Recycling of Polymers and Composites

Abstract

Abstract Each year, more than 25 million vehicles reach the end of their service life throughout the world, and this number is rising as the number of vehicles on the road is increasing. In the United States, over 95% of the more than 10 million vehicles scrapped annually enter a comprehensive recycling infrastructure that includes auto parts recyclers (dismantlers), remanufacturers, and material recyclers (shredders). Over 75% of the automotive materials, primarily metals, are profitably recycled. Automobiles are the largest source of recycled ferrous scrap for the iron and steel industry. The scrap processors recover metal scrap from automobiles by shredding the obsolete automobile hulks, along with other obsolete metal‐containing products and recovering the metals from the shredded material. The nonmetallic fraction that remains—commonly called shredder residue —constitutes about 25% of the weight of the vehicle, and most of it is landfilled. In the past two decades, research and development has been undertaken to enhance the recycle rate of end‐of‐life vehicles ( ELVs ), including improving dismantling techniques and remanufacturing operations. However, most of the effort has been focused on developing technology to separate and recover the polymers from shredder residue. To make future vehicles more energy efficient and to meet the new Corporate Average Fuel Economy ( CAFE ) regulations, more lightweighting materials—primarily polymers and polymer composites, high strength steels, and aluminum—are being used by the automobile industry. The nonmetallic materials increase the percentage of shredder residue that must be disposed of, compared with the percentage of metals that are recovered. Therefore, recycling of automotive polymers will be more important in the future. In addition, recycling the polymers and the composites has the following additional benefits: (i) conserves valuable resources of materials and energy, including the energy consumed in manufacturing automotive materials; (ii) provides lower cost materials to industry; (iii) reduces the amount of waste going to the landfill; and (iv) reduces greenhouse gas ( GHG ) emissions. The future will also bring an increase in hybrid and electric vehicles. This will introduce new materials for disposal, including batteries. Recycling the new materials presents technical and economic challenges to the existing automotive recycling infrastructure. New technologies will be required to sustain and maximize the ultimate recycling of the vehicles.