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Low density polyethylene

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Low density polyethylene

LDPE has SPI resin ID code 4

Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by 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 (recycling number 4) is recycled.[2] Despite competition from more modern polymers, LDPE continues to be an important plastic grade. In 2009 the worldwide LDPE market reached a volume of US$22.2 billion (15.9 billion).[3]

Properties

LDPE is defined by a density range of 0.910–0.940 g/cm3. It is not reactive at room temperatures, except by strong oxidizing agents, and some solvents cause swelling. It can withstand temperatures of 80 °C continuously and 95 °C for a short time. Made in translucent or opaque variations, it is quite flexible, and tough but breakable.

LDPE has more branching (on about 2% of the carbon atoms) than HDPE, so its intermolecular forces (instantaneous-dipole induced-dipole attraction) are weaker, its tensile strength is lower, and its resilience is higher. Also, since its molecules are less tightly packed and less crystalline because of the side branches, its density is lower. LDPE contains the chemical elements carbon and hydrogen.

Chemical resistance

Applications

A GEECO bowl, c.1950, still used in 2014.

LDPE is widely used for manufacturing various containers, dispensing bottles, wash bottles, tubing, plastic bags for computer components, and various molded laboratory equipment. Its most common use is in plastic bags. Other products made from it include:

See also

References

  1. ^ Dennis Malpass (2010). Introduction to Industrial Polyethylene: Properties, Catalysts, and Processes. John Wiley and Sons. pp. 1–.  
  2. ^ "Municipal Solid Waste Generation, Recycling, and Disposal in the United States". EPA.gov. 
  3. ^ "Market Study: Polyethylene LDPE". Ceresana Research. 
  4. ^ "Plastic Properties of Low Density Polyethylene (LDPE)". Dynalab Corp. 
  5. ^ LDPE products and applications. Exxon Mobil Corporation
  6. ^ DOW LDPE 5004I. IDES – The Plastics Web

External links

2010_MSW_Tables_and_Figures_508.pdf. epa.gov

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