A new paper, published in Science, is understandably making headlines around the world. Describing a new type of polymer, the research team's senior author said that it could be “chemically recycled and reused, in principle, infinitely”. So what’s the story behind this grandiose-sounding claim?
Some plastics can be recycled, and some cannot. PET, a common variant, can be, as can polystyrene; they have weak chemical bonds, and as such can be melted down. This, of course, takes plenty of energy, and products are infrequently 100 percent recyclable. Conversely, thermosetting plastics have such strong chemical bonds that it’s virtually impossible to recycle them.
Even for those that can be, logistics often prevent them from being recycled in the first place. Plenty of plastic accumulates in landfill sites, or in the oceans.
In light of all this, a team of chemical wizkids from Colorado State University have spent considerable time trying to create a greener, entirely and easily recyclable form of plastic, but one that still has the lightweight, strong, multipurpose nature of regular plastics.
Technically, they’ve been looking at polymers in general – comprised of long chains of repeated molecular components – which include rubbers, ceramics, and fibers. Plastics, understandably, are the focus of much of the accompanying rhetoric, considering that plastic pollution, a phenomenon we’re still scrambling to comprehend, is an environmental and ecological scourge.
At the same time, these ocean-dominating fragments are made from oil, which certainly doesn’t help shrink our carbon footprint.
The team briefly looked at other options for creating a “circular plastic economy”, one in which we keep the plastic in use for as long as possible, ideally forever. They suggest that none of them are sustainable, including biodegradable plastics, which, although far greener than current options, mean we still “fail to recover building block chemicals” and could still cause unintended environmental troubles.
The key issue for them was this permanent, extremely wasteful loss of materials. In order to circumvent it, they’ve been playing about with various chemical configurations, hoping to find a plastic where all its individual components are easily reobtained from the product, and can be used again.
They made a breakthrough in 2015, but the material wasn’t as plastic-like as they’d hoped, and it required exhaustive engineering conditions to create. Now, in 2018, they’ve made a considerable step up.
This new monomer (the individual, repeated component) can be easily turned into a polymer without using a solvent, at room temperature, and in the space of a few minutes, with just a sprinkling of a catalyst. It’s a remarkably energy-efficient method, and resource-light. As a polymer, it has all the mechanical strength and durability you’d hope for in a plastic.
Instead of throwing it into a heater to break it down, all that’s needed here is another catalyst, which triggers its depolymerization within mere moments. From this resultant gloop, you can once again polymerize it, with no significant waste observed. This “circular monomer-polymer-monomer cycle” is what the infinity claim is based on.
So far, this has only been conducted in a laboratory setting, and it’s unclear how easy it’ll be to scale this up. This is, at present, a proof-of-concept design, but one with enormous potential, hinting at a world where convenience doesn't also mean the wasteful destruction of the environment.
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