Recently, researchers at the University of California, Berkeley invented a new chemical process that can recycle waste plastic bags (mainly polyethylene PE) and convert them into more valuable adhesives, realizing the upgrade of polyethylene Recycling.
According to reports, the researchers used a catalyst based on ruthenium (gold balls in the middle) to add specific chemical groups (in this case, OH (red)) to the polyethylene polymer chain to form an oxidized poly Vinyl. It can be firmly attached to the metal and retains the unique plastic characteristics of polyethylene. Researchers have made 11 attempts and it is difficult to separate water-based latex paint from Ox-LDPE (Ox-LDPE). Previously, latex paint was basically difficult to adhere to ordinary plastics.
"Polyethylene chains usually have 2,000 to 10,000 carbon atoms, and each carbon atom has two hydrogen atoms-in fact, it is an ocean of CH2 groups called methylene groups. We consulted the literature , Looking for active catalysts that we can find for functionalization of methylene positions." The researchers said.
Considering that solid recycled plastics need to be melted, this requires that the catalyst used for polyethylene recycling and modification can work in high temperature and non-polar solvents in order to be mixed with non-polar polyethylene. The researchers studied a ruthenium-based catalyst (polyfluororuthenium porphyrin) that can meet these requirements and can add OH groups to the polymer chain without breaking the polymer chain by the highly active hydroxyl groups.
The researchers found that catalysis chemically changes less than 10% of the polymer, but it greatly enhances its ability to adhere to other surfaces. The improvement of polyethylene`s adhesion has potential for application-for example, artificial hip and knee implants usually combine polyethylene with metal parts, and the improvement of polyethylene`s adhesion can make it better Ground adheres to the metal. Functionalized polyethylene can be used for wire coating, to provide glue to hold other polymers together (such as milk cartons), or to make more durable plastic and metal composite materials, such as toys.
The researchers said that the current process is not economical enough in industry, but it can be improved. This research and development also means that other catalysts can work with other types of plastics (such as polypropylene in recycled plastic bottles) to produce economically attractive, high-value products.
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