(585g) Molecular Recycling of Mixed Plastics Based on Dissolution/Precipitation

Plastics are widely used across industries such as food, beverage, textile, healthcare, automotive, aerospace, construction, agriculture, and petroleum. Only a small fraction of the plastics produced is being recycled, with the great majority landfilled or released into the environment. There is great interest nowadays in increasing the recycling of plastic waste. Mechanical recycling is currently used to recycle plastic waste, however, this method is efficient only for homogeneous and non-contaminated plastic waste, and for easily identifiable objects such as bottles made of PET or HDPE. A solution for recycling many of the plastics which mechanical recycling fails to process comes from chemical recycling, which typically involves the deconstruction of polymers to monomers or to intermediates that can be used as chemical feedstock or fuel. These, however, result in undesirable greenhouse gas (GHG) emissions.

Our research advances solvent-based recycling, whereby polymers are selectively dissolved and precipitated to achieve separation and recovery. Because the polymer chains do not break, this presents a promising, low-GHG methodology for recycling waste plastic. Through the dissolution/precipitation method, desirable types of polymers can be separated from mixtures or blends, purified from additives or fillers, and obtained in a form suitable for reprocessing, without negatively affecting the properties of the original polymers. Examples are presented on mixed plastics separation employing dissolution/precipitation with environmentally responsible solvents. Processing conditions for efficient recovery of polyolefins are discussed.