According to the latest issue of “Science” magazine, a team led by researchers from Virginia Tech in the United States has developed the world’s first bar of soap made of plastic. The new method can upcycle plastics into a class of high-value chemicals called surfactants.
Fill the flask with wax produced from waste polyethylene and polypropylene, heat it in an oil bath, oxidize the wax under the action of airflow, and produce fatty acid through catalytic oxidation.
Plastic and soap have little in common in terms of texture, appearance, or how they are used, but there is an unexpected link between the two at the molecular level: the chemical structure of polyethylene (one of the most commonly used plastics in the world today) Fatty acids, the chemical precursors of soap, are surprisingly similar. Both materials are made of long carbon chains, but fatty acids have an extra atomic group at the end of the chain. This similarity means that polyethylene can be converted to fatty acids.
The researchers built a small oven-like reactor that generates temperatures high enough at the bottom to break the polymer chains and cools enough at the top to prevent the chains from breaking. After pyrolysis, they collected the residue and found it to be a wax composed of “short-chain polyethylene.”
After adding several steps, including saponification, the team created the world’s first bar of plastic soap. It’s a new route to the plastics upcycle that doesn’t use new catalysts or complicated procedures.
Although PE was the plastic that inspired this project, the upcycling method also works with another plastic called PP (Figure 3). These two materials make up the majority of the plastics consumers encounter every day, from product packaging to food containers to fabrics. An exciting feature of this paper’s new upcycling method is that it can be used for both types of plastic, meaning there is no need to separate the two. This is a major advantage over some recycling methods in use today, which require careful sorting of plastics to avoid contamination. Since the two plastics are so similar, this sorting process can be very difficult.
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