polymers (2)

Recycling Green Plastics...

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Credit: Cell Reports Physical Science (2024). DOI: 10.1016/j.xcrp.2024.101783

Topics: Biochemistry, Chemistry, Polymer Science, Polymers

Scientists at King's College London have developed an innovative solution for recycling single-use bioplastics commonly used in disposable items such as coffee cups and food containers.

The novel method of chemical recycling, published in Cell Reports Physical Science, uses enzymes typically found in biological laundry detergents to "depolymerize"—or break down—landfill-bound bioplastics. Rapidly converting the items into soluble fragments within just 24 hours, the process achieves full degradation of the bioplastic polylactic acid (PLA). The approach is 84 times faster than the 12-week-long industrial composting process used for recycling bioplastic materials.

This discovery offers a widespread recycling solution for single-use PLA plastics, as the team of chemists at King's found that in a further 24 hours at a temperature of 90°C, the bioplastics break down into their chemical building blocks. Once converted into monomers—single molecules—the materials can be turned into equally high-quality plastic for multiple reuse.

The problem with 'green' plastics

Current rates of plastic production outstrip our ability to dispose of it sustainably. According to Environmental Action, it is estimated that in 2023 alone, more than 68 million tons of plastic globally ended up in natural environments due to the imbalance between the huge volumes of plastics produced and our current capacity to manage and recycle plastic at the end of its life. A recent OECD report predicted that the amount of plastic waste produced worldwide will almost triple by 2060, with around half ending up in landfills and less than a fifth recycled.

An enzyme used in laundry detergent can recycle single-use plastics within 24 hours, King's College London.

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B-TENG...

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Gentle breeze: illustration of the B-TENG triboelectric nanogenerator, which harvests electricity that is generated by fluttering polymer strips. (Courtesy: Xin Chen/Xiaojing Mu/Ya Yang)

Topics: Applied Physics, Nanotechnology, Polymers, Research

A new low-cost nanogenerator that can efficiently harvest electrical energy from ambient wind has been created by Ya Yang at the Beijing Institute of Nanoenergy and Nanosystems of the Chinese Academy of Sciences and colleagues. The team reports that the device achieves high electrical conversion efficiencies for breezes of 4–8 m/s (14–28 km/h) and says that it could be used to generate electricity in everyday situations, where conventional wind turbines are not practical.

As the drive to develop renewable sources of energy intensifies, there is growing interest in harvesting ambient energy in everyday environments. From breezes along city streets to the airflows created as we walk, the mechanical energy contained in ambient wind is abundant. The challenge is to harvest this every in an efficient and practical way. This has proven difficult using existing technologies such as piezoelectric films, which operate at very low power outputs.

Yang’s team based their new design around two well-known phenomena in physics. The first is the Bernoulli effect, which causes the fluttering of two adjacent flags to couple. If separated by a very small gap, the flags will flutter in-phase, while at slightly larger separations, they flap out-of-phase, and symmetrically about a central plane. The second is the triboelectric effect – the familiar phenomenon behind the “static electricity” that is created when different objects are rubbed together and then separated – resulting in opposite electrical charges on the objects and a voltage between the two.

Fluttering polymer ribbons harvest electrical energy, Physics World

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