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Chemistry > Organic Chemistry > LDPE – Low-Density Polyethelene – Properties and Uses
Organic Chemistry

LDPE – Low-Density Polyethelene – Properties and Uses

Introduction to LDPE- Low-Density Polyethelene

Low-density polyethelene (LDPE) is high clarity and chemically inert polymer that is widely used, owing to its flexibility, barrier properties, good impact strength, and stress crack resistance. It is also one of the more economic polymers available.

A branched polymer, Low-density polyethylene, or LDPE, is one that has its processing and end-use properties primarily ascertained by its molecular weight distribution (MWD), long-chain branching distribution (LCBD), and short-chain branching distribution (SCBD). Read ahead to know more about its properties and multitude of uses.

LDPE

 

Properties of LDPE?

  • It is a homopolymer; made of a single monomer, ethylene.
  • The polymer density is controlled by the kind of branching it has.
  • LDPE contains a mix of long branched chains and short branched chains.
  • It is produced by undergoing a high-pressure process.
  • LDPE is characterized by 50-65% crystallinity, as the packing of the molecules is not the tightest.
  • It is translucent in appearance, as a result of the crystallinity. However, very thin foils can be transparent.
  • It is not very easy to bond.
  • LDPE is sufficiently malleable and elastic, able to undergo significant elongation before breakage.
  • It is fairly puncture-resistant, between -40 C to 90 C.
  • LDPE is susceptible to stress-cracking beyond a point.
  • It has a sufficient moisture barrier.
  • Its oxygen barrier is low.
  • It has significant chemical resistance.
  • It is a flammable material.
  • LDPE softens at a relatively low temperature of approximately 100°C. In fact, for some grades, the temperature could be even lower.
  • It undergoes high thermal expansion.
  • Its weathering resistance is not very good.
  • ItS processing can easily take place by practically all thermoplastic methods.
  • It has food-grades available as well.

Uses OF LDPE

LDPE’s first experimental preparation took place in the 1930s. It was brought to the commercial forefront as a consequence of its widespread use during the Second World War in the high-frequency radar cables.

Its success on the commercial front stems from the fact that this thermoplastic is very economical and has good moisture resistance. Additionally, it comes in various levels of flexibility depending on the production process that it had undergone.

As a high-branched polymer, it does have lower density, hardness, stiffness, or strength when compared to HDPE, which might appear to be shortcomings. However, this is exactly what contributes to the higher ductility of the material, which is a very important feature.

This polymer is typically useful for making packing material such as wrapping foils, foam, trays, and plastic bags (the soft and non-crackly kind), both for food packaging, and otherwise.

This polymer plays an important role as one of the multiple layers of plastic in milk cartons. It is also useful for making bottles, pipes, garbage bags, utensils, processing material, wire insulation, and even toys. It is also useful as a thin protective layer over the paper, other plastics, or textiles.

LDPE is, however, not suitable for cook-in packs, as it softens at around (and sometimes lower than) 100°C. However, this makes it readily heat-sealable.  It has also useful in the medical sphere, as it is effective for sterile blister packs, and as drug packaging.

This polymer is non-polar and its use for printing and lamination cannot take place, without undergoing surface-treatment. Overall, LDPE, a very affordable polymer to purchase or produce, has found multiple uses across the board.

Solved Question for You

Q1. Which of the following is not a property for LDPE

(a) Its oxygen barrier is high.

(b) Comprises a mix of both long branched and short branched chains.

(c) Undergoes high thermal expansion.

(d) It is flammable in nature.

A1. The correct answer is option (a). This is because the oxygen barrier of LDPE is low rather than high.

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