Another important research topic in plastics is the challenge to recycle plastic waste. According to researchers at the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) (https://www.sciencedaily.com/releases/2019/05/190507110452.htm), the challenge with recycling plastic material arises from the fact that as plastics with different chemical compositions are mixed together to form the end-product, it is hard to tell which properties will be inherited from the original plastics. Thus, the recovery of the original monomers becomes an unknown equation. Researchers have developed a new plastic material called poly(diketoenamine), or PDK, with reversible bonds that can be recycled by dunking the material in a highly acidic solution. The acid breaks the bonds between the monomers of the PDK to separate the chemical additives that would otherwise prevent the plastic to be upcycled. PDK can be used in adhesives, phone cases, watch bands, shoes, cabling, and more. Further research is planned to use PDK plastics in applications such as textiles, additive manufacturing, and foams.