Scientists have transformed used cooking oil into a variety of recyclable plastics that are extremely durable, and some were even strong enough to tow a car.
Turning inedible waste into useful polymers is a sustainable way to create new materials, say researchers in a new study published Nov. 28 in the journalJournal of the American Chemical Society.
“Waste streams represent a potentially attractive alternative to biomass-derived feedstocks. [to make plastics]”, the researchers wrote in the study.
One such waste stream is used cooking oil, almost3.7 billion gallons is generated every year. This waste oil is still used inlubricants, non-stick coatings And fuelbut most of it is thrown away anyway. In a new study, scientists have found a way to turn waste oil into useful plastic materials that are highly adhesive and recyclable.
Oil is made up of long chains of fatty acids bound to glycerol (also known as glycerin) molecules. The researchers chemically separated the oil molecules into parts and then converted the products into simpler molecules through a series of reactions.
Combining the final alcohol and ester molecules in a variety of ways has allowed researchers to synthesize a range of polyester plastics. (Ester molecules have a carbon atom doubly bonded to an oxygen atom, as well as one oxygen atom with a carbon side chain.)
Testing of the properties of the plastics, including their melting point and crystallinity, showed that these polymers are similar to low-density polyethylene (LDPE), a plastic commonly used in packaging and plastic bags.
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Polyesters were also sticky due to the oxygen atoms in the polymer, which form strong bonds with a number of materials. Unlike LDPE, which is a hydrocarbon containing only carbon and hydrogen atoms.
Two metal plates glued together with vegetable oil glue were strong enough to support hundreds of pounds of weight (left) as well as tow a car (right). (Image courtesy of Mahadas et al.)
The researchers tested the polymer's adhesive strength by gluing two stainless steel plates together. The slabs remained tightly glued together even when up to 270 pounds (123 kilograms) of weight were attached to them. Towing a four-door sedan on a slight incline with these glued-on steel parts was also no problem. This makes these polymers as strong or stronger than commercially available adhesives, which the team also tested.
These properties make these adhesives “ideal for applications in laminates and adhesives used in packaging, automotive components, medical devices, and electronics,” the researchers wrote.
Polyester plastics were easily recycled into their original components and then recycled back into plastic. Several recycling cycles had virtually no effect on the properties of plastics. Some plastics can also be recycled along with other common plastics such as HDPE and polypropylene.
“This work highlights the potential of inedible biomass waste as a renewable feedstock for… green alternatives to petroleum-based plastics,” the researchers wrote.
