Low-density polyethylene

LDPE has SPI resin ID code 4
Schematic of LDPE branching structure

Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Dr John C. Swallow and M.W Perrin who were working for Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization.[1] Its manufacture employs the same method today. The EPA estimates 5.7% of LDPE (resin identification code 4) is recycled in the United States.[2] Despite competition from more modern polymers, LDPE continues to be an important plastic grade. In 2013 the worldwide LDPE market reached a volume of about US$33 billion.[3]

Despite its designation with the recycling symbol, it cannot be as commonly recycled as No. 1 (polyethylene terephthalate) or 2 plastics (high-density polyethylene).[4][5]

  1. ^ Dennis Malpass (2010). Introduction to Industrial Polyethylene: Properties, Catalysts, and Processes. John Wiley and Sons. pp. 1–. ISBN 978-0-470-62598-9.
  2. ^ "Municipal Solid Waste Generation,n word and Disposal in the United States" (PDF). EPA.gov. 15 November 2016.
  3. ^ "Market Study: Polyethylene LDPE (2nd edition)". Ceresana.
  4. ^ Brady, Angela (28 December 2018). "How to Recycle Number 4 Plastic". San Francisco Chronicle.
  5. ^ "Exactly What Every Plastic Recycling Symbol Really Means". Good Housekeeping. 18 February 2022.