Recycling of Flexible Plastic Films: Emergent Technologies

Plastic is a valuable material for packaging of food and pharmaceuticals, protective wrappings in construction and agriculture, and fluid storage. Flexible plastic or plastic film waste from packaging, agriculture, and construction applications grows at a rate of at least 92 million metric tons a year, is considered challenging to recycle, and is typically landfilled. In recent years, there have been great advancements in plastic recycling technology in order to deal with the global challenge of plastic waste buildup and support legislation from a local to national level to implement recycling. This work highlights the most recent advancements in plastic film recycling. Plastic films are mono- or multilayered based on what their applications will be, with multilayer multimaterial films being the more challenging feedstock for recycling. Mechanical recycling cannot easily process flexible films. Pyrolysis can use polyolefin-based film as feedstock but is not practiced at scale to match the rate of plastic film waste generation, and incineration can recover energy from film feedstock but is not recycling plastic. This has motivated the development of new recycling technologies designed around plastic films. Better characterization technologies to identify film compositions in municipal waste streams have been key to sorting out film feedstock for mechanical recycling and the baling of flexible plastic waste, but they struggle with multilayer films and black plastic. Compatibilization enables the recycling of mixed plastic waste but requires polymer compositions for selecting specific compatibilizers. Dissolution-precipitation recovers individual types of polymers from multilayer films and, at the same time, can purify polymers from additives or contaminants, but requires intense solvent processing and associated energy. Delamination of multilayer films can separate and recover solid films of polyolefins at relatively low amounts of solvent but requires quality feedstock to be efficient. Both dissolution-precipitation and delamination recycling of films recover the original polymer molecules and maintain their embodied energy, hence support circularity. In the case of PET-containing films, depolymerization to recover PET monomers offers opportunities to recycle challenging film feedstock.