In countless posts on this blog, we’ve extolled the benefits of plastics – they are strong, impermeable, mouldable, and, critically, long-lasting.
One of the greatest strengths of plastics materials is that they are stable for remarkably long periods of time – they don’t break down quickly when exposed to light, heat, or air. That’s a good thing in an era when plastics are widely used in cars, airplanes, construction, and many other applications where durability is important.
However, the blessing of robustness can also be a curse when a plastic item reaches the end of its life. Many plastic materials cannot be recycled, and, of those that can be recycled economically, only a small portion of the plastic produced makes it to a recycling facility. It is a paradox that has been facing the plastics industry for decades: how can we create a material that is strong, durable, and long-lasting, but which can easily be broken down and reused when it has reached the end of its useful life.
Luckily, as detailed in the Seattle Times in an article titled “Chemists in search of their Holy Grail: a plastic designed to die”, researchers are hard at work finding a solution to this paradox. Using a process called “polymer unzipping”, researchers are hoping to develop durable plastics materials that can disassemble into their constituent components when exposed to certain conditions.
Let’s take a closer look at how the polymer unzipping process works.
Regular plastics are made up of open-ended chains of stable polymers. These materials became popular specifically because they don’t break down. But what if scientists turned to unstable plastics, long overlooked by the industry, and found a way to temporarily make them stable?
Much of the work in this field involves finding ways to make polymer chains into loops which are stable in ambient conditions but which can easily be disrupted by heat, light, exposure to chemicals, or other means. Once the loops are disrupted, the molecular structure of the plastic material begins to quickly unravel into smaller, more stable units. These units, if returned to the manufacturer, are a pure feedstock, which could then be used to make new products.
Because the use of this method adds to the production costs of plastics, and the plastics must be returned to the manufacturer to be reused, it is likely that the technology will be applied to higher-value plastic items such as automotive parts and mattresses. Another possible use is in the realm of adhesives, where looped polymers could be released under certain conditions, resulting in glues that can be “turned off” to facilitate separation of parts.
At a time when plastics waste is on everyone’s mind, its seems as though its not a question of if self-destructing plastics will become economical and widespread, but when.