Most people would agree that recycling plastic is a good idea. Not only are the environmental effects of producing plastics lessened – in many cases recycling can make financial sense for producers too. However, recycling is far from perfect today.
The problem lies in the fact that many consumer plastics contain additives specifically designed to serve a specific function. For example, additives can be used to change the optical properties of a plastic, alter its stiffness, or change other material properties.
These additives, which come in a variety of chemical forms, often bind tightly to polymers (the long hydrocarbon molecules plastics are made from) when plastics are produced. While this tight binding has traditionally been seen as essential for the additives to be effective, it makes it difficult to remove the additives when the plastics are recycled. For most of the history of recycling, recycled plastics have been made of a mix of different types of plastics with different additives. The result is a recycled product that is not as pure as the original plastic constituents. This reduces the value of the recycled plastic because it can often only be used to produce relatively low-grade products (the use of plastics in such applications is known as “downcycling”.
However, change is on the way. According to Forbes magazine, researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, located in California, have been developing a new type of plastic which is designed to be recycled indefinitely while still allowing for the use of essential additives. The new material, known as polydiketoenamine (PDK), and the associated additives can be disassembled at the molecular level by use of a strong acid. The different types of molecules (polymers and different types of additives) can then be sorted and used as raw materials to make new plastics products.
Given the volume of consumer plastics containing high-tech additives (think smart-phone cases, computers, and other high-performance plastics), which cannot currently be recycled, if this technology could be deployed on a commercial scale, it could make recycling much more attractive to manufacturers. In addition to improving the consumer image of the company, the additives and high-tech polymers recovered by the new technique could be reused, saving companies a lot of money.
Although the research is promising, its economic viability has not yet been demonstrated. Like so many high-tech plastics products, it remains to be seen whether PDK has what it takes to compete in the modern plastics market.