics and Chemistry of the Summer Stratosphere project.

The ER-2 is a modified Lockheed U-2. Image from NASA/Carla Thomas.

The ER-2 can probe altitudes to nearly 80,000 ft., where the atmosphere is rare enough to make flight a difficult proposition. Its predecessor U-2 is known as the Dragon Lady, a moniker earned by the craft’s temperament. Kintisch writes, “To prevent the plane from stalling or creating destabilizing shock waves, for instance, ER-2 pilots must stay within a narrow range of speed dubbed the ‘coffin corner.’ ”

The DCOTSS research goal, Kintisch notes, “will be collecting data from the North American monsoon anticyclone, a continental-size atmospheric gyre [spiral or vortex] that partially confines moist summer air over North America. The gyre is fed by warm air from the Gulf of Mexico, which pours across the Midwest, fueling thunderstorms that feature some of the world’s most intense rain, lightning, and convection strong enough to puncture the tropopause.”

At least intrepid NASA ER-2 pilots won’t encounter plastic bottles at that altitude. ds

© Dennis Simanaitis, SimanaitisSays.com, 2019

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