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LDPE Vs. HDPE

LDPE Vs. HDPE
LDPE and HDPE are two different types of plastic. This ScienceStruck article provides you with a comparison chart to let you know about the differences between them.
ScienceStruck Staff
Fast Fact
The Al-Sejeel complex, which was supposed to manufacture 430,000 tons/year of linear low-density polyethylene (LLDPE), 760,000 tons/year of polypropylene (PP), 1.4 m tons/year of ethylene, 1.04 m tons of high-density polyethylene (HDPE), and 550,000 tons of low-density polyethylene, has been put on hold by Qatar for an alternate project.
The word plastic encompasses a wide variety of synthetic materials, mostly derived from petrochemicals. Scientifically, they are called organic polymers, and are available in a variety of types, the most common one being polythene or polyethylene (PE). This has further classifications, categorized according to the change in the molecular structure of organic compounds. Two of its common structures are low-density polyethylene (LDPE) and high-density polyethylene (HDPE), which vary in terms of structure, density, and characteristics. They are widely used in regular domestic applications. In the paragraphs below, you will understand the difference between HDPE and LDPE.
LDPE
LDPE
Structure of LDPE
  • It is abbreviated from low-density polyethylene.
  • It has a natural, milky-white color and is translucent.
  • It is resistant to chemicals and has a strong impact.
  • It has a good stress crack resistance, and a good vapor barrier as well.
  • It has excellent alcohol barrier properties too.
HDPE
HDPE
Structure of HDPE
  • It is abbreviated from high-density polyethylene.
  • Like LDPE, its color is also a natural milky white, and as per its density, it can be translucent or semi-translucent.
  • It has a very strong impact as well, and excellent chemical resistance.
  • It is resistant to stress cracking, but has a poor gas barrier.
  • Like its counterpart, it has a good moisture barrier.
Factors of Differentiation
LDPE HDPE
Structure It has a good branching structure, including both short and long chains. The chains are not packed into the crystal structure, and this results in mediocre intermolecular forces. It has a very low amount of branching and has strong intermolecular forces.
Density It has a low density of course, the range being between 0.910 and 0.925 gm/cm3. It obviously has a high density, the value being within the range of 0.941 to 0.965 gm/cm3.
Applications
  • Drop cloths
  • Liners
  • Plastic bags
  • Film wraps
  • Plastic bottles
  • Tarps
  • Construction
  • Agriculture
  • Surface protection
  • Water bottles
  • Food containers
  • Furniture
  • Pipes
  • Lumber
  • Storage tanks
  • Automobile components
  • Toys
  • Chopping boards
  • Canal liners
  • Liners for oil tanks
  • Containment liners for industrial ponds
  • Plastic bottles
Strength It has a high ductile nature and mediocre tensile strength. It is not puncture-resistant. It has a high tensile strength. It is dense, has a high resistance to puncture, and is resistant to UV rays too.
Production It is produced by means of free radical polymerization. It is produced by using catalysts, like silica, metallocene, or chromium.
Flexibility It is very flexible, and conforms well to surfaces, though it is soft and less rigid, compared to HDPE. It is also flexible and stretches well, but not as much as LDPE; it is tougher, less malleable, and more rigid.
Melting Point
The average melting point is 221 to 239 °F. The average melting point is 248 to 356 °F.
Points to Remember
  • Both LDPE and HDPE have a host of common properties.
  • Both are sterilized through gamma radiation.
  • While using them in the manufacturing process, they are thermoformed.
  • HDPE is approved by the FDA, hence it passes the safety factor.
  • LDPE is also reviewed to be safe, as it is used to manufacture food containers.
  • Recycling them both is done using a method called pyrolysis.
The chemical bonds that bind plastics make them durable and provide them with a tendency to degrade slowly. However, it is also true that certain plastics contain many additives, which increase their toxic content. They must be used and disposed carefully, considering their harmful effects on the environment.