Researchers from the University of Houston have reported a new method to produce polyolefins from hydrocarbons, the common building block of plastics. The new method will address one of the biggest stumbling blocks to plastics recycling and will allow plastics to be produced from food oils and other natural substances.

Producing Plastics from Natural Substances
Eva Harth, director of the Welch-UH Center for Excellence in polymer chemistry, said the process addresses a long-standing need for industrial plastics producers, without requiring a new catalyst or expensive additives.

Polyolefins and derivative products such as polyethylene and polypropylene are used for everything from grocery bags to industrial pipes. Highly branched polyolefins are used in products that require softness or flexibility, such as grocery bags, while low branching is used to produce rigid plastics.

Traditionally, different catalysts have been required to spark differing levels of branching, meaning that only one type of plastic could be produced at a time. “You have to be specific about what material you are after, what type of branching you need,” Harth said.

Modulating Branching of Polyolefins
The new method allows branching to be modulated using a palladium catalyst with varying amounts of added aluminum chloride, which functioned as a Lewis acid; the aluminum chloride – an abundant and inexpensive substance – can be added at different points in the process, allowing the resulting polyolefin to contain differing branching properties.

The new process could address two growing issues faced by plastics producers – how to dispose of plastic waste in an environmentally friendly way, and how to reduce the use of oil and natural gas by instead using food oils and other natural substances.

Current polymers used in everyday materials – grocery bags, milk jugs, toys and medical equipment, for example – won’t readily mix when they are melted down for chemical recycling. “These new polymers could sit at the boundary, allowing plastics with disparate properties to be more easily recycled,” said R. Jones, a post-doctoral researcher with the Welch-UH Center.

The process will work with a variety of molecules to produce a polymer suggesting that the concept provides a new platform to produce plastics. And that platform could lend itself to producing a variety of functional plastics from natural oils and other molecular sources.

» Publication Date: 27/03/2020

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