A team of researchers at Lawrence Berkeley National Laboratory has been studying large-scale production of a new plastic, poly(diketoenamine). It has all the useful properties of traditional plastics but, unlike traditional plastics, PDKs can be recycled indefinitely with no loss in quality. The team found that PDK-based plastic could quickly become commercially competitive with conventional plastics, and the products will get less expensive and more sustainable as time goes on.
The problem with traditional plastics is that so far, more than 8.3 billion tons of them have been produced, and the vast majority of it has ended up in landfills or being burned in waste incineration plants. Only a small proportion of plastics are recycled “mechanically,” meaning they are melted down and re-shaped into new products. Unfortunately, this technique is limited because plastic resins are mixed with many different additives for different textures, colors, and capabilities, such as pigments, heat stabilizers and flame retardants.
So, when many different plastics are melted down together, the plastic polymers get mixed with many potentially incompatible additives, resulting in a new plastic with much lower quality than those made using virgin resin from raw materials. As such, less than 10% of plastic is mechanically recycled more than once, and recycled plastic usually must contain a significant amount of virgin resin to compensate for the dip in quality.
PDK plastics sidestep this problem by using resin polymers that easily break down into individual monomers when mixed with an acid. The monomers can then be separated from any additives and collected to make new plastics without any losing any performance or quality. The team’s earlier research shows that this “chemical recycling” uses little energy and creates few CO2 emissions. It can also be repeated indefinitely, creating a completely circular material lifecycle unlike the current one, which is essentially a one-way ticket to waste.
“The next step is to determine how much it will cost to scale it up, what the affect will be on energy use and emissions, and how to get there from where we are today,” says Brett Helms, a staff scientist at Berkeley Lab.
Recycled PDKs are already drawing interest from companies sourcing plastics. The Berkley team has been conducting market research and meeting with industry people and have determined that the best initial application for PDKs are markets where manufacturers will get their products back at the end of their lifespan, such as the auto industry (through trade-ins and take-backs) and consumer electronics (through e-waste programs). These companies can then reap the benefits of 100% recyclable PDKs, namely sustainable branding and long-term savings. Plus, some countries plan to charge significant fees on plastic products made of on non-recycled materials. That should give companies a strong incentive to move away from virgin resins and drive the demand for recycled plastics.
The team is also working on way to improve the process by using microbe-made precursors. The process currently uses industrial chemicals but was initially designed with microbes in mind. This would let nearly the entire polymer be made from plant material fermented by engineered microbes.
PDK technology is available for licensing and collaboration. If interested, please contact Berkeley Lab’s Intellectual Property Office.