First step towards more effective plastic recycling

Hello dear friends.

The plastics industry already has a long history of producing various types of polymers, those large molecules that are made up of smaller units called monomers, which are joined together by covalent bonds forming long chains of high molecular weight, examples of which are materials such as polyethylene, polypropylene, polystyrene and polyurethane, among others, being today the different synthetic polymers the basis of all kinds of plastic materials.

One option for recycling plastics is the recovery of monomers. Source: @emiliomoron, contains a public domain image.

However, although the formation of these macromolecules through polymerization, which is basically assembling a long chain through the repetition of simple molecular units, is quite well known and has been very well investigated, giving us the large number of plastic materials that we know; The truth is that performing the reverse process and separating these macromolecules into their individual units or blocks, a process called depolymerization, has been little studied, so there is no efficient method to recover these individual building blocks, or monomers.

Example of the polymerization of styrene. Source: image made in powerpoint .

Certainly there are several reasons why scientists have not paid much attention to the depolymerization process, on the one hand it is an extremely complex process to break the chains that bind the monomers, since it depends on the type of compound and the process used in its manufacture, In addition to the fact that this reverse process requires much more energy than that used in the manufacture of the starting compound, and current processes provide lower quality products, making it only usable in lower value products, which has led to the exploration of this option is economically unfeasible.

But a team of polymer materials researchers at ETH Zurich has managed to break down polymers into their individual components and recover more than 90% of them, which would be an important step on the way to a true plastics recycling method. The results of the study have just been published in the Journal of the American Chemical Societycall_made, and in said study, this team reports having achieved a catalyst-free depolymerization of several linear polymethacrylates, decomposing almost 92% of them into their constituent monomers, being able to be recycled to be used in other applications.

The new method allows the depolymerization of the monomers and their polymerization again. Source: image made in powerpoint .

The polymers that were broken down were produced by a new polymerization technique called reversible addition fragmentation chain transfer (RAFT) polymerization, a method that is attracting much interest in the industry as it produces polymer chains with a uniform length, and through this method, this group of researchers managed to locate radicals at the end of the polymerization chain, which allowed depolymerization to be triggered.

The advantage of this new method is that the recovered monomers can be used to reconstruct the same polymer from which they were obtained or an insoluble gel that can also be subjected to depolymerization, and the products created from these have the same characteristics as the original ones. .

Although much more research is still needed to develop the method and scale it to an industrial level, it already offers some hope in the search for solutions for plastic pollution, even this would be a long-term solution, since it would be a way to recover the polymer monomers manufactured in this way, not being used for the amount of plastic waste that already pollutes our environment. But we must bear in mind that these are the first steps towards the production of truly recyclable plastics, compared to the number of studies that have only addressed polymerization methods without contemplating the reverse process to recover these materials.

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Thanks for coming by to read friends, I hope you liked the information. See you next time.

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